History of Psychology (Section 3)

History and Theory of Psychology: An early 21st century student's perspective

Bridging The Gap: British Associationism, Psychophysics, and the Founding of a Discipline

The descriptive term "bridging the gap" refers to the monistic strivings of the transitional period to be covered in this Section (roughly 1749-1890s). With historical hindsight, this period can be viewed generally as a set of varied attempts to bridge the gap between previous 17-18th century philosophical inquiry into mentality and the rise of a late 19th century experimental-science of the mind. More particularly, however, each of the main investigative movements involved in this transition had their own specific contemporaneous concerns as follows:

British Associationists	real and perceived world; simple and complex ideas
Psychophysicists	measurement of the mental-physical world relation
Wundt's Laboratory	measurement of Sensory, Ideational, Affective elements
Wundt's Students	measurement of higher mental processes

From the 1860s onward, Wilhelm Wundt (the eventual founder of so-called "physiological" laboratory psychology), would attempt to draw the associationist and psychophysical themes together. In doing so he produced the initial formulation of what would become the "discipline" of psychological science. There were, however, certain built-in constrictive limitations contained within Wundt's methodological assumptions and empirical methods (e.g., the goals, style, and intended content of his "experimental" practice), which even his own students would rebel against. In this regard, we should be careful to mention upfront that all of the philosophical and empirical inquiries to be covered in this Section (up to and including those of Wundt) take place within a pre-evolutionary intellectual context which later psychological science would have to surmount.

British Associationism

We have already encountered early appeals to associationist principles in the positions of Locke (1690) who mentions associations between ideas; as well as in Berkeley (1710) and Hume (1739; 1748) who emphasize associations between sensations. Further, with Kant (1781) we encountered a rationalist (rather than empiricist) form of associationism which he conceived as an interaction between sensation and a priori categories of the mind.

The subsequent figures who (in the mid-18th through early 19th century) further elaborated this implied association theory as an explicit psychology, were called "associationists." They were almost exclusively British (including David Hartley, Thomas Brown, James Mill, John Stuart Mill), and as a school are therefore referred to as the British associationists.

The British associationists will be concerned with bridging the gap between the real and perceived world which was the "tension of the time" left to it by Hume and Kant. These efforts, which took place in the definitively pre-evolutionary era (up to 1859), were based predominantly upon varied sorts of mechanical-atomistic thinking passed down from Hobbes and Newton. Further, all of the various permutations of British associationism ended up proposing one form or another of psycho-physical parallelism and we will want to become clear as to why this was so.

Under the earlier and informal philosophical forms of perceptual associationism, there was always an implied assumption of atomism. Berkeley and even Locke, for instance, had argued that we take all the sensory elements as presented, somehow combine these, and that is how one gains an appreciation of objects in the world. Although the various associationist figures covered below each produce their own particular account of how such associations come about and also put forward specific "psychological" theories regarding the relationship between so-called simple and complex ideas accordingly, the basic methodological assumptions of atomism remain largely unchanged throughout.

The British associationists claimed that association is a basic explanatory principle which can account for mentality, so we will want to consider the varied methodological starting-points, the methods of inquiry utilized, and the eventual endpoint of their particular positions in some detail. From a commonsense point of view, one can most certainly talk about associations between things as occurring in our daily life. One might read something in a book, or see something either on television or more directly during your daily routine, which reminds you of a whole lot of other things. Poetry, musical lyrics, and even instrumental mood music, for instance, all work on that premise. Similarly, commercial advertisements associate their products with concepts like happiness, success, and prestige. So, association of some sort certainly does occur on a daily basis. The main question at issue here, however, is whether association principles of the sort proposed by these figures will account for everything which is going on in the mind.

The first of these figures is David Hartley (1705-1757), an English physician and philosopher who attempted to extend Newton's physics into a methodologically materialist psychology of association between ideas. His Observations on Man (Vol. 1 & 2, 1749) was a wide-ranging synthesis of the neurology, moral philosophy, and spirituality of the era.

Hartley's (1749) work is most notable to us for its advocacy of an explicitly stated psycho-physical parallelism. Being more of a Lockean than a Humean, Hartley granted the existence of physical objects. He was an indirect realist of the objective idealist stripe. Being also an atomist, however, he conceived of the physical world as a system of "vibrations," an idea he got from Newton and Galileo.

These physical vibrations in the world, he suggested, caused sympathetic movements in the brain called "vibratiuncules". What is interesting about this theory is that both the worldly vibrations and the cranial "vibratiuncules" were considered as strictly physical phenomena, which ran in "parallel" with the sensations and ideas without directly causing them. Hartley considers them as the original material substrate for later mental activity.

Heidbreder (1933) indicates that Hartley's principle of mental association is a fairly standard and familiar one:

There were, thus, two "classes" of associational laws to account for: One for sensation making ideas (mental association); and the other for vibrations getting together to form "vibratiuncules" (physical association -a.k.a., the "doctrine of vibrations"). Both classes took place on the basis of contiguity and repetition but Hartley postulated a differential role for each in the production of "original automatic" versus subsequent forms of "voluntary" or "secondarily automatic actions of the body."

The key to understanding his adoption of this psycho-physical parallelism is to recognize that Hartley's goal is to distinguish between originally "automatic" action (later called bodily reflex) and the subsequent development of both learned "voluntary" action and what can be called second order automatic operations ("secondarily automatic actions of the body").

Utilizing the examples of both the development of speech (Prop. 21) and of walking (Prop. 77) in an infant, Hartley elaborates his scheme as follows:

In addition to the "commonsense" approach of Locke and in severe contrast to the "logical" or "professorial" approaches of Hume and Kant respectively, Hartley brought with him the empirical observational skills of a physician. The result is a the first thoroughgoing application of materialist plus associationist principles to topics which border on the kind of developmental observations which would be carried out routinely in the following century.

Despite occasional discursive overstatements, Hartley is someone who has turned to the developmental aspects of the Lockean issue of simple and complex ideas. He attempts to use both material and mental concepts to understand their development. Further, there is a notable aspect of historical self-awareness in Hartley's writings because he recognizes that the particular analytical concepts he is using may very well prove "fictitious" in the long run.

After Thomas Reid and Dugald Steward, Thomas Brown can be considered the third member of the Scottish Realist School of Common Sense. Having studied both law and medicine at the University of Edinburgh, Brown produced An Inquiry into the Relation of Cause and Effect (1804) and was appointed professor of Moral Philosophy there in 1810 but died of exhaustion by 1820. His chief work, Lectures on the Philosophy of the Human Mind was published posthumously that year (see also T. Dixon, (Ed.)., Life and Collected Works of Thomas Brown, 2003).

Brown, Stewart, and the Scottish School, attempted to counter the growing skepticism about reality and religion as generated by Hume. Brown’s ambivalent attitude towards the teachings of Reid and Stewart, however, is apparent throughout his Lectures (1820). That work is most notable to us for three things: A theory of "muscle sense" as providing both a means by which reality is know and a principle which unifies the mind; his choice of the term "suggestion" rather than association in order to emphasize the active selective aspects of mind; and his rejection of "nominalism" (later called the naming fallacy).

In his analysis of the processes of sensation, Brown attaches great importance to muscular sense as the basis for "objective reference" (Brown, 1820, Vol. 2, Lect. 25). Physiologists had recently begun to realize that tactile sensory impulses arise, not only from the outside world, but also from the interior of the trunk and limbs, and that these impulses are important in forming an understanding of the general attitude of our bodies as well as in the development of coordinated movements.

It was here that Brown provided a constructive critique of Thomas Reid's (1785) discursive distinction between sensation and perception. Reid had suggested a working distinction between sensation (being the simple "feeling" that immediately follows the action of an external object on any of our organs) and perception (being the "attribution" of this feeling to the external body as its cause) as follows:

Brown (1820) attempts to close the argumentative gap apparently left open in Reid's above account by way of emphasizing that it is not merely the smell but the "handling" of the rose (the muscular feedback it provides) which allows us to directly attribute the smell of the rose to a real object. In other words, in opposition to the skeptics, Brown held that our belief in the existence of reality was based on muscular activity -i.e., due to the sensations resulting from palpable manipulation of and bodily effort toward objects (Stagner, 1988). This, of course, is more of a corrective clarification rather than a counter-argument to Reid's direct realism which Thomas Brown shared.

A second important aspect of Brown's (1820) account is that he had specific and explicit theoretical differences with the traditional account of "association" provided by both Hartley (1749) and the older British empiricists. While not completely abandoning the term "association," he tended to favor the term "suggestion" to demarcate his departure from the former physiologically reductive and mental mechanistic aspects of those positions.

In enunciating his two principles of mental life -which he called "simple suggestion" and "relative" suggestion- Brown was attempting to remedy some of the main deficiencies of former association psychology. His was trying to make it more useful and self-consistent than it had formerly been.

Brown's primary ("simple") laws of suggestion are roughly equivalent to those proposed by "associationism" proper including contiguity, resemblance, and recency. He points out, however, that even these primary laws do not derive "solely" from either mental or bodily-animal sources (the argumentative weakness of Hume and Hartley respectively) but from both. In other words, he is striving for a monistic account of bodily constitution and intellectual aspects which was formally lacking.

Further, Brown's account of "relative suggestion" (the power to see relations among thoughts or objects) goes well beyond the bounds of former accounts because it attempts to show in detail why associations take a particular path (or course) in any given case. As Flugel & West (1964) put it in their account of Brown: "This ability to see relations has been a regular will-o'-the-wisp in modern psychology. It has constantly been lost to sight, forgotten or neglected, and as constantly rediscovered" (p. 21).

Brown's secondary laws of suggestion include: constitutional differences of mind or temperament; differing circumstances of the moment; state of health or efficiency of the body; and prior habits. They are explicitly intended to modify the primary (abstractly stated, decontexualized) laws according to the prevailing concrete conditions of existence and thereby explain why "at this particular time and place, the thought of 'cold' brought forth 'dark' rather than 'hot'; why the image of 'butterfly' sometimes produced 'bird' and other times 'moth'" (after Watson & Evans, 1991).

It is as follows that Brown abjures from both the mechanistic mentalism of the older empiricism as well as the potentially physiological reductive implications of Hartley's (1749) account:

Various reviewers of Brown's early 19th century observational-philosophical approach to "suggestion" have either introduced or concluded their coverage by drawing analogies to later efforts along the empirical-associationist line. Thus one reviewer claims that: No psychologists actually tried to study these "laws" experimentally for about another century but when they did, the variables were very like those that Brown listed. Another that: Similar laws would be mobilized by associationistic psychologists (particularly the behaviorists) to account for the strength of conditioning. And likewise, another that: Contemporary laws, similar to those of Thomas Brown, are also found in the learning theory of Clark L. Hull, in his book, Principles of Behavior (1943).

We should be careful, however, to take note of the third important aspect of Brown's (1820) argument -i.e., the one concerning "nominalism" (later called the naming fallacy, or more specifically the psychologist's fallacy). Brown was so concerned with getting his terminology right that he took issue with Reid over even the most finite points of psychological subject matter. He complained, for instance, that Reid's account of consciousness was written out as if consciousness existed as something separate from the contents of the mind. Stagner (1988) summarizes this point quite nicely:

In other words, just as Brown was so very careful to differentiate his position from those of even his closest and intellectually amiable contemporaries, so we should likewise be doubly careful to note the divergence as well as the overlap between Brown's attempt at concrete description of "suggestion" and the later methodology of quantitatively defined "association variables" used in 20th century "learning" theories (see Section 5). The oft repeated, supposed analogy of approach may turn out to be wildly overgeneralized indeed.

Mill (the senior) was a Scottish born British philosopher, economist, historian, and progressive "Utilitarian" social theorist. Originally educated as a clergyman at Edinburgh, Mill gave up the ministry and went to London in 1802 to pursue a career writing for and editing periodicals. Under the influence of his friend Jeremy Benthem (who popularized the slogan "the greatest good for the greatest number"), Mill adopted Utilitarianism -which argues that political theory should be based upon a sound understanding of "human nature." This in turn led him toward a consideration of psychological matters in the associationist manner of the era.

Mill's main work on associationist epistemology, Analysis of the Phenomenon of the Human Mind (Vol. 1 & 2, 1829), advocated a form of mental mechanics which he called "mental physics." It was heavily influenced not only by Hobbes, Locke, Hume, and Hartley whose theory of association he applied and elaborated further; but also by the French Materialist writers.

The physics of the era was still very mechanistic and additive rather than truly dynamic or developmental. Although motion and change in the universe were now take to be an established and measurable fact, its fundamental material constituents (the elements) continued to be conceived of as essentially static entities. Let's recall here that the universal laws of mechanical motion (proposed by Newton back in 1686) dealt merely with what Aristotle once called "efficient" causation. They were descriptions of the effect or lack of an effect of some external material force on a given physical object. Right up to Mill's time, the undeniable motion of physical objects and the observable changes in not only heavenly but also organic (living) bodies was still taken to arise from merely external material-mechanical sources and any appeal to "final" causality -i.e., to the ends or directional outcome of a given dynamic event or developmental process- was still viewed as unscientific or even teleological (in the religious and mystical sense of that term).

Accordingly, Mill's "mental physics" account of human mentality retains a strict adherence to the kind of passive-mechanical atomism (a.k.a., reductive mental mechanics) which the medically trained Thomas Brown, for instance, had explicitly attempted to overcome. As Heidbreder wrote: "James Mill is sometimes cited as the associationist par excellence, for in his writings the associationistic principles were applied with such thoroughness and in such detail that their limitations became apparent along with their possibilities" (1933, p. 55). More specifically, the two main "limitations" of James Mill's (1829) account of mental physics can be considered as the necessary respective consequences of: (i) his return to the Lockean representationalist theory of perception; and (ii) his a reliance upon a strictly "additive principle" to account for the relationship between simple and complex ideas.

With regard to the first limitation, Mill's (1829) account of the "order" of associated ideas does not carry forward either Reid's (1785) or Brown's (1820) "direct realist" approach to perception, but instead relies upon a full-scale return to a Lockean (1690) indirect realist "copy" theory of perception outlined as follows:

As a consequence, the passive aspect of Locke's perception theory is carried forward into Mill's description of the origin of the strength of associations. As one reviewer declared: "Nothing is left of Brown's [active] secondary laws but frequency and vividness" (Diamond, 1974, p. 292).

Mill clearly viewed the mind as passive with the laws of frequency and vividness determining the formation of associations accordingly. Mill's violin or keyboard player (described above) reduces down to a mere mechanical receptacle or conduit for frequently repeated and vivid occurrences which 'happen to' rather than which are carried out by 'it.' This is surely a passive mechanism par excellence!

The human mind is portrayed here as a passive accrual of associations rather than an active creative function (as implied by Kant and -for different reasons- by Brown). If this be so, one might ask why so many music students give up their lessons or remain mere amateurs while so very few go on to become virtuosos? James Mill's passive account of association provides no answer to this question other than the rhetorically, self-evident, tautology that practice makes perfect!

With particular regard to the second limitation of Mill's account, he likewise portrays the ontological status of "simple versus complex ideas" as being merely additive. Gone is the roughly developmental transition from "original (simple) automatic-to-"voluntary" (complex)-to similarly complex "secondarily automatic actions" described by Hartley (1749). Instead, the assumedly higher order complex forms of thought are merely described as "coalesced, compounded or composed" additive concatenations of lower forms:

To utilize the kind of apt, though counterfactual, analogy which formal logicians are so very fond of: If James Mill were a geologist, he would be implying here that all rocks on earth are either igneous or sedimentary (which are at best "conglomerate") but never metamorphic. The higher "duplexes" and "double duplexes" of Hartley [who actually called them "decomplex"] are portrayed by Mill as mere "conglomerates" of simple ideas -"without end" perhaps, but also without their own distinctive qualities.

To sum up, James Mill (1829) started out by sidestepping the direct realist account of Reid (1785) and adopted instead an explicitly indirect realist (representational) epistemology similar to that of Locke (1690). Like Hartley (and many others afterward), he also believed that the primary mode of operation of the human mind is association, but his account of the transition between simple and complex ideas falls far short of the mark intended by even Hartley's (1749) account. Similarly, in contradistinction to Brown (1820), Mill not only constricted the number of possible laws of association to two but also portrayed the process of transition between associations as passive rather than active. Some of the deficiencies of James Mill's account were overcome, however, by his son John Stuart Mill who (albeit briefly) put forward a relatively progressive distinction between mental physics and "mental chemistry."

Mill (the younger) was a social theorist, British philosopher and liberal member of Parliament from 1865 to 1868. As the son of James Mill, he was initially educated along the lines of his father's mechanical approach to associationism. John, however, suffered a nervous breakdown at age 20 which he attributed directly to his rigid education (J.S. Mill, Autobiography, 1873). He subsequently sought to emancipated himself both personally and intellectually from this influence.

His best known political work is On Liberty (1859). It argues for personal freedom because such freedom allows creative individuals to better contribute to society. Mill also suggests that since free-market capitalism tends to result in inequity and poverty, society would be better served by adopting some form of liberal socialism.

His most important work as far as psychology and science are concerned is A System of Logic (1843, up to its 8th edition in 1874). Here, Mill drew upon a direct analogy to the burgeoning discipline of chemistry to argue that mind plays an active-creative role in the formation of simple ideas; and that "complex ideas" are more than the sum of their parts because they contain properties not found in simple ideas. He emphasized his departure from his father's mechanistic mental physics by calling his approach "mental chemistry."

At this time, the discipline of chemistry was shifting away from the mere "systematic art" of classifying elements (described by Kant, 1781) toward consideration of active-creative events like chemical reactions. It was becoming clear that in the case of chemical reactions, things did not simply "add up." If you consider all the properties of hydrogen (on its own) and all the properties of oxygen (on its own), you are in no position to know about the peculiar properties of water per se. The same can be said of the reaction between sodium and chlorine to make ordinary table salt. Such chemical reactions were beginning to be recognized as creative and also directional processes. When they occur, either in nature or in the laboratory, things happen which can't be predicted by mere insular reference to the properties of the original elements. The new properties of compounds (water, salt) can not be explained away as simply the additive sum of the original properties of their elements. A chemical reaction is a metamorphic, transformative, and directional event resulting in new properties in the compound.

Having noted these advances, J.S. Mill (1843) draws a pointedly direct analogy to them while contrasting the additive, mechanical and static associationism of the past with his more active and creative mental chemistry approach. To paraphrase the extract presented below: Just as in the case of chemical reactions, something appears in the formation of "complex ideas" that is not present in the simple ideas taken "separately." Complex ideas, therefore, are not merely additive compositions of simple ideas. They may be said to "result from," or be "generated by" the simple ideas, but they do not "consist of them."

This was the first high-profile and influential step away from the former mechanistic model of associationism so it is worth dwelling on for a moment. In particular, we should note that Mill's (1843) argument contains two aspects which have been differentially taken up in subsequent history of psychology.

The first aspect, regarding part-whole relations, is the least exciting. Complex ideas are not simple additive "conglomerations" but are the products of some kind of interaction between the simple ideas which participated in their formation. The simple ideas are lost or no longer attended to in the eventual product. It was this part-whole aspect of Mill's (1843) argument that would be taken up by subsequent thinkers and mentioned in most subdisciplinary history books. E.G. Boring's (1942) account of J.S. Mill, for instance, runs as follows:

There is, however, a second, more exciting though implicit aspect contained in Mill's (1843) use of the term "generated" which should also be highlighted and drawn into our understanding of the proper methodology or methods to be used in psychology. The formation of complex ideas from simple ones is a dynamic, transformative and directional (rather than merely a passive mechanical or interactive) process which contains its own internal motion. The simple ideas are not static constituents of the mind which are forced into motion by some external event, but are rather active participants in the generation of a complex idea. This aspect of the argument, while sometimes recognized by later historical accounts was not actually put into practice during the contemporaneous psychophysical or subsequent disciplinary-building eras of psychological inquiry and we should be careful to emphasize why this was so.

Briefly stated, part of the blame lies on Mill's own doorstep. There was an unsettling and regrettable disparity between his initial use of the active (part-whole, generative) mental chemistry analogy to account for the ontological aspects of "complex ideas" (1843) and his own subsequent more epistemological "theory of the object" presented some twenty-two years later (1865). So let's consider this argumentative disparity.

In his Examination of Sir William Hamilton's Philosophy (1865), Mill took up the issue of formulating a "psychological" theory regarding our belief in the external world:

In this latter epistemological account, Mills seems to be attempting to maintain an active representationist view consistent with his earlier ontological approach and along the lines of Locke's theory of "reflection." But the static aspect of the new account can be appreciated when we recognize that in his effort to to explain how we maintain a previously "sensed" object in our consciousness, Mill (like Hume regarding "self") is seeking out something which "persists." Mill found this persistence in the "permanent" possibilities for sensation. Boring (1950) views this latter position as "modern" but he is completely wrong on that count. Mill's theory is surely a return to the ultimately phenomenalist search for an extra principle to account for the regularity of "fugitive" sensations. In this case the extra principle is not God (as in Berkeley), but the "permanent" possibility of revisiting or of expecting to experience a given set of sensations.

So, in the intervening years between his two accounts, Mill went from utilizing an initially tidy and concrete ontological analogy which emphasized the inherent activeness and albeit indirectly perceived correspondence between objects and ideas (1843), to a rather messy and abstract epistemological discussion of the "distinction" between ideas of "matter" (as "possibility of sensations") and the having of "sensations" (1865). We can look back and wonder how very much easier it would have been for Mill to have simply foregone that abstractness by adopting a direct realist account (along the lines of Reid or Brown), but that particular possibility appears to have escaped Mill altogether.

The typical historiographic procedure for dealing with this divergence between Mill's two accounts has been to pay cursory lip-service to the whole-part aspect of Mill's (1843) argument (regarding the irreducibility of the whole), -e.g., by suggesting that it was the source of Wundt's portrayal of perception "as a complex or an integration" (Boring, 1950, p. 231)- and to then acquiesce to Mill's (1865) sensationist position by advocating the use of methods which reduce the active whole down to static sensory parts anyway. Thus, instead of repudiating this later position, Boring embraces it and likens it to a forerunner of Titchener's (1909) highly elementist "context" theory in which "a potential [perceptual] context is... nothing else than a possibility of sensation or image" (p. 233). What Boring is implying here is that even though the "whole" (the "perceptual" products of the interaction between sensory or image elements) and the active aspects of perceptual processes are what we really want to understand, the de facto task of sensation psychology is to systematically rediscover and measure the relatively elementary parts in the hope of eventually putting Humpty Dumpty back together again. But as anyone who has heard the old nursery rhyme knows, this is an impossible task even for all the king's horses and all the king's men!

As outlined immediately below, the nearly hegemonic status of this supposed necessity to use element-seeking procedural methods in psychology has very deep roots going right back to the predisciplinary sensory research of Helmholtz. There are also origins in the manner in which Wundt considered J.S. Mill's (part-whole, generative) argument to apply to the circumscribed confines of his own "physiological" experimental psychology. It bears mentioning here too that Wundt was teacher to Titchener, who in turn was mentor to the young E.G. Boring in this respect. For these and other reasons, early 20th century sensation psychologists such as S.S. Stevens -who as we will see in Section 5 was influence by and exerted influence on Boring- routinely tore asunder that which was initially claimed to be the subject matter under of investigation, "active" human perception and thinking.

Müller's Vitalism, Fechner's Psychophysics, and Helmholtz on sensory elements

We now turn to a heterogeneous group of three scientific figures who are located precisely in the formative mid-through-late 19th century disciplinary gap between philosophy of mind and the established science of psychology. They were predominantly German, Continental, figures who while sensitive to the philosophical gap left to them by Kant and Hume, were also scientists seeking a scientific-empirical solution to the issues they considered as most pressing. For Johannes Müller this meant focusing on the active (a.k.a., "vital") organism, for Gustav Fechner it was "psycho-physical" relations, and for Hermann Helmholtz it was a search for the "elements" of sensation.

In this era of research, the former predominantly epistemological debates (between Hume, Berkeley, and Kant through to the two Mills) were informally bracketed (shelved if you will) in favor of more empirical or procedural concerns. The primary intellectual effort of these figures was directed toward how to carry out empirical research into the mental-physical world relation, and they un-apologetically utilize the methods of physiology, mathematics, and the physical sciences to investigate questions regarding life-processes; organizational or active aspects of the perceptual apparatus; and its material basis accordingly.

We can look back upon the collective works of these three figures and observe that their methodological decisions (their weighing of one assumption versus another) were guided more considerably by the question of how to conduct physiological or psycho-physical research rather than by the former philosophical (ontological or epistemological) concerns of their intellectual predecessors. The main strength of their work is that they each (to varying degrees) take up one or another aspect of new advancements in early 19th century science. Their shared limitation is that they are all proposing, either temporally or intellectually speaking, pre-evolutionary approaches to the empirical investigation of mentality. Further, the respective strengths and weaknesses of their work became the very starting point for Wundt's initial methodological propositions regarding the scope and methods of his laboratory based "physiological" psychology, so we will want to review the relevant details in that regard.

Müller was a German experimental physiologist. As the first "Professor of Physiology" at the University of Berlin, he not only carried out laboratory research but also attempted to draw together the empirical and theoretical advances made in the life sciences to date. His major work Handbuch der Physiologie des Menschen [Handbook of Physiology of Humans] (Vol. 1 & 2, 1834–40), was translated as Elements of Physiology (1843).

The particularities of that work include: Müller's "Vitalism" (a pre-evolutionary anti-reductive corrective to the new rise of mechanistic assumptions); its elaboration on the "Doctrine of the Specific energies of Nerves" (originally proposed by him in 1826); and its representationalism which acted as an unfortunate foil to his otherwise progressive physiological account.

With regard to understanding Müller's advocacy of vitalism (a life force which accompanies the material aspects of physiology) we should note the "empirical and theoretical" aspects of the pre-evolutionary intellectual context in which it was proposed.

First of all, the "empirical" (observational-experimental) aspects of physiological research had been accruing steadily since the time of Descartes (1662) and the later French materialists (La Mettrie, 1748; Cabanis, 1795). As indicated in the above "Chronology of Reflex Action" (from Fearing, 1964), Müller was one among many 18th-19th century figures to have tackled the issue of mechanical versus human existence. Between Descartes and Hartley, for instance, 18 figures are listed; with 20 more up to Müller; and a further 17 up to the time of Wundt.

Secondly, physiological "theory" regarding the active organism had also progressed, but only somewhat. By Müller's time, for instance, it was considered rather passé to attempt to avoid reductive mechanism (of the Hobbesian sort) by way of appeal to "the immaterial soul" as in Descartes' interactive dualism. Similarly, although it was still acceptable to adopt either the seemingly contradictory "self-winding machines" argument of La Mettrie (1748); or even the explicitly agnostic "psycho-physical parallelism" argument (a la Hartley, 1749) -for each would allow empirical research to continue- it seemed far easier to many of the younger early 19th century researchers to just assume a "materialist" harmony and reciprocal organization of parts stance (after the manner of J.C. Reil, 1795). This situation, however, was bothersome to Müller's systematic mind and he set out on various occasions to advocate the virtues of a "vitalist" alternative.

Müller recognized that contemporary empirical advances in the biological and physiological sciences were bumping up against the boundaries of typical mechanistic-materialist theoretical doctrines regarding the primary questions of life: "What distinguishes a living organism?" "How does the mentality of animals differ from that of human beings?" "How do higher voluntary actions differ from lower reflexive ones?" Simply shelving the metaphysical aspects of these inquiries in favor of carrying out research would not, in the long run, be the best course for the new discipline of "physiology" to take because these larger issues guide the structure of (and conclusions drawn from) that research.

More specifically, Müller's, motive for his 1830s-40s appeals to some -as yet unexplained- "vital" principle was that he recognized the nervous system was in some respect prepared to meet the world. Human beings are not simply lumps of inert matter waiting for something to come along and physically shove them into motion, nor are they machines which require energy to be injected from an external source, but are "active living substance." Similarly, the perceptual apparatus used during such active life processes is itself not simply a "passive receptacle" but has its own special properties which physiology should set out to study and explain.

The point of his vitalism is that the passive mechanistic view of the living human being, and animals for that matter, was becoming increasingly inadequate in the light of what was already known about living organisms. The organization of the brain and nervous system in whole and in part had to be put there somehow and for Müller, it was the appeal to a "vital principle" which fulfilled this role albeit inadequately. Reil's (1795) strictly materialist account had also recognized the importance of observing "organizational relations between parts" but had remained mute as to the origin or importance of that organization for understanding the activeness of the whole organisms under study. So, having started out as a good Kantian, Müller rejects Reil's somewhat emergent materialist position.

To the modern post-evolutionary reader, Müller's (1843) appeal to vitalism reminds us of Anaxagoras (his principle of "nous" as a special substance that is present only in living beings). When we haven't got any other explanation of how something got there, we can always draw upon some abstract principle like 'nous,' or in this case, the 'vital' principle. It is important to note, however, that Müller's principle of vitalism was stated prior to Darwin's (1859) Origin of Species. After 1859, this kind of solution would be both unnecessary and untenable. Müller's, as it happens, was almost the last major call for a vitalistic principle. After 1859 the solution became obvious to all concerned that how this kind of organization got there was through some kind of selective evolutionary process. Only then did it became possible to account for such active life processes in an emergent materialist (rather than a mechanistic materialist) manner.

It was not at all uncommon for the senior physiological researchers of Müller's time to insist upon a "vital principle" because they could not see how such organization, which they were beginning to understand quite well, could have come about otherwise. After 1859 this sort of idea would not occur again because -whether they understood the theoretical details or not- the newer generation of practicing physiological scientists recognized that (with a general concept of evolution) we could conceivably account for how the organization got there and therefore account for life itself without any need for an extra appeal to something non-material.

The next major point regarding Müller's (1834-40) account, is to understand how his adoption of representationalism undermined the potential explanatory impact of his major life contribution to physiology "the Doctrine of the Specific energy of nerves." What we have in Müller is a correct account of what nerves do, which is embedded within an incorrect and counterproductive indirect theory of perception.

Against the older (mystical-theological) "incorporeal copy" theory of the nerves (a la Descartes, 1662) -which portrays them as passive, indiscriminate conduits through which immaterial copies (a.k.a., images) of objects pass into the soul,- Müller proposed a relatively more ontologically materialist, active, and selective alternative. This specific energy of nerves doctrine (as he called it) states simply that: Stimulation of a given nerve produces only one form of sensation regardless of how it is stimulated. Under conditions of natural (everyday) stimulation, each of the five sensory modalities is "specific" in that each is responsive to its own kind of stimulation. Further, under the exceptional conditions of illness, injury, or artificial electrical stimulation the resulting experience is specific to the nerve which is stimulated.

We should note here that Müller's role in proposing and elaborating the doctrine (1826 and 1843 respectively) was one of drawing together the results of a long chain of basic neurological observations under a single label. The examples he uses reflect the empirical gains and past efforts of many other figures. With regard to the optic nerve: electrical stimulation; pressing the eyes mechanically in the dark; and blows to the head all stimulate experience of light. Likewise, the auditory nerve will conduct only one kind of energy (sound energy) and it doesn't matter how it is stimulated that's what is produced. Humming of the ears, for instance, is produced when the ear becomes infected as well as under conditions of electrical stimulation to the auditory nerve in the laboratory. In other words, Müller's doctrine argues that "copies of objects" per se do not enter (passively or otherwise) into the mind, but rather that the nerves provide us with specific "information" about the world around us in an active and rather selective manner.

These are the fundamentally correct aspects of his "selective irritability" doctrine regarding the nerves. The actual discursive manner in which the doctrine was stated, however, was highly problematic. In short, the potential emergent materialist implications of the doctrine are completely undermined by Müller's adoption of an indirect theory of perception so we will have to cover the details of his epistemological account (as well as their immediate disciplinary aftermath) before elaborating those implications.

Müller was a representationalist but he wasn't alone in adopting this position. We don't, in fact, find anyone overcoming this aspect of his work for some time to come; even Darwin doesn't do that. More immediately, this indirect theory is a common theoretical problem for all three of the main transitional 19th century figures we are currently considering (Müller, Fechner, and Helmholtz). Being representationalists they are unable to bridge that gap between the thing-as-known and the thing-in-itself. But from a scientific psychological point of view bridging this gap is quite important. All three of these figures intuit that the gap is both bridged in actual life and thus potentially bridgeable in theory. The old "being versus discourse" dialectic was recognized but despite their successive efforts to do so, none of them found the way. Understanding the details of Müller vs. Fechner, vs. Helmholtz in this respect will therefore be highly instructive.

With regard to Müller's particular approach to perception what interests us most is that although the three functional stages he postulates are an active version of Locke's methodologically materialist (outside inward) account, the crucial structural aspect (the assumed a priori status of the nervous system) is rather Kantian because it is through the nerves that the mind is prepared to meet the world as it were.

First of all with regard to the functional aspects, Müller portrayed perception as a physiological version of Locke's three stage theory. The names for his three stages (as depicted below) are identified a little differently but their general functional relationship (from outside inward) conforms to that of Locke:

Secondly, however, we have already seen (in Section 2) that the old Lockean empiricism does not stand up very well on its own. This was what Berkeley and particularly Hume had pointed out to us. Kant then came along to "save empirical science" from skepticism by postulating rational "categories" of understanding because without some sort of fundamental reciprocity between mind and world we can not account for the order and necessity of our experience. Kant, therefore, attempted to account for such order by showing how perceptual order is impressed upon worldly experience by the a priori categories of understanding.

For Kant such order and necessity comes from inside the mind. Similarly, Müller's account of the structural aspects of perception, fit right in here with the Kantian view because his order and necessity are also going to come from inside: They are going to be "given" by the nerves. From a structural perspective, then, Müller's doctrine of specific energy of nerves will be a physiological or anatomical equivalent of the sort of thing that Kant was taking about. As R.I. Watson (1979) pointed out: "Müller saw his doctrine as supporting the nativistic views of Kant about that which we perceive. After all, what is more innate than the nervous system itself?" (p. 104).

Without the aid of evolutionary theory to back him up, Müller ran into considerable difficulties while walking the fine line between Lockean and Kantian accounts. Note, for instance, that according to the above diagram the nerves are portrayed as material "intermediaries" between perceived objects and the mind (Sensorium). Further, according to Müller, it is this very "materiality" of the nerves which guarantees the functional reciprocity between the "Sensorium" and external material nature. This is the strongest aspect of Müller's epistemological position and the modern reader might be tempted to assume therefore that he would simply adopt an explicit direct realism (along the lines of Reid or Brown); but not so in the case of Müller!

Unfortunately, his actual epistemological account of what is immediately perceived does not name objects but rather the "conditions of the nerves." Through Müller's embedding of the specific energy of nerves inside an indirect realist account, he initially asserts what can be read as a typically representationalist conclusion; the denial of direct contact with "external bodies" as follows:

According to him, what we are "immediately" perceiving is not the world per se but "certain qualities or conditions" of our nerves. Well, Socrates said, "Know thyself," but he didn't know that he was talking about the nerves!

Müller, however, later clarifies this seemingly solipsistic basic position and attempts to reassert our contact with the world by way of calling attention to the "materiality" of the nerves:

Müller's argument is that because the nervous system itself is "material," it provides us with a way of contacting the matter 'out there.' In his terms, the nerves are giving us "information" about "external bodies." Again, there is an element of truth to Müller's appeal to the materiality of nerves as guaranteeing reciprocity between the perceiver and the world, which I don't think anyone (especially Müller) would wish to deny. That is, when we come into the world, we are born with a particular kind of nervous system that does prepare us to receive the world in a particular way.

The question at issue, however, is whether such a nervous system allows us to perceive the world per se or simply allows us to construct the world in our own heads. By adopting an indirect realist position to epistemology, Müller was initially forced into discursive language which implies the latter position. Müller's theory of perception is Kantian in that we only have direct access to the phenomena of the nerves. It is also as indirect as that of Locke's appeal to "experience", or Hume's appeal to "sensual image plus habit", and therefore runs into the same logical reductio.

In the final analysis, Müller becomes rather desperate to make that connection to the world, because he knows that if there is no such connection, the whole science of physiology goes out the window. Being couched within representationalism, however, his argument is circular, self-contradictory and dogmatic. If we adhere strictly to the logic of his epistemology all we can really know is the particularities of Müller's own nerves. So his adoption of an indirect realism augmented by an appeal to the materiality of the nerves doesn't work. It is still left with the tension between the real and perceived world handed down to physiology by Hume and Kant.

Müller doesn't solve the problem of knowledge but at least he made an attempt. Müller's particular contributions to later disciplinary developments include his anti-mechanistic position regarding physiology; his account of the selective irritability of the nerves; and his day to day professorial role in teaching laboratory skills to a new generation of researchers (such as Th. Schwann, R. Virchow, Helmholtz, and Emil DuBois-Raymond) who would in turn became notable founding figures in "neuropsychology."

Finally, it should be noted that although Müller seems to have implicitly favored the nerves as the "seat" of the selectivity of sensation, he was also careful enough to defer explicit judgment on that issue for it would have gone beyond the available contemporary evidence. Subsequent modern research would show that it is not the properties of the nerves themselves per se but rather their normal functional relationship with the particular brain centers at which they terminate that is the decisive source of their specificity. In other words, peripheral and central nerves can now be transplanted in lower animals and they function relatively normally in their new location.

To sum up our coverage of Müller: While his twin doctrines of vitalism and the specific energy of nerves did much to focus the research interests of most physiologists on an active organism; his adoption of an indirect realist theory of perception did much to focus others' attention away from appeal to objects and toward the mathematical measurement of so-called psycho-physical (Weber-Fechner) or sensory (Helmholtz) elements. Notice that the problem which Kant had drawn our attention to was the problem of sensation. Müller tried to provide an approach which would bridge the gap between the organism and the world but failed.

In the aftermath of Müller, Fechner's "psycho-physics" will make a similar attempt, while Helmholtz (in contradistinction to both attempts) believed more modestly that if we could just find a way to measure sensation better, perhaps these metaphysical issues would work themselves out eventually. But before moving on to Helmholtz, we should first give some account of the advancement of so-called psychophysics by mentioning the positions of Weber and Fechner.

Born in Wittemburg, Germany, the third of 13 children, Weber received his doctorate in physiology from the University of Leipzig in 1815. He began teaching there immediately after graduation and continued until retiring in 1871.

Weber was a fairly inauspicious gentleman who began his career by carrying out basic physiological research measuring the smallest "noticeable distance" between two points for touch sensation on various parts of the body. Later, however, he carried out research regarding the somewhat more complicated issue of "sense discriminations" (judgments) of weight; successively presented line lengths; and illumination. While these findings were all reported by him in a Latin language booklet (1834), it was not until his Handworterbuck der Physiologie [Handbook of Physiology] (1846) that they attracted much attention. Further, Weber's main importance for us is that the more complicated aspects of his research helped set the stage for Gustuv Fechner (1860) to officially launch the new field of "psycho-physics."

Regarding the simplest aspects of his cutaneous (skin) sensation research, Weber used the dulled points of a standard compass to find that the "two-point threshold" on the skin varied with the body part investigated. The threshold for the tip of the tongue (1 mm), for instance, was found to be more than fifty times as precise as that of the upper arm or thigh; and similarly, that the back had the largest two-point threshold (60 mm). Later, he explained these results by suggesting that the skin is divided into areas ("sensory circles") with the respective sensitivity of any specific area corresponding directly to the relative distribution of the nerve endings in that area (1852).

Regarding the more complicated, seminal, aspects of his research, Weber (1834) also reported carrying out "just noticeable differences" (JND) research for judgments of weights under two conditions. In the first condition, weights passively rested on the hand of a subject. In the second condition, the weights were actively handled by the subject. Two important discoveries were forthcoming: (1) that active perception is finer than passive perception; and (2) that the JND in both conditions was always a "constant fraction" of the basic noticeable increment of weight involved.

To elaborate on the first discovery, Weber wanted to know "how much heavier" does the second weight have to be before it is judged to be different from the first. Under the condition of passive judgments, where the weight is simply placed on the subject's hand, the difference has to be fairly large (1 part in 30). But under conditions of active discrimination, where the weights are picked up by the subject, the required difference is considerably smaller (1 part in 40). We gain more discriminating information from our active perceptual activity. This was the first empirically measured indication that such active perceptual discrimination is important.

To elaborate on the second discovery, each subsequent detectable increase in weight sensation occurs only when the basic incremental difference for that modality has been surpassed. Double the weight, double the required increment of increase in weight; half the weight, halve the required increment. For instance, in the second active condition of weight discrimination, if you are holding a 40 pound weight in one hand, you will be able to recognize that a 41 pound weight in the other hand is in fact different by hefting it upward. But if the first weight is 20 pounds, you could detect a mere half pound difference. In other words, with regard to active weight discriminations, we can recognize a 1/40 difference, whatever the particular weights involved are. Weber's point was that the same relative "ratio" is "constant" across comparisons of the same kind.

Further, Weber presented empirical evidence that this observational regularity was not just peculiar to weight judgments but also generalized to visual judgments regarding lines presented successively; as well to judgments of luminosity; and he further stipulated that it might also apply to other senses like sound too.

Weber (1835) suggests the perceived difference between the two experimentally presented sensory stimuli is dependent not upon the "absolute" size of the difference but upon the "relative" ratio of difference of the "constant standard" for that particular sensory modality (e.g., 1/40 for active weight discriminations; 1/10 for illumination, and 1/100 for visual line judgments).

This empirical regularity was later labeled by Fechner (1860) as "Weber’s law" or the Weber "fraction" and was given a formal generalized mathematical expression as follows: dR /R = k, which means simply that the proportion of the minimum detectable change (dR) to the strength (size) of the stimulus (R) is a constant (k) across varying levels of intensity (with R standing for "Reiz" in German, meaning stimulus). What is constant is the ratio between the basic stimulus size (e.g., weight, line length, or luminosity) and the extra amount required to bring a discrimination of change about.

In anticipating later refinements, we should mention here that although this "constant" ratio holds true for a wide range of medium intensities it was eventually found to break down for very low and for very high intensities. So, today's psychophysicists have much more complicated formulas to account for these extreme conditions.

Even though Weber considered his observational generalization as important as any other empirical physiological regularity, he did not consider it as having any far reaching philosophical significance. Gustav Fechner, however, places it in the very center of a new psychological movement:

After receiving an MD in 1822 at the University of Leipzig, where Weber had been teaching physiology since 1815, young Fechner initially failed to receive any official position in physiology and made ends meet by translating various physics textbooks (from French to German). This, in turn, led to a teaching position in physics at Leipzig from 1824-1839. At that point, however, he fell into 11 years of depression until October of 1850 when he believed he had found a "psycho-physical" basis for a spiritualist philosophy of science.

During this middle depressive period, in which he was wrestling with the problem which Kant had left us (the supposed disconnect between the perceiver and the world), Fechner was initially influenced by Schelling who considered philosophy as the science of the absolute in its double manifestation: nature and mind. Fechner was then rather profoundly influenced by Weber's (1846) modest summary of his basically empirical work -especially the mathematical constant which Fechner now labeled "Weber's Law."

Fechner suggested that the true significance of this empirical law lay not in its mere empirical-descriptive aspects but in the methodological realm. For according to him, it revealed a long sought after connection between the physical and the psychical. Fechner's Elements of Psychophysics (1860) was the culminative summary of his own work during this period, and while it did not immediately (or even ultimately) "turn the world's ear" toward his philosophical view, it did spur others including Helmholtz, Volkmann, and then S.S. Stevens onto their elaborations of psychophysical measurement.

Fechner's major preoccupation during his personal depressive phase was with finding a way to establish a relationship between the seemingly separate physical-scientific and the spiritual-ethical world views. Here he was influenced by Schelling (1775-1854) who, like Fichte, was part of that whole turn of events in philosophy which followed from Kant's supposedly unresolvable antinomies. Schelling and Fichte rejected Kant's convenient appeal to merely logical antinomies and pointed out that in "practical" terms all philosophers and scientists are required to abide by the "theoretical imperative" -they must take a stand on controversial issues instead of just living with them as ultimately unresolvable quandaries. In considering this post-Kantian period of philosophy Ilyenkov (1977) encapsulates it into what he calls the "monistic strivings" of the times. This was a period in which figures like Schelling and Fichte are attempting to work out a "unitary conception" of the world which overcomes the logical quandaries of the past:

With regard to how these "monistic strivings" were picked up by Fechner as a basis for scientific psychophysical investigations, we can not do better than to turn directly to Edna Heidbreder's masterful account:

We should note that Heidbreder's use of terms like "victory, rival claims, values, and unity" are not accidental. They reflect the continuing disciplinary situation which Fechner was facing and attempting to surmount. She also does a very good job of relating Fechner's enthusiasm and genuine concern on issues which concern us all, including the issue of the possibility of psychology "as a science." Kant (1781), in particular, had claimed that psychology could never become a science because mind could not be subjected to "mathematical or experimental" methods of investigation. The activities and the contents of the mind could not be "measured," and therefore an objectivity such as that achieved in physics and chemistry was out of reach. Psychology would forever remain subjective. Fechner's (1860) counter-argument was that since psychological events are in fact tied to measurable physical events in a systematic and predictable way, psychology could be a science after all!

The specific means of Fechner's solution was to convert "Weber's constant" into an equation which is now known as the Weber-Fechner law (S = k log R) -with sensation on one side and stimulus on the other. More specifically, S and R stand for German words, where S is sensation (not stimulus) and R is "rinem," stimulus (not response). Thus, reasoned Fechner, any given sensation could be predicted as equivalent to the constant (k, or the Weber fraction determined empirically for that sense modality), times the logarithm of the particular stimulus in question. The equation, Sensation=k log R(Stimulus), says literally that the strength of a mental sensation equals a constant logarithmic (mathematical) function of the strength of the stimulus. In other words, it says that as the discriminated 'mental series' increases arithmetically, the 'stimulus series' must increase geometrically.

The important thing for us, however, is not to get bogged down in these specific details, but to recognize that this formula was intended by Fechner as a "mathematical bridge" between the object (stimulus) on the one side and the perceived sensation on the other. He believed he had thereby overcome the Kantian epistemological object-subject dualism. What he actually did, however, is replace it with a psychophysical version of double-aspect theory in which the strength of unobservable mental events would be physicalized operationally by way of mathematics. This is a description of, and means of predicting, the strength of the resulting isolated sensations arising from a given laboratory situation, but it is hardly an explanatory account of the nature of those sensations as they occur to or function within the perceiving organism. Fechner's equation simply defines the "sensation end" of the formula in terms of the "stimulus end." It does not state the practical, developmental, or organismic relations between them.

As in the case of Müller, what we can appreciate most about Fechner is his recognition of and motivation to find a solution for the methodological (subject-object) problem, but we must also acknowledge that given the pre-evolutionary context of his thought, he was unable to resolve it sufficiently. Subsequent workers in psychophysics (including Helmholtz) would consequently abandon Fechner's wider "metaphysical" concerns and concentrate instead on the more myopic pursuits of measuring what they could.

The mathematical-measurement side of Fechner's efforts (the belief that one can measure specific psychological characteristics albeit indirectly and perhaps learn something about them) can be said to have helped stimulate subsequent experimental psychology and individual differences research. I suppose, however, that it is just as apt to close our coverage of Fechner by mentioning that this was just the sort of empirical-experimental psychology which the quintessential late 19th century evolutionary thinker William James (1890; 1892) found so very sterile and dull (see Section 4).

Born in Potsdam (near Berlin) to parents of modest teaching and military backgrounds, young Hermann showed early promise in physics, but was trained as a surgeon at the Berlin Institute in exchange for service to the Prussian Army. During this period of training (1838-1842) Helmholtz studied physiology under Johannes Müller (then at the height of his institutional power), and actively mixed with Müller's University of Berlin students. It was at this time that Helmholtz established long-lasting relationships with DuBois-Raymond, Virchow and Ludwig who all swore to reject vitalism.

While serving out his military obligation in Potsdam, Helmholtz set up a makeshift physiological laboratory. Due to the wider import of his initial research (on metabolic processes in frogs) as well as his active discursive role (1847) in the ongoing emergence of the conservation of energy doctrine, Helmholtz was released early from Army service. Between 1849 and 1871, he went on to three professorships in physiology. At Königsberg (Kant's university) he both measured the rate of nervous impulse (in frogs and humans) and invented the ophthalmoscope (1851). At Bonn (1856-1858) he extended his interests to acoustics. During a longer stay at Heidelberg he proposed the Young-Helmholtz theory of color vision (1860) and the resonance theory of hearing (1863). In 1871, however, Helmholtz was finally appointed to the University of Berlin (in physics) where he occupied himself with the further application of the conservation law to the areas of hydrodynamics and electrodynamics.

We will consider four aspects of his approach to the physiology of the senses: (1) his rejection of vitalism in favor of a reductive experimental-materialist account of nervous impulse and sensory transduction; (2) his adoption of an indirect realist "enrichment" theory of perception -whereby undifferentiated sensory elements plus unconscious inference are said to establish contact with the world; (3) his rationale for favoring "empiricism" rather than nativism regarding perception of space; and (4) his disciplinary import for later developments including the limiting of empirical method to well-trained, immobile, adult human subjects.

James J. Gibson's (1966, 1979) direct realist "differentiation" theory of perception will also be introduced here as a basis upon which to surmount the difficulties of points 1-4 above, as well as to provide a standard by which we can then evaluate post-Helmholtzian disciplinary debates in Wundt, Külpe, and Titchener regarding the issue of higher mental processes. For to really understand Helmholtz is to understand the initial means by which active, everyday, natural observers looking around or listening to objects in the world become analytically reduced to passive, constrained, though well-trained "observers of sensory elements" (looking at, or receiving auditory stimulation from laboratory apparatus).

Back in his Berlin student days, Helmholtz entered into an antivitalist alliance called the "Physicalist Club" and promised to appeal to "No other forces than common physical-chemical ones... within the organism." This was to be a reductive "physiological" rather than a mechanical materialist position. Its aim would be to apply the "law of the conservation of energy" (i.e., that energy could be transformed from one state to another, but never created or destroyed) to "living organisms."

Similarly, in opposition to the nativist structural aspect of Müller's position on perception (which seemingly locked the organism into a loop of reference merely to its own nervous energies), Helmholtz would adopt a practically guided Lockean position which "got on with the job" of empirically investigating the senses without becoming mired in the metaphysical debates of German philosophy. As Boring (1950) points out, Helmholtz was more "British" than German in this aspect of his basic methodological assumptions. His was to be an experimental-physiological account of both the rate of nervous impulse and sensory transduction which appealed to no mysterious vital force or unknowable object.

The questions Helmholtz asked were essentially empirical: "How fast is the neural impulse of motor versus the sensory nerves?"; "By what means is physical energy from objects transduced in the senses of vision and hearing?"; and "Is perception of space learned or given to the senses innately?" With regard to the first two questions, we should note upfront that they are relatively straightforward matters of experimental evidence which Helmholtz answered very well. The latter question, however, was framed within an implicitly held enrichment theory of perception which he shared with his nativist opponents and therefore was not answered well by Helmholtz or by many others who followed.

For Helmholtz, casting off the belief in any ubiquitous non-material force led him to question Müller's unexamined position that the brain delivered willful commands to the muscles in an instantaneous unmeasurable manner. The immediate impetus for his empirical interest in this issue of nerve conduction rate was the theory of DuBois-Raymond (1845) -a fellow Physicalist Club member- who suggested that if the nervous impulse involved a physical-chemical transduction rather than an immaterial act of will, it might also take enough time to be measurable.

By 1850 Helmholtz was measuring the rate of impulse in the motor nerve of severed frog legs. This was done by setting up a laboratory galvanometer with a known rate of deflection of its needle so that it is switched-on when the nerve is stimulated and switched-off when leg contraction disconnects the circuit. Thus, deflection of the galvanic needle provided a time interval for each of the successive stimulations applied at known distances along that motor nerve. A simple mathematical computation of known distance versus known time-lapse could then be worked out to establish the average rate it took for the impulse to traverse each distance:

Finding the results fairly regular and consistent, Helmholtz estimated the overall average speed of the frog's motor nerve conduction to be about 30 meters per second. Baxt (1867) modified the procedure for human subjects estimating the rate of motor impulse at about 33 meters per second. This was done by stimulating the nerve to the ball of the thumb, either at the wrist or above the elbow (thereby producing a twitch), while the hand, forearm and elbow were held motionless in a plaster cast.

Meanwhile, back at Königsberg, Helmholtz had already moved to the more tricky task of measuring sensory nerve conduction in intact human subjects. This was done by way of stimulating the toe or thigh (respectively) and having the subjects 'report' (by pressing a telegraph key) as soon as they detected each stimulation. The results were so variable that Helmholtz declined to make any proclamation on the speed of sensory nerves. It was only later that F.C. Donders (1868), -who had initially set out in searching for a universal mathematical psychological constant similar to that of Newton's law of gravity- distinguished between simple discrimination and choice reaction times (which he found to increase in duration and variability respectively). In other words, the task of estimating sensory nerve impulse rates turned out to be far more complex than first anticipated.

Thus, aside from having obtained a positive answer to the old Kantian question regarding measurement ("Can we measure psychic events?"), the most important methodological generalization made from this Helmholtzian era research was that the merely additive model doesn't work. It was too simplistic to cover the observed irregularities of the measurements made. More complex mathematical and theoretical models of the nervous system (those beyond the scope of the contemporaneous pre-evolutionary knowledge) would be required to account for the observed empirical variability of such data.

Helmholtz, however, was content to put aside these deeper methodological considerations (for later analysis by others), and moved on instead to a closer consideration of the anatomical-physiological aspects of sensory transduction in particular. For, unlike Fechner or Donders "Helmholtz was not given to brooding about the unity of the universe. He wanted to know, among many other things, exactly how the eye and the ear worked... [So] he invented apparatus, devised experimental methods, and constructed theories [accordingly]" (Heidbreder, 1933, p. 85).

Instead of getting bogged down in metaphysics, Helmholtz held to the attitude that the more we learn about sensation the better; and, further, that perhaps by virtue of carrying out empirical research (and by proposing albeit contentually circumscribed theories), the metaphysical issues might someday resolve themselves. His two major works along this line of inquiry (Treatise on Physiological Optics, 1856-1866; and Sensations of Tone, 1863/1875), therefore, are characterized by a convenient convergence of the physiological, philosophical, and experimental traditions of empiricism as they applied specifically to the empirical aspects of sensory transduction.

While the experimental aspects of these works foreshadow the Wundtian laboratory psychology to follow, their equally prevalent reductive sensory-element aspects were then picked up by E.B. Titchener, brought over to America, and still live on in the contemporary (and highly problematic) subdiscipline called "Sensory Processes." As for the philosophical assumptions, they remained muted in Helmholtz and became unquestioned in the subsequent North American elaboration. They did not, however, go away. Nor did they resolve themselves as Helmholtz had hoped. So, we will want to understand a bit about each of these 'experimental, reductive, and philosophical' aspects as we proceed.

The primary and explicit focus of the Helmholtzian empirical research was on the distinctly physiological investigation of sensory transduction in the retina (of the eye) and in the cochlear membrane (of the ear) respectively. In part, this empirical focus was an extension of Müller's "specific energies of nerves" hypothesis to the qualities of particular sensory modalities. In other words, both his trichromatic theory of retinal transduction and his resonance theory of auditory transduction were posed as accounts of how physical energy was being transduced into the neural energy of Müller. This is all well and good (as far as it goes); and his account of such sensory transduction still holds up relatively well today.

The issue for us, however, is to recognize that in his initial attempts to apply the procedures of the physiological laboratory to psychological topics, certain problematic assumptions were imbedded in the way Helmholtz laid out the respective tasks to be addressed by the physicist, physiologist, and psychologist. Helmholtz (1866) certainly recognized that there must be a division of labor in the science of the senses and (as Brauns, 1997, points out) he laid out this division as follows:

The work of Helmholtz shines brightly with regard to the first two tasks outlined above, but it is in the definition of the latter psychological task as well as in the limitations on method imposed by that definition where the problems of his admittedly early account reside. Stated plainly, we are about to show that his definition of the psychological task starts from a rather reductive assumption that perception is built up from sensory elements and, further, that the indirect (enrichment) theory of perception which he adopts as a result of this definition imposes (in turn) unwarrantable limitations on both his account of proper experimental method and on his application of this method to specific psychological topics like space perception. We must, therefore, highlight these implied aspects of his work in a manner which Helmholtz would not have been able, or perhaps even willing, to do himself.

First off, Helmholtz takes it for granted that perception is built up from combinations of sensory elements which are concurrently supplemented with intellectual qualities (along the line of Locke's secondary qualities). Perception, he suggests, begins with simple undifferentiated sensations received rather passively through anatomical channels in the sensory apparatus of both humans and animals. But as Gibson (1966) would later point out, whenever the world is considered as not directly revealed to us but only signified indirectly through undifferentiated sensory elements, some additional intellectualizing principle is required to get out there to the external world. In order to avoid being trapped in the old philosophical 'barrier of the senses,' therefore, Helmholtz suggests that elementary sensory elements are supplemented by unconscious inferences which attribute these elements to external objects:

Note that according to Helmholtz, the "real relations" means simply that sensations and not objects are the stuff to which our perceptual apparatus (retinas, choclear membrane, etc.) refers; and that he is also implying that while this is especially true in the physiological vision laboratory, it is also true of "ordinary normal conditions" in everyday life. It is in this manner that Helmholtz presents his rather static, anatomically fixated account of perception which retains an albeit intellectually qualified indirect perception theory.

As Boring (1950) pointed out, this is an account of perception which is very similar to that of J.S. Mill's (1865) -where perception is defined as the "permanent possibilities for sensation." Having made this cogent observation, Boring promptly drops the matter (p. 313). Indeed, until relatively recently (with Gibson's respective 1966 and 1979 critiques) this sort of indirect account (that we are acquainted only with the qualities of our nerves, or neurons, or retinal locales; but not with the properties of the external world) seemed to be the unassailable basis for any physiological theory of perception.

Knowledge for Helmholtz and many others thereafter begins with uninterpreted sensory building blocks which can not be appreciated except by a special act of attention and which are typically then unconsciously and automatically supplemented by unconscious intellectual inference. After all, if we only have the anatomical deliverance of sensation to go by, we must have to somehow intellectually deduce or induce the worldly causes of these sensations, for we can not detect them directly.

As for the kind of "special acts of attention" he is referring to, Helmholtz suggests that if one is standing on a hilltop surveying a wooded landscape, the normal blending of color in green foliage and blue sky can be appreciated as being made up of fine gradations of a multitude of simpler shades if one turns one's back from that landscape and views it upside down though one's legs! Other special acts of attention can be carried out by trained laboratory observers too, and it is here that we begin to gain a better appreciation of how the assumed indirect perception theory of perception can lead (so to speak) researchers toward investigating very abstract (unnaturalistic) forms of questions through highly constrained laboratory procedures.

Just how this inferential (enrichment) theory played out in terms of defining appropriate subject matter for and methods of investigation can be shown by looking at comments made by Helmholtz on vision and methods. First of all, Helmholtz defined vision itself as "pointing the eyes" (as looking-at rather than looking-around).

According to this definition, "vision" (at best) involves eye movements relative to the head. The implication for method of study, therefore, is that the natural proclivity of a naive observer to look around must be constrained and controlled out of the laboratory setting. In such studies, the eyes of an observer would sometimes be allowed to scan a stimulus display with the "field of view" being limited to that of a stationary head which was often physically restrained by an apparatus such as a chin rest. At other times, however, the eyes of the observer would have to be held as still as possible so that the stimulus display would fall on the foveal region of the retina (on the anatomical region of maximum acuity). The sensitivity of various points on the retina to color or level of illumination could thereby be mapped.

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