feest_op in psychology

OPERATIONISM IN PSYCHOLOGY: WHAT THE DEBATE IS ABOUT, WHAT THEDEBATE SHOULD BE ABOUT*

ULJANA FEEST

I offer an analysis of operationism in psychology, which is rooted in an historical study ofthe investigative practices of two of its early proponents (S. S. Stevens and E. C. Tolman).According to this analysis, early psychological operationists emphasized the importance ofexperimental operations and called for scientists to specify what kinds of operations wereto count as empirical indicators for the referents of their concepts. While such specifica-tions were referred to as “definitions,” I show that such definitions were not taken to con-stitute a priori knowledge or be analytically true. Rather, they served the pragmatic func-tion of enabling scientists to do research on a purported phenomenon. I argue thathistorical and philosophical discussions of problems with operationism have conflated it,both conceptually and historically, with positivism, and I raise the question of what are the“real” issues behind the debate about operationism. © 2005 Wiley Periodicals, Inc.

The term operationism (or operationalism) is commonly associated with the Harvard physi-cist Percy Bridgman (1882–1961), who famously claimed that “in general, we mean by a conceptnothing more than a set of operations; the concept is synonymous with the corresponding sets ofoperations” (Bridgman, 1927, p. 5). While the notion of operationism was never very influentialwithin physics, it gained a fair amount of popularity within psychology and the social sciences(Smith, 1997, p. 668). Even today, the notion of operationism plays an important role in psychol-ogy, with many introductory textbooks on psychological methods devoting a section to opera-tionism. However, over the years there has also been a sporadic but ongoing debate about the na-ture and tenability of psychological operationism. After varieties of this position were firstformulated and elaborated on by Stevens (1935b, 1935c, 1936, 1939a) and Tolman (1936/1958f,1937, 1938/1958d), a number of papers appeared in the Psychological Review (Bergmann &Spence, 1941; Israel, 1945; Israel & Goldstein, 1944; Pennington & Finan, 1940; Waters &Pennington, 1938; Weber, 1940), critically discussing the vices and virtues of this position. Thisdebate culminated in a symposium on operationism, organized by the Psychological Review(Boring et al., 1945). A decade later, another philosophical symposium was devoted to the issue(Frank, 1956). During the same time period, the notion of operationism underwent certain modi-fications within psychology (Campbell & Fiske, 1959; Garner, Hake, & Erikson, 1956). The no-tion of operationism was once again discussed in the early 1980s (Leahey, 1980, 1981, 1983, whowas critical of the position, and Kendler, 1981, 1983, who defended it), and the early 1990s (Green,1992; Koch, 1992, both of whom were very critical of operationism). Most recently, the journalTheory and Psychology published a positive analysis of the development of operationism (Grace,2001), followed by several critical commentaries (Bickhard, 2001; Green, 2001; Rogers, 2001).

ULJANA FEEST is a research scholar at the Max Planck Institute for the History of Science in Berlin,where she works on the historical relationship between Gestalt psychology and philosophy of science, andthe epistemology of psychological experiments. She received a degree in psychology at the University ofFrankfurt (Germany), and a Ph.D. at the Department of History and Philosophy of Science, University ofPittsburgh. This paper is based on parts of her dissertation, entitled “Operationism, Experimentation,and Concept Formation” (University of Pittsburgh, 2003).

Journal of the History of the Behavioral Sciences, Vol. 41(2), 131–149 Spring 2005Published online in Wiley Interscience (www.interscience.wiley.com). DOI 10.1002 /jhbs.20079© 2005 Wiley Periodicals, Inc.

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*Editor’s Note: This article, based on a paper delivered at the annual conference of the European Society for theHistory of the Human Sciences held in York in the summer of 2003, is the winner of the ESHHS/JHBS Early CareerAward for 2003.

The disagreements between advocates and critics of operationism appear to be largely ofa philosophical nature. However, in discussing problems with operationism, proponents of thisdebate (in particular, critics of operationism) have made certain conceptual and historical as-sumptions—i.e., they have worked with particular notions of what the position of operationismstates and what its historical origins were. In this article, I want to question some of these con-ceptual and historical assumptions. To this end, I will draw on case studies of two early opera-tionists, Stanley Smith Stevens (1906–1973) and Edward Chace Tolman (1886–1959). Thesecase studies serve a dual purpose. On the one hand, I use them to provide a conceptual analy-sis of operationism, which is grounded in an analysis of the role operationism played in the ex-perimental research of some of its early proponents. On the other hand, I use them to provideevidential support for my thesis that operationism was historically not as closely tied to certainother movements (most importantly, logical positivism) as is assumed by its critics.

ANALYZING METHODOLOGY IN THE CONTEXT OF INVESTIGATIVE PRACTICE

Critics of operationism have proceeded by pointing out that operationism is fatally flawed,because it has its roots in—and/or is identical with—flawed philosophical positions (e.g., Green,1992; Leahey, 1980, 1981, 1983; Rogers, 2001), or arises from misunderstandings of such posi-tions (Green, 1992; Koch, 1992). In this article, I will focus on the assumption that operationismis an expression of a logical positivist epistemology and a verificationist theory of meaning.1 Thisassumption is clearly behind the charge that psychologists have failed to notice that neither ofthose positions is still en vogue within philosophy. Varieties of this critique have been formulatedboth by philosophers and by historians of psychology. For example, the philosopher Fred Suppewrites: “[I]t seems to be characteristic, but unfortunate, of science to continue holding philo-sophical positions, long after they are discredited” (Suppe, 1977, p. 19). In a similar vein, the his-torian Thomas Leahey states that “[p]sychologists . . . persisted (and still persist) in attempting to‘define’ each theoretical term empirically even after the positivists had given it up for cognitivelysignificant interpretive systems” (Leahey, 1980, pp. 132–133). Interestingly, however, the samehistorian also asserts that in actual scientific practice psychologists do not provide operationaldefinitions, despite their claims to the contrary. Instead, he observes that “[t]he test maker mustpersuade the psychological community that his ‘definition’ . . . is a good one. . . . We find thatoperational definitions are not analytic truths, but are subject to empirical confirmation. This sug-gests that they are not ‘definitions’ at all” (Leahey, 1980, p. 138).

However, if psychologists do not, as a matter of fact, operationally define their terms alongthe model of an outmoded philosophical theory of knowledge and meaning (and I believe thatLeahey is right about this), it is not so clear that a critique of those outmoded philosophical the-ories has much relevance to operationism as practiced by psychologists. Thus, we need an analy-sis of what the position really states, such that we can then delineate the grounds on which wewant to attack, or defend, it. In this article, I aim to provide such an analysis of operationism,grounded in analyses of the scientific contexts that first gave rise to the emergence of this con-cept. By asking what function this concept played in the investigative practices of its proponents,I follow a trend in the historiography of psychology (e.g., Danziger, 1990) that does not takemethodological writings at face value, but tries to gain an understanding of methodologies byasking how these methodologies were applied to, and emerged in the context of, specific re-

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1. Another critique has been to argue that psychologists misunderstood Bridgman (Koch, 1992). While there is somehistorical evidence that Bridgman did not play an important role in the emergence of operationism in psychology(e.g., Hardcastle, 1995), an in-depth treatment of this issue would require an analysis of Bridgman’s operationism.Such an analysis cannot be provided in this article.

search questions. Some recent commentators on operationism share this focus on investigativepractice (Rogers, 2001). However, while raising interesting questions about the emergence andlongevity of operationism (see also Rogers, 1989), this author does not offer a detailed analysisof the position itself. Instead, he criticizes defenders of operationism for believing “that grandmetatheoretic problems of the positivist project” can be solved by the introduction of a newmethod (Rogers, 2001, p. 61). The assumption here is that operationism has the very samemetatheoretic foundations (and, hence, problems) as the positivist project. It should be empha-sized that not all critics of operationism assume that it was historically closely linked to logicalpositivism. For example, Green (1992) explicitly denies this. Yet, the suggestion that psychol-ogy would be better off if operationists had taken notice of the decline of logical positivism is apervasive theme in the critical literature. I will now take a closer look at this suggestion.

TWO NOTIONS OF “OPERATIONISM”

Roughly, we can distinguish between two theses that are frequently attributed to opera-tionism, an epistemological thesis and a semantic thesis. According to the epistemological the-sis, all knowledge claims have to be reducible to actual or potential observations (see Salmon,1985). According to the semantic thesis, the meaning of a concept can be exhaustively definedby stating particular operations and their observational results. Both of these theses are com-monly associated with the philosophy of logical positivism. Therefore, I will dub this construalof operationism the “positivist” reading of operationism. In this section, I contrast this readingwith my own “methodological” reading of operationism.

Operationism: The Methodological Reading

The thesis of this section is that psychological operationism was never intended as a the-ory of meaning or a theory of knowledge in the philosophical sense. By this, I mean that psy-chologists did not intend to say, generally, what constitutes the meaning of a scientific term. Nordid they intend to provide a general account of justification for scientific knowledge. This doesnot mean that semantic and epistemological questions were of no concern. Thus, I believe thatin offering operational definitions, scientists were partially and temporarily specifying theirusage of certain concepts by saying which kinds of empirical indicators they took to be indica-tive of the referents of the concepts.2 For example, in his psychophysical work on attributes oftonal experience, the operationist Stanley Smith Stevens started with the prior assumption thatdiscriminatory behavior in response to auditory stimuli could be treated as indicative of audi-tory experience. This assumption is what was behind his “definition” of experience—i.e., that“to experience is, for the purpose of science, to react discriminatively” (Stevens, 1935c, p. 521).Given, further, a certain methodology for prompting subjects to discriminate according to par-ticular features of their auditory experience, this prior assumption enabled Stevens to do empir-ical research on the “density” and “volume” of tones and to show how each of these attributesof experience vary as a function of particular physical stimuli. In a similar vein, in his researchon problem-solving behavior in rats, the operationist Edward Chace Tolman, who believed thatbehavior was dependent on “cognitions” and “demands,” worked with a prior assumption, ac-cording to which the demand for a certain object varies relative to the degree with which the or-ganism has been deprived of that item, and that the vigorousness of searching behavior was, inturn, a function of this. Given these prior assumptions, Tolman took himself to be able to showexperimentally how particular desires vary as a function of deprivation.

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2. The terms operational definition and operationalization were, and are to this day, frequently used synonymously.

I will argue in the next section that these types of “definitions” did not have the status thatphilosophers usually associate with the term—i.e., they did not have the status of a priori knowl-edge or analytical truths. Rather, they were either temporary assumptions about typical empiri-cal indicators of a given subject matter, which allowed researchers to get empirical investigations“off the ground”, or they were presentations of the outcomes of experiments, which were as-sumed to individuate a given phenomenon particularly well. Thus, on my construal, they had amethodological function. Regarding the question of whether operationism was intended as anempiricist epistemology, it may be helpful to distinguish between two notions of epistemology.According to the first notion, the aim of epistemology is to provide a theory of what it would taketo justify existing systems of knowledge. According to the second, the aim of epistemology is toformulate guidelines for the acquisition of new knowledge. This latter notion of epistemologymay also be referred to as “methodology” (I take this distinction from Dingler, 1936/1988). Whilephilosophers are traditionally interested in the former, it is a contention of this article that earlypsychological operationists, as practicing experimental scientists, were interested in the latter.

On the methodological reading suggested here, an investigation of operational definitionsin psychology provides a framework for studying the process of concept formation in an ex-perimental context, or—to use the terminology of Hans-Jörg Rheinberger—of the coming intobeing of “epistemic things” (Rheinberger, 1997).

Operationism: The Positivist Reading

As is well known, the epistemological and semantic tenets of positivism were, for relatedreasons, soon recognized as problematic, and were subject to gradual changes and refinementsuntil the 1960s (Carnap, 1936/1937; Hempel, 1950, 1952, 1954; Quine, 1951). In a nutshell, itwas recognized that (a) there are statements, which scientists take to be justified, even though itis impossible to exhaustively rephrase them in terms of observation sentences, and (b) there arestatements about objects, which we intuitively recognize as meaningful, despite the fact that theconcepts that occur in those statements cannot be exhaustively defined in terms of operationsand resulting observations. The epistemological recognition led to the insight that a theoreticalsentence cannot be verified, but at best confirmed, by observations. This implies that the mean-ings of such statements cannot be reduced to methods of verification. Carnap realized this earlyon for statements containing disposition terms, stating that such terms can only partially be de-fined by observations (Carnap, 1936/1937), and later adding that many terms of a theory are im-plicitly defined by their place in the theory (Carnap, 1956). In a similar vein, philosophers calledinto question the notion of explicit definitions as requiring necessary and sufficient conditionsof application (Hempel, 1965). The recognition that observations can, at best, confirm scientificstatements went hand-in-hand with the introduction of a dichotomy between theory- and obser-vation language, such that sentences in the latter could be used to confirm sentences in the for-mer. This dichotomy, however, was soon called into question by reference to the theory-laden-ness of observation (e.g., Hanson, 1958), and because it relied on the distinction betweenanalytic and synthetic sentences, which was famously and radically attacked by Quine (1951).

With this simplified overview of the development of positivist philosophy in mind, wecan now appreciate that critics of operationism attribute to this doctrine various views thatwere held (or are commonly thought to have been held) by philosophers of the positivist tra-dition.3 First, there is the charge that operational definitions purport to provide necessary and

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3. The received view about positivist philosophy of science has recently been challenged (see Friedman, 1999). Inthe current article, I will not deal with this aspect of the problem. In other words, I will merely question the as-sumption that psychological operationists held the beliefs commonly attributed to positivists, not that positivists heldthe beliefs commonly attributed to positivists.

sufficient conditions of application. This, as was observed in the literature and reiterated bylater critics, would lead to “an uncritical multiplication of concepts” (Leahey, 1981; Weber,1940), and fly in the face of the scientific intuition that one and the same concept can applyin more than one situation, and that it can be applied even in the absence of an empirical con-dition of application (Hempel, 1954). Related to the worry about a multiplication of conceptsis the charge that operationists are antirealists about the referents of their concepts—i.e., thatone can arbitrarily introduce concepts regardless of whether they refer to something in theworld (e.g., Leahey, 1983; Michell, 1999). Second, there is the charge that operationists buyinto the analytic/synthetic distinction, believing statements that contain operational defini-tions to constitute a priori knowledge and thereby be analytically true, in which case “thereis nothing left to discover” (Green, 1992, p. 296), and any empirical evidence in support of adefinition would be circular, thus robbing it of its explanatory value (Leahey, 1981).

OPERATIONISM IN SCIENTIFIC CONTEXT: THE CASES OF STEVENS AND TOLMAN

In this section, I will elaborate on my case studies of Stevens’s and Tolman’s operationisms,showing that the positivist reading does not do justice to their operationisms. In the following sec-tion, this analysis will be complemented with brief historical outlines of how their operationismsoriginated and what was the nature of their contact with positivist philosophers of science.

Stevens’s Operational Treatment of Consciousness

Stanley Smith Stevens (1906–1973), who is mainly known for his work on psy-chophysics and measurement theory, arrived at Harvard for graduate studies in the fall of1931. Less than two years later, he defended his dissertation on the perceived attributes oftones. His advisor was E. G. Boring (1886–1968). After a few more years—having worked asa researcher in various other departments at Harvard—he accepted an offer to become an in-structor of psychology. During the second half of the 1930s, he published his four papers onoperationism (Stevens, 1935b, 1935c, 1936, 1939a). Since these papers are full of referencesto his psychophysical work on attributes of tones, I shall begin by outlining this work, as wellas the way Stevens uses the notion of “definition” there.

As mentioned above, Stevens’s psychophysical work was concerned with providing evi-dence for the existence of certain kinds of conscious auditory experience. While it had longbeen known that the subjective experience of loudness and pitch of a tone is a function of theenergy and frequency (respectively) of the physical stimulus (Boring, 1935), Stevens wantedto show that the subjective experience of “density” and “volume” of a tone also varies as afunction of variations in those two physical stimuli, thereby making the case that the experi-ence of density and volume (which had previously only been reported in a qualitative fashion)are genuine phenomena, which are distinct from other kinds of auditory experiences (Stevens,1934a, 1934b, 1934c, 1935a). In conducting this research, he presupposed that discriminatorybehavior in response to auditory stimuli could be treated as indicative of auditory experience.Based on this broad assumption, he then tried to develop an experimental design that wouldallow him to provide empirical evidence for particular kinds of experience (“volume” and“density”). Here, I will focus on his research on volume. Stevens came up with an experimen-tal paradigm, whereby subjects were given two tones of different frequencies and asked to reg-ulate the intensity of the lower one until the perceived volumes of both tones were equal. Itturned out that subjects increased the intensity of the stimulus with the lower frequency inorder to make its volume equal to the stimulus with the higher frequency, and that the requiredincrease in intensity was smaller for pairs of tones with high frequency. Thus, Stevens delin-


eated a unique pattern of responses to particular combinations of stimulus dimensions, whichhe treated as evidence for the existence of experienced tonal volume.

In what sense may Stevens be said to be offering definitions? I will begin by looking at hisassertion that “to experience is, for the purpose of science, to react discriminately” (1935c, p.521). Did he mean by this that the expression experience has the same meaning as discrimina-tive behavior? Did he mean that the presence of discriminative behavior is always a necessaryand sufficient condition for the correct application of the term experience? Based on his re-search, I think that this is clearly not what he has in mind. Rather, Stevens presupposed that ex-perience of tonal volume or density is phenomenal (and thereby, presumably, that the phenom-enal aspect is an integral part of the meaning of the term). The question, for him, is how to “getat” particular kinds of phenomenal experience in an experimental context. His assertion is thatthis can only be done via the behavior of the organism—i.e., that in an experiment, discrimina-tive behavior is a necessary condition for attributing conscious experience to an organism.Having devised an experiment that elicits such behavior in a regular fashion, he concluded,“[w]e are justified in saying that volume is a phenomenal dimension of tones” (1934a, p. 406).

Now, what about the “definitions” of tonal density and volume that Stevens offered as aresult of his empirical investigation? While Stevens seemed to think that the criteria offered inhis definition of tonal volume were sufficient conditions for the applicability of the term, Idon’t believe that he took them to be necessary conditions.4 This point is related to the ques-tion of whether he was an antirealist about the referent of the concept. I believe that the factthat he conducted research on the neurophysiological basis of the experience of tones (seeStevens & Davis, 1936, 1938) shows that he believed the concept of tonal volume to be phys-ically realized. This suggests that (a) he took the term consciousness to be more than a logicalconstruct or a useful fiction (i.e., that he was not an antirealist about its referent) and (b) hewould have been open to the possibility that it might in principle be detectable in more thanone way (i.e., that the operational definition he offered was not intended to state necessary con-ditions for the applicability of the term). The status of his “definition,” I would like to suggest,was that of an empirical finding that was taken to confirm the existence of a phenomenon. Thisleads us to our last question—i.e., whether Stevens took either of those two types of “defini-tions” to be a priori true or unrevisable. The answer, I believe, is quite explicit in his own writ-ings. He thought of definitions as factual statements that can be changed5:

[Definitions] take into account the state of factual knowledge at a given time. It is forgood reason that the discovery of new related facts may make a revision of the criterianecessary so that we may include or exclude the new observation from the class denotedby the original definition. . . . No concept can be defined once and for all: every conceptrequires constant purging to keep it operationally healthy. (Stevens, 1935c, pp. 519, 527)

Tolman’s Operationalization of Desires

Edward Chace Tolman (1886–1959) went to graduate school in the joint department ofphilosophy and psychology at Harvard University, where he received his PhD in psychology in

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4. I will return to epistemological problems with the assumption that the empirical result in question is a sufficient con-dition of application for the term (i.e., that it is sufficient evidence for the existence of the phenomenon in question).

5. An example of this is provided by Stevens (1935b) when he writes that his research shows Külpe’s definition of “sen-sory attribute” to be wrong. Külpe (1893) had defined this notion in terms of the criterion of “independent variability,”according to which a particular attribute of sensation can be varied by varying the associated stimulus-dimension (e.g.,frequency or pitch). Stevens’s research shows that some dimensions of auditory experience can only be varied by vary-ing both stimulus dimensions.

1915. He taught at Northwestern University for three years and then assumed a position at theUniversity of California at Berkeley in 1918, where he stayed for the rest of his life. In 1932,he published his book, Purposive Behavior in Animals and Men. In the second half of the1930s, Tolman published three papers in which he outlined his operationism (Tolman,1936/1958f, 1937, 1938/1958d). Tolman’s operationism has to be seen in the context of his re-search on problem-solving behavior in rats. As is well known, Tolman attributed to rats theability to form mental maps of their environments. As is less well known, he also assumed thatthe rat’s behavior is influenced by an internal drive or demand, which is dependent on the stateof biological need the rat is in at the time when the problem solving is required. Given thatTolman saw himself as a behaviorist, he recognized that it was problematic to posit the exis-tence of these two types of internal states (cognitive maps and drives), which he called “inter-vening variables.” His operationism was motivated by his desire to justify the practice of ma-nipulating the state of organismic need by providing evidence for the existence of these states.

In his first explicit paper on operationism, Tolman (1936) characterized this position as as-serting the existence of a set of intervening variables, certain functions whereby these interven-ing variables are related to particular independent variables (external stimuli), and certain func-tions whereby these intervening variables are related to particular dependent variables (types ofbehavior).6 While his presentation of his position is at times confused, I believe that, based onhis scientific work, the following rational reconstruction can be given: Intervening variables areposited internal entities or phenomena that are assumed to causally intervene between stimuliand outward behavior. As in the case of Stevens, we find, strictly speaking, two kinds of “defi-nitions” in the work of Tolman. To illustrate this, let us look at his papers, “An OperationalAnalysis of ‘Demand’” and “The Determiners of Behavior at a Choice Point” (Tolman, 1937,1938/1958d). As mentioned above, Tolman started out with a general presupposition about de-mands—i.e., that they can be affected by depriving organisms of particular types of objects (e.g.,the hunger demand can be affected by depriving an organism of food) and that this in turn hasan impact on behavior. Based on this prior assumption, Tolman conducted what he called a“defining experiment,” as a result of which he offered a mathematical equation of how the in-tensity of food-searching behavior in rats varies as a function of food deprivation.

Once again, we may ask in what sense Tolman can be said to be offering definitions here.First, it seems highly unlikely that Tolman intended his general notion of “demand” (as in-volving some kind of behavior in response to particular kinds of stimuli) to be exhaustive ofthe meaning of the term in ordinary language. Just as Stevens did not deny the subjective ele-ment of conscious experience, so Tolman did not deny the subjective character of certain men-tal states (see also Tolman, 1958c, 1927/1958b), but rather denied that this subjective feel couldserve as a basis for a privileged kind of data in psychology. Thus, as in Stevens’s case, the pointof the definition was to get an empirical handle on a phenomenon. Furthermore, when opera-tionalizing hunger in his research, the point, frequently, was not to do research on hunger perse, but to get a grip on this variable, in order to be able to control for this variable when test-ing hypotheses pertaining to other variables. For example, in his 1932 book (i.e., before thepublication of his operationism papers), Tolman operationalizes hunger in terms of “time sincelast feeding.” This, then, enabled him to conduct experiments about the question of whetherdifferent kinds of food are equally attractive to rats, given the same level of hunger (seeTolman, 1932a, for many examples of this strategy). When Tolman (1937) later provided whathe called a “defining experiment” for the notion of “hunger,” he was attempting to legitimatethe scientific practice he was already engaged in.


6. Some of these ideas are already expressed in Tolman (1935/1958g), albeit without using the term operation(al)ism.

We may now ask what he took the status of this defining experiment to be: Did it providea definition in the sense of necessary and sufficient conditions of application? Did he take itto refer to a real entity or was he an antirealist? Did he take the definitions to be a priori trueand unrevisable? With respect to the first two questions, the verdict is mixed. In Tolman’s writ-ings on operationism, we find statements to the effect that a theory is a complex mathematicalfunction, the terms of which are useful fictions. This is also how Tolman has been interpretedby MacCorquodale and Meehl (1948). However, I believe that we see here a certain lip servicepaid to the philosophy of logical positivism, whose proponents he had met by that time (moreabout this below). In his earlier work, it is clear that Tolman believed intervening variables tobe causally efficacious in the production of behavior. This suggests to me that he took them tobe real and that there might, in principle, be more than one way to identify them (i.e., the“defining experiment” does not provide a necessary, but at best a sufficient condition of ap-plication; see also Amundsen, 1983, in support of my claim that Tolman was not an antirealistabout the referents of his concepts). With respect to the last question, Tolman was less explicitthan Stevens. However, if we look at his writings, we find statements like the following: “[Thisbehavior] will be taken as empirical evidence for, and definition of, immanent expectancy”(Tolman, 1932a, p. 20). This suggests to me that for Tolman (as for Stevens), the line betweendefinition and empirical fact was not cut in stone, and that his “definitions” were working as-sumptions, based on what was known so far.

SOME HISTORICAL ORIGINS OF STEVENS’S AND TOLMAN’S OPERATIONISMS

In the previous section, I have shown that the “positivist” reading of operationism doesnot seem to fit the writings or practices of two operationists investigated here. In this section,I will complement these accounts with some aspects of the conditions that contributed to theemergence of these operationisms. The thesis of this section is that both Stevens’s and Tolman’smethodological views about operationism “co-evolved” with their scientific ideas and inves-tigative practices, which preceded their contact with logical positivists.

Stevens and the Psychophysical Tradition

An important factor toward the development of Stevens’s operationism was his advisor,Edwin Boring (1886–1968). Boring was important both in shaping Stevens’s understanding ofthe history of psychophysics (through his historical work, e.g., Boring, 1929) as well as his the-oretical and methodological views. With respect to the latter, Boring’s The Physical Dimensionsof Consciousness (1933) is especially important. About this book, Boring later wrote, “[t]uckedaway in my little book was this basic faith in operationism” (Boring, 1952, p. 44).7 Stevens wasclosely involved in the production of the book.8 This book served the dual purpose of articulat-ing a physicalist methodology for psychology and attempting to develop a modern-day varietyof Wundt and Titchener’s project of investigating elements of consciousness. Let us take a brieflook at both of these aspects (for a more detailed account, see Feest, 2002).

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7. In this context, Boring also mentions that this “basic faith” in operationism goes back at least to his paper “TheStimulus-Error,” published in 1921. Boring’s 1923 paper, “Intelligence as the Test Tests It,” should also be men-tioned. Both of these articles precede Stevens’s operationism by more than a decade. A detailed historical inves-tigation of the relationship between those earlier papers by Boring is needed to assess Boring’s own claims aboutthe matter.

8. This becomes apparent both in Boring’s preface to the book as well as in Boring’s autobiographical recollections(Boring, 1952) and Stevens’s private notebooks at the time. These notebooks, as well as Stevens’s correspondencewith Boring, are at the archives of Harvard University (shelf number HUG (FP)-2.45, Boxes 1 and 2).

Boring’s book had the aim of rejecting psychophysical dualism in its ontological andmethodological variety. Ontologically, I believe we can attribute to Boring some kind ofmind/brain identity theory. By asserting the existence of conscious experience, but stating thatit is identical with brain states, he distanced himself from both traditional substance dualismand from behaviorism. Here, I will focus on the methodological aspect.9 Boring wanted to re-ject the notion that psychology required a different methodology from other sciences. In argu-ing this, he distanced himself from Titchener’s introspectivism (see Boring, 1929). Boring’s1933 book was, in part, an attempt to reject Titchener’s methodological dualism and replace itwith a single, physicalist conception of scientific method. “Historically science is physical sci-ence. Psychology, if it is to be a science, must be like physics” (Boring, 1933, p. 6). For Boring,this meant that experience was a theoretical entity, to be inferred on the basis of behavior:“There is no way of getting at ‘direct experience,’ because experience gives itself up to scienceindirectly, inferentially, by the experimental method” (Boring, 1933, p. 6). Two years later,Stevens used a very similar formulation in arguing for his view that if “experience” was to bea scientific concept, it had to be amenable to the operational procedure, rather than being ac-cessed by some more “immediate,” introspective means: “Operationism requires that we dealonly with the reportable aspects of experience. Operational psychology knows precisely noth-ing of unreported consciousness” (Stevens, 1935b, p. 327).

Having talked about the origins of Stevens’s methodological commitments, let us now lookat the origins of his theoretical commitments. Here, I believe we can make out two strands. Onthe one hand, Stevens’s research was in the psychophysical tradition, going back to Fechner’s at-tempts to measure experience as a function of physical stimuli (Fechner, 1860).10 Stevens sawhimself as carrying forth this research, while explicating quite clearly the underlying assump-tions about empirical indicators of conscious experience. This need for explication was, I be-lieve, prompted by the heightened methodological awareness of the problematic status of con-sciousness as an object of scientific study in the aftermath of behaviorist critiques. The otherstrand, once again, takes us back to Boring’s book of 1933, Dimensions of Consciousness. It wasan explicit goal of this book to further develop Titchener’s notion of dimensions of conscious-ness, albeit stripped of Titchener’s dualism: “My book was a move away from Titchener, but italso served to make his dimensionalism clear” (Boring, 1961, p. 53). What Boring was refer-ring to in the latter part of the sentence here was Titchener’s structuralism—i.e., the project ofstudying the mind by dissecting it into its basic parts (Boring, 1933, also referred to this projectas “mental chemistry”). Given the focus of early experimental psychology on the study of sen-sation, it is not surprising that there was some psychological debate about sensations as basic el-ements of the mind (see Boring, 1933, 1942). According to Boring (and cited by Stevens), sci-entific interest in attributes of sensation goes back to Wilhelm Wundt (1893, Chapter 10), whocharacterized sensation in terms of attributes (quality and intensity), without, however, giving asystematic account of this analysis.11 Külpe (1893) gave a more systematic treatment of attrib-utes, distinguishing between quality, intensity, and duration (for all senses), and adding exten-sion for the senses of vision and touch. In addition, there were attempts to introduce mental el-


9. Stevens rejected Boring’s idea that substance dualism could be disproved on scientific grounds. In his private note-book of early 1933, he mentions a discussion he and Boring had about this (HUG (FP)-2.45, Box 1).

10. More recent predecessors dealing specifically with auditory experience were Helmholtz (1863) and Stumpf(1883,1890).

11. While it has been suggested that Boring’s historical writings had an agenda (e.g., O’Donnell, 1985), I am here re-lying on his accounts, as my interests do not lie with giving a historically accurate account so much as understandinghow Stevens—who learned his history from Boring—situated his own approach. (In his obituary for Boring, Stevensprofesses that Boring’s History of Experimental Psychology is one of two books that he read twice.)

ements other than sensations.12 The Titchenerian tradition of American psychology later ruledout images and feelings as basic elements of consciousness, thereby equating consciousnesswith sensation (for a more detailed account, see Boring, 1933). The structuralist focus on sen-sations as basic elements of consciousness came under attack with the rise of Gestalt psychol-ogy. Boring attributed to Titchener a theoretical response to this state of affairs, which, however,Titchener never fully worked out. According to this view, consciousness is to be described interms of four basic dimensions (quality, intensity, extensity, and protensity; see Titchener, 1929),with each sense modality having different attributes that can be classified under these dimen-sions.13 It was this idea that Boring wanted to argue for in his 1933 book.

Unfortunately, Boring’s book was a flop and only sold 105 copies in the first 17 years (cf.Boring, 1961, p. 53). According to Stevens, this lack of success was, in part, due to the factthat Boring had not been able to provide experimental evidence for his claim that conscious ex-perience has certain attributes, or dimensions. At that point in time, Stevens’s work on tonal at-tributes, which would have demonstrated this point, had not yet been completed: “[S]ome ofthe research that [Boring] was directing [i.e., Stevens’s own research] was soon to clarify therelation between tonal sensation and its four attributes: pitch, loudness, volume, and density”(Stevens, 1968, p. 597). The relevance of Stevens’s research on tonal attributes to Boring’swork on dimensions of consciousness can also be gathered from the fact that Boring made thiswork a central point of reference in his 1935 article “Attributes of Sensation” (Boring, 1935).The relevance of Stevens’s operationism to his experimental work on tonal attributes, in turn,can be inferred from the fact that Stevens devoted a whole section of his paper “TheOperational Definition of Psychological Concepts” (Stevens, 1935c) to the discussion of tonalattributes. Thus, my thesis is that the emergence of Stevens’s operationism was closely relatedto his psychophysical work on tonal attributes, which in turn raised methodological issuesabout how to conceptualize and measure such attributes.

Tolman’s Notions of Instincts and Instrumental Reasoning

Important cues as to the origins and enabling conditions for Tolman’s operationism can befound in the nature of the intervening variables that he proposed (i.e., “demands” and “cogni-tions”). In this section, I argue that (a) attempts to get a scientific grip on “demand” concepts goback to the mid-1920s and can be traced back even farther to his student days, and (b) his answeras to how to investigate (i.e., operationalize) the referents of such concepts is closely related tohis notion of “cognition,” which also had an interesting development within his thought.14

Within Tolman’s work, we find reference to both of these variables (albeit under differentnames) as early as 1925 (e.g., Tolman, 1925/1958h). Tolman believed that any given action isalways going to be determined by both of these types of intervening variables, where the for-mer provides the motivating force for a behavior and the latter enables the organism to repre-sent knowledge about the world. Tolman needed to conceptualize these notions such that theycould be experimentally teased apart (e.g., by holding one constant and observing the effect onthe other, which obviously required some prior assumptions as to what are typical causes andeffects of such internal states). Equally important, however, he needed to come up with somebehavioristically respectable account of why it was permissible to appeal to such “mentalistic”

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12. For example, Külpe tried to find elements of (imageless) thought, and Titchener argued that there were threeclasses of mental elements: sensations, images, and feelings (Titchener, 1910).

13. The distinction between dimensions and attributes is not completely clear. Boring admits that “[t]he dimensionsof consciousness are the immediate successors to the old attributes of sensation” (Boring, 1933, p. 23).

14. The parallel between Tolman’s epistemological views and his conceptualization of “cognition” has also been notedby Laurence Smith (1986). The present account is inspired by (but not identical with) Smith’s analysis.

notions at all. This is particularly apparent in his writings about demands. This question, forhim, had two aspects: (1) what criteria could be used when describing a behavior as purposive(this was related to his notion of “molar” behavior) and (2) on what grounds might it be per-missible to explain a behavior by appeal to an internal motivating state (see Tolman,1925/1958a; 1926). In his development of how he dealt with these questions, it is important torecognize the impact of McDougall’s notion of instinct. In fact, I believe that Tolman’s think-ing about demands has to be viewed as an attempt to put McDougall’s notion of “instinct” onan objective, behavioral footing. Tolman had first come across McDougall’s work in a seminarhe took with one of his Harvard professors, Ralph Barton Perry (1876–1957), while he was agraduate student there (Tolman, 1952). Perry’s own attempts to develop a scientific notion of“value” are also significant here (see Perry, 1926). In his articles leading up to this work (Perry,1918, 1921a, 1921b, to which Tolman, 1920, 1922, appealed), Perry explicitly endorsed botha doctrine of behaviorism and the notion that behavior has to be scientifically explained by ap-peal to beliefs and desires. Lastly, one of Tolman’s other Harvard mentors, Edwin B. Holt(1873–1946), has to be mentioned, who—among other things—focused on the issue of how itis possible to describe purposive behavior in objective (nonteleological) terms (1915).15

Tolman thought of demands as providing the drives that motivate biological organisms toengage in instrumental reasoning. His notion of “cognition,” thus, was one of instrumental rea-soning. According to Tolman’s theory of purposive behavior, environmental features are cog-nitively represented in terms of how they can be used or manipulated in order to attain certaingoals. Or, to use Tolman’s own terminology, environmental features are represented as “means-objects,” which figure in “cognitive postulations” (or hypotheses) as to what would happen ifthe object were to be manipulated in a certain way (Tolman, 1932a). Thus, for Tolman, cogni-tive representations are always formed relative to certain goals (e.g., the goal to get to the food)and they involve expectations as to the outcomes of hypothetical actions (e.g., “if I were to takethe left lane, this would get me to the food”). I believe that we can make out a variety of fac-tors that may have enabled Tolman to move toward this view.

One such factor was Robert Yerkes’s (1876–1956) research on primate intelligence. In 1916,Yerkes published a monograph, The Mental Life of Monkeys and Apes, based on research carriedout in the spring of 1915, in which he reported several experiments that he conducted with orang-utans, which (while quite ambiguous) he took to demonstrate their capacity for instrumental rea-soning. It is known that Tolman took a class on comparative psychology with Yerkes at Harvardaround 1915.16 Another important intellectual stimulation was German Gestalt psychology.During his early career, Tolman undertook two visits to Germany (one after his first year of grad-uate school, in 1911, and one in 1923), where he stayed with Kurt Koffka, though each of thesestays was only brief.17 In his later work, Tolman emphasized the importance of Kurt Lewin’s no-tion of objects having a certain “valence” (see Tolman, 1952, but see also Tolman, 1932a, 1932b),but also his notion of molar behavior as being more than the sum of physiological processes, aswell as his usage of the expression sign-gestalts, indicates his closeness to certain Gestalt psy-chological ideas, though he took this latter notion to be broader than theirs, in that it emphasizedthe relationship between perception and action. For example, a chair might be mentally repre-sented as “that chair, if placed against the wall, can be stood upon like a stepladder to reach this


15. See Feest (in press) for a more detailed account of the impact of Perry and Holt on Tolman, and a discussion ofhow Tolman’s treatment of drives was located in the instinct debate of the 1920s.

16. It may also be speculated that Wolfgang Köhler’s research on primate intelligence, conducted on Tenerife aroundthe same time, may have had an indirect impact on Tolman, as Köhler and Yerkes were corresponding (Ash, 1995;Kohler, 1917).

17. I owe this information to Nancy Innis.

picture” (Tolman, 1933/1958e, p. 80). Two other important figures to be mentioned here are EgonBrunswik (1903–1955) and David Krech (1909–1977). Tolman met Brunswik while on sabbati-cal in Vienna in 1933/1934 (after the publication of his Purposive Behavior, but before the pub-lication of his papers on operationism), and they published a paper together (Tolman &Brunswik, 1935). According to Tolman’s own account, Brunswik “gave me new insight into theessentially achievement character of behavior” (Tolman, 1952). Apart from significant differ-ences between the two, it seems to me that Brunswik’s impact consisted of underscoring an el-ement that was already present in Tolman’s thinking—i.e., the notion that all behavior is basedon hypotheses about the nature of the environment, which may or may not be correct. The majornew insight that Tolman picked up here (which had, of course, been implied by his previouswork) was the notion that all knowledge is fallible. Tolman recognized that this idea was simi-lar to his own notion that behavior is guided by sign-gestalts. Since sign-gestalts were essen-tially hypotheses about the outcomes of hypothetical manipulations, there was always a chancethat they might not lead to the desired outcomes (i.e., that they were mistaken). In their jointpublication, Tolman and Brunswik spelled out these basic ideas in more detail, essentially stat-ing that both with respect to perception as well as action, the organism faces a degree of uncer-tainty, which the organism copes with by trying to come up with hypotheses that maximize theprobability of success. The notion that sign-gestalts are hypotheses had already begun to appearin the context of Tolman’s experimental work shortly before his encounter with Brunswik. Inparticular, it was tied to work that he conducted with his student Isodore Krechevsky(Krechevsky, 1932a, 1932b; Tolman & Krechevsky, 1933).18 This (and more) work was latersummarized in Tolman’s article on cognitive maps in rats (Tolman, 1948).

With this overview, I hope to have given some plausibility to my thesis that Tolman’s op-erationism was an attempt to legitimate his talk about intervening variables, and that his viewson how to conceptualize these variables went back to his student days. Furthermore, I think thathis views about cognitive representations in rats (conceived as hypotheses as to what wouldhappen if the object in question were manipulated) were similar to his own practice of opera-tionalizing concepts—i.e., as referring to hypothetically posited objects, which, if experimen-tally manipulated in a certain way, are expected to behave a certain way (thereby confirminghypotheses about the existence of such objects).

The Impact of Positivism

The above outlines of the origins of Stevens’s and Tolman’s operatonisms are not intendedto be exhaustive. For example, I have neglected to mention a variety of factors that may havecontributed to my main actors’ intellectual development.19 Furthermore, by pointing to the con-texts in which certain methodologies originated I have not thereby provided an analysis of whythey were adopted. For example, while claiming that the basic tenets of these two varieties ofoperationism were similar, I have only hinted at possible explanations for why these positionsended up looking so similar (namely, by reference to the methodological distrust of traditionalintrospectivism and mentalism, which both of these scientists had adopted from behaviorism),despite the very different origins and research interests of their proponents.

While my historical outlines were supposed to show (among other things) that these opera-tionisms were already being contemplated before the scientists in question encountered repre-

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18. Today, Krechevsky is better known by the name “David Krech,” which he adopted in 1943 (the year he got mar-ried) in order to spare his son the anti-Semitism he had encountered throughout his professional life (Krech, 1974).

19. For example, Stevens’s religious background as a Mormon, or his involvement with the American AcousticalSociety, or Tolman’s friendships with the pragmatist philosophers, C. I. Lewis and S. Pepper.

sentatives of logical positivism, this is not to deny that both Stevens and Tolman did indeed en-counter representatives of logical positivism, and that this had an impact on how they formulatedtheir operationisms. I believe that those references were largely rhetorical, aimed at backing uptheir views by appealing to cutting-edge philosophy of science. Let us begin with Stevens.Herbert Feigl, a member of the Vienna Circle, was at Harvard in 1930, but this was beforeStevens’s time. While it has been asserted that Feigl brought Bridgman’s operationism to the at-tention of Harvard psychologists (see Green, 1992; Moyer, 1991), this is contradicted by Boring’sown retrospective account, according to which both he and Stevens were unaware of Bridgman’soperationism when they were working on the Consciousness book (Boring, 1961). At any rate, ifFeigl (via Boring) left any traces in Stevens’s thinking, this is not reflected in Stevens’s early note-books of 1932 and 1933. Hardcastle (1995) has made the case that Stevens’s knowledge ofGerman was limited and that he was therefore unlikely to have been exposed to logical positivismbefore Carnap’s 1934 contribution to the journal Philosophy of Science (Carnap, 1934). However,by the mid- to late 1930s, Stevens did know positivist philosophers of science, got involved withthe Unity of Science movement in the late 1930s, and explicitly related his operationism to thismovement in his 1936 paper.20 But this strikes me as an ex post adoption of terminology, ratherthan reflecting a genuine impact on the content of his own operationism.

With respect to Tolman, I would like to make a similar point. As I showed in the casestudy, the essential components of Tolman’s operationism were already implicit in his writ-ings from at least the mid-1920s onward. The remaining question is what prompted him toarticulate this position as an explicit doctrine in the mid- and late 1930s. An obvious answer,which Tolman confirmed in his 1937 paper, is that in the 1930s he came across S. S.Stevens’s and Bridgman’s formulations of operationism. Another obvious suggestion is thatwhile in Vienna, Tolman got acquainted with members of the Vienna circle, and possiblyread Carnap’s “Psychology in Physical Language” (Carnap, 1932). There is good reason tobelieve that Tolman attended meetings of the Vienna Circle, based on his friendship withBrunswik, as well as the fact that Schlick had been a visitor at the Philosophy Departmentat Berkeley a couple of years earlier. Also, Tolman was approached to present a paper at the1936 Unity of Science congress, but was unable to attend (the paper he had planned to pres-ent was his 1937 paper on operationism). However, I would like to make the case that he wasonly adopting a label for a position that was already fairly consolidated and that differedfrom the kind of position that is usually associated with positivism.

EPISTEMOLOGICAL PROBLEMS WITH OPERATIONISM

The aim of my historical case studies was to argue that operationism in psychology wasnot identical with, nor was it significantly influenced by, an empiricist epistemology or a ver-ificationist theory of meaning. According to this analysis, both scientists in question wanted tolegitimate their research on “mentalistic” topics by providing empirical criteria of applicationfor their concepts.21 These empirical criteria of application were “definitions” insofar as theyspecified features that these authors took to be indicative of their purported subject matter—thereby enabling them to do research on that subject matter—but they were not intended to ex-haustively provide the meanings of the concepts in question, or to be unrevisable. However,


20. Stevens presented a paper, entitled “On the Problem of Scales for the Measurement of Psychological Attitudes,”at the Fifth International Congress for the Unity of Science, which was held at Harvard University in September1939 (see Stadler, 1997, p. 431).

21. I do not claim that this motivation can be generalized to other operationists. As was remarked by an anonymousreferee, my interpretation might prove to be problematic when it comes to Skinner’s operationism.

while my analysis may imply that psychological operationism cannot have inherited the spe-cific problems of empiricism and verificationism, it does not imply that it does not have prob-lems of its own. The problem I want to discuss here is that of circularity.

The issue is that it would be circular to justify the validity of a concept by referenceto the operations that led to its introduction.22 This was one of the problems that behav-iorists had made out in traditional mentalism. As argued above, operationism was, in part,an attempt to deal with this problem. So, if operationism cannot avoid circularity (as hasbeen suggested by critics), it would have failed to meet this goal (this problem is alsopointed out by Green, 1992, p. 300). One possible way of avoiding circularity would be toprovide evidence for a given thing (e.g., Stevens’s tonal density and volume or Tolman’sdemand) by showing that it can be detected by different means (i.e., different experimen-tal operations). If I am correct in my contention that both Stevens and Tolman were real-ists about the referents of their concepts, then it is plausible to assume that they wouldhave believed this to be permissible. Indeed, by the mid-1940s, this was explicitly allowedby proponents of operationism (Boring, 1945). But none of the early operationists wereable to provide criteria that would settle how to determine that two operations do indeed“get at” the same object (i.e., operationalize the same concept). I believe that part of theappeal of operationism was its cautionary aspect, in that it advised scientists not simply toassume that one and the same concept applies under very different circumstances (i.e.,when different operations are used).23

A related problem is that—given the assumption that the cognitive system is very com-plex, and given all the assumptions that go into an experimental setup—one may be skepticalof whether a particular experiment really individuates any one cognitive process in pure, un-contaminated form (or at all, for that matter). In other words, did Tolman really have groundsfor assuming that his “defining experiments” on demands, even if such a cognitive entity re-ally exists, actually reflected demands, rather than being the output of a complex interactionof any number of cognitive processes that are required when the rat performs in a maze? Asdescribed by Grace (2001), both of these problems were addressed by subsequent method-ological developments within psychology. On the one hand, the convergent/discriminant op-erations (or multitrait-multimethod) approach suggested correlating the results of differenttests of the same purported phenomenon, and of similar tests about different purported phe-nomena (Campbell & Fiske, 1959). On the other hand, the converging operations approachsuggested designing experiments that would specifically test alternative hypotheses to ac-count for the data (Garner et al., 1956).

I do not intend to go into the details of these methods or whether they successfully dealwith the problems just outlined, let alone whether psychologists today can generally be saidto apply them correctly. Rather, the point of this section was to isolate what I take to be aproblem that critics of operationism might legitimately be concerned about. However, asmentioned earlier, in response to Grace’s article, several authors suggested that there issomething deeply wrong with operationism, which cannot be fixed by superficial method-

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22. By the notion of validity, psychologists mean that a concept or test refers to what it is thought to refer to. Thisis different from the notion of validity in logic.

23. For example, “Operationism is the manner in which the present generation utters the familiar cry of science, ‘becareful’” (Pratt, 1939, p. 81). Even Bridgman later claimed that all he had intended to say in his 1927 book was that“[operationism] is a technique of analysis which endeavors to attain the greatest possible awareness of everythinginvolved in a situation by bringing out in the light of day all our activity or operations when confronted with the sit-uation” (Bridgman, 1938, p. 130).

ological innovations. In the following section, I will discuss the questions of what this de-bate might be about.

WHAT IS THE DEBATE ABOUT—WHAT SHOULD IT BE ABOUT?

Let us start with the charge that operationism—contrary to its own assertions—is notmetaphysically neutral (Bickhard, 2001; Green, 1992, p. 314). I believe that this charge is di-rected at the positivist rejection of metaphysics, and the idea of a neutral observation language.Once again, it might be helpful to keep in mind the difference between the positivist and theoperationist project. Positivists attempted to formulate an epistemology that was metaphysi-cally neutral (e.g., Carnap, 1931). Operationists (on my construal) attempted to formulate amethodology for an empirical psychology, which was sensitive to problems with introspec-tivism and mentalism, and which forced psychologists to explicate their prior assumptionsabout how to interpret observations. Kendler (1981) also emphasizes this point when he arguesthat when there is a disagreement between empirical psychologists about a given phenomenon,it may turn out that the disagreement is not about the empirical results, but about how to oper-ationalize the concept.

Let us turn to a second, related critique of operationism—that it implies a particular no-tion of what it means to be scientific, which in turn has an impact on how psychological phe-nomena are conceptualized and what kinds of psychological phenomena can be scientificallyinvestigated at all. According to this critique, the charge is not merely that operationism is notmetaphysically neutral, but that it promotes a particular metaphysical picture. One version ofthis charge is that operationism is intricately tied to quantitative and experimental methods—i.e., an understanding of psychology as a natural science. For example, Leahey (1983) arguesthat a naturalistically conceived psychology (which operationism—according to him—standsfor) cannot account for the phenomenon of intentionality. What I take him to be saying here isthat operationism is incapable of employing qualitative or hermeneutic methods, which woulddo more justice to the psychological subject matter. The first of these two assertions does notstrike me as self-evidently true, but it certainly warrants further discussion. More importantly,though, I would like to argue that operationism is not committed to any particular notion of thesubject matter of psychology. While it is true that Stevens and Tolman (as we have seen) wereindeed proponents of a quantitative and experimental method in psychology, I believe that thiscoincidence is historically contingent. To put it quite bluntly, all empirical psychologists haveto operationalize their concepts. And all empirical psychologists have to argue for their resultsby laying open both their conceptual presuppositions and their empirical data. Viewed this way,the issue seems to be whether psychology can be an empirical science at all.

One last critique of operationism is that psychologists frequently confuse definitions andfacts—i.e., they think that operational definitions can substitute for theoretical work about thereferent of the concept. In this vein, Christopher Green quite appropriately points out that “al-though operational definitions might have a role to play in piloting nascent thought about agiven phenomenon, they cannot ultimately replace the fruits of hard, rigorous thought” (Green,1992, p. 315). While agreeing with this assessment, I believe that he is expressing a critique ofcertain widespread research practices, not of operationism per se.24


24. Gerd Gigerenzer has suggested to me that the proliferation of operationally defined empirical concepts at the ex-pense of theoretical work might be due to funding policies that reward empirical work more than theoretical workand provide an incentive for psychologists to inflate the significance of a given empirical effect. Following up thissuggestion might itself be an interesting historical and sociological project.

Summing up this section, I believe the debate mistakenly focuses on the tenability of op-erationism, where in fact it should be about the question of preconditions for psychology as anempirical science and about the question of whether psychologists exhibit the requisitethoughtfulness in their research. Insofar as there is agreement that psychology can be an em-pirical science, the debate should then be about what are adequate concepts and how (notwhether) to operationalize them, and how (not whether) to validate them. This task is far fromtrivial, and it may turn out that the gaps between different (e.g., qualitative vs. quantitative) ap-proaches within psychology cannot be bridged. However, I believe that the gap, ultimately, isnot one between proponents and opponents of operationism.

CONCLUSION

In this article, I have provided a conceptual analysis of the notion of operationism inpsychology. This analysis was based on a historical investigation of the operationisms oftwo early proponents, S. S. Stevens and E. C. Tolman. Two construals of operationism wereintroduced, a “positivist” and a “methodological” reading. It was argued that while criticsof operationism frequently assume a positivist reading of this position, an analysis of theways in which operationism was applied in Stevens’s and Tolman’s research suggests amethodological reading, according to which operational definitions have a pragmatic roleto play in psychological research, but are not taken to be necessarily true or unrevisable.This analysis was further backed up by a historical study of the origins of both Stevens’sand Tolman’s operationisms, which revealed that neither one of them had any significantcontact with proponents of positivism in philosophy, until the substance of their positionwas already in place. I then presented an analysis of some epistemological problems withoperationism, and the ways in which methodological writings in the 1950s tried to addressthese problems. Lastly, I claimed that the current debate about operationism is really abouta couple of deeper points of contention, and I suggested that these should be addressed in-dependently of the issue of operationism.

ACKNOWLEDGMENTS

I would like to thank Bob Olby who first encouraged me to pursue this project in agraduate class I took with him in 1998. I also thank the members of my dissertation com-mittee, especially my advisor, Peter Machamer, and my friend Stephanie Koerner. Thanksto audiences at the 2003 ESHHS-meeting and at the Max Planck Institute for the Historyof Science as well as to two anonymous referees for helpful remarks. I am grateful to NancyInnis for sharing information about Tolman with me. Last but not least, many thanks to RayFancher and to the members of the Wiley production department.

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