Mainstream psychological scientists in this pe- riod worked primarily in the neobehaviorist mode, attempting to show that lawful relations between stimuli and responses indicated how organisms adapt to varying conditions, that is, how organisms learn. Some neobehaviorists at- tempted to derive formal systems that would describe the laws of behavior.
The study of a small albino rodent, Rattus norvegicus var albinus, in an enclosed space became the predominant activity in North American psychology laboratories for nearly 60 years. The behavior of the rat under controlled conditions of stimulation was taken as a stand-in
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for the likely behavior of humans. Psychologists who embraced this approach argued that the learning demonstrated by these rats was analogous to the adaptation of other organisms.
Several variants of this approach came to the fore, sometimes termed behaviorism, neobe- haviorism, or in the work of Burrhus Frederic Skinner (1904–1990), radical behaviorism.
Behavioral psychology became the mainstream of North American experimental psychology. As we show in this section, this had implications for the philosophy of science, for methodology, for technology, and for the organization of scientists.
Watson declared in 1913 that ‘‘psychology as the behaviorist views it is a purely experimental branch of natural science. Its theoretical goal is the prediction and control of behavior. Intro- spection forms no essential part of its methods’’
(p. 158). You may recall that in Chapter 3 we discussed Watson’s development of behaviorism within the context of the Progressive Era and showed how the kind of psychology he advo- cated fit well with that era’s search for order and rationality in society. We also indicated that Watson was not the only person at the time to argue for a focus on observable behavior rather than unseen conscious states as the appropriate data source for a scientific psychology. Watson was powerfully positioned, however, to make the case. He was the editor of Psychological Review, chair of the Psychology Department at the Johns Hopkins University, and elected president of the APA for 1915. Still, as historian Franz Samelson (1981) has pointed out, the field of psychology did not immediately move lock, stock, and barrel to behaviorist psychology.
In this era, most academic psychologists who were actually doing experimental work (that has always been only a relatively small proportion of those who were trained as scientists) were still us- ing introspection and reaction-time methods to study phenomena such as attentional processes; a few psychologists were using recently developed psychological tests. The theoretical framework was predominantly functionalist (processes of conscious states), although many worked
within the structuralist (mental contents) model developed by Cornell University psychologist Edward Bradford Titchener (1867–1927). By the early 1920s, however, the terms ‘‘behavior’’ and
‘‘behaviorist’’ were being widely used without necessarily indicating Watson’s behaviorism.
By the late 1920s, enough psychologists were doing behavioral research to indicate that the mainstream of American psychological science was becoming behaviorist.
What might have facilitated this change? One factor was that those psychologists who were graduate students and early career psychologists when Watson called for a focus on behavior were by the mid- to late 1920s moving into leader- ship positions, and they had certainly been more receptive to Watson’s emphasis on observable behavior. Second, this generation of psycholo- gists seemed to experience ‘‘physics envy’’ more keenly than their predecessors. That is, as the natural sciences like physics were making such huge strides and garnering great public acclaim (e.g., the work of Albert Einstein and Niels Bohr on relativity theory and quantum theory), the datum of an unseen consciousness carried little weight among their scientific colleagues.
The annual meeting of psychologists was held in conjunction with other scientists, including physicists, making this state of affairs perhaps painfully obvious. Behavior, however, was ob- servable, thus potentially predictable and subject to control in a scientific milieu that placed a high value on prediction and control. As noted, behav- iorism fit better with the political culture of the time. It was easier for those in power to grasp how a behaviorist psychology could improve society than it was for them to understand how a psy- chology of conscious mental states could do so.
Scientific contributions and developments also propelled the move toward behaviorism.
One was the eruption of an argument in Germany about psychology’s status as a science. This seems obscure, perhaps, but it proved important for reshaping the methodology of scientific psychology. The genesis of this debate was the split between Wilhelm Wundt (1832–1920) and
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his former student, Oswald K ¨ulpe (1862–1915), over the appropriate philosophy of science for Psychology. At the time the controversy began, K ¨ulpe was Wundt’s chief assistant in the Psychology Laboratory at the University of Leipzig. As we noted in Chapter 3, Wundt argued that many psychological phenomena could not be studied experimentally. Those that could be so studied—simpler cognitive processes—obeyed laws of psychic causality rather than physical causality. For Wundt, psychology was not and could not be a strictly natural science. K ¨ulpe came to disagree, and when he left Leipzig for a position at W ¨urzburg, he made his disagreement open and engendered a controversy that continued for many years. At the heart of the disagreement with Wundt was a different conceptualization of science. K ¨ulpe embraced thepositivismof the physicist Ernst Mach (1838–1916) and philosopher Richard Avenarius (1843–1896). This positivism asserted the primacy of experience as the basis of knowledge; that is, that the experience of the observable world is foundational to science.
Experience is experience; thus, there are not two kinds of experience, mental and physical. In this approach to psychology, mentalistic explanations are not acceptable. Wundt, of course, had argued that psychological or ‘‘psychic,’’ as he termed it, events have psychological causes. His experimental psychology was constructed on mentalistic explanations.
K ¨ulpe and his colleagues and students at W ¨urzburg proceeded to develop an experimental psychology on a positivist basis and to include in it complex mental processes, such as thought, that Wundt had declared off-limits. Theirs was to be a scientific psychology of experience. The redefinition of psychology in this way, based on the experienced, observable physical world, proved crucial for the future of Psychology. It meant that Psychology would focus on what could be observed rather than internal mental states. In the American context, which as we have seen, was (and is) practically or pragmatically oriented, this provided another justification for
what came to be labeled behaviorism. As Watson had argued, if psychology were to be a natural science, it had to give up its focus on the unseen mental states and turn its focus to what could be observed, the behavior of organisms. By the late 1920s and into the 1930s, American psychology became even more deeply infused with positivism through such constructs as operationism and logical positivism, both direct descendants of Machian thought. In particular, these constructs were embraced by several psychologists who came to be labeled neobehaviorists.
Neobehaviorism
During the 1920s, the mainstream of psycholog- ical science embraced the study of behavior. Im- plicit in this approach was the Darwinian notion of evolution by natural selection. Humans are part of nature; thus, adapting to their surround- ings is key to survival. Metaphors employed for this adaptation included adjustment and learning, which could be observed in behavior.Conditions of learning could be experimentally manipulated;
thus, the scientific laboratory was the appropri- ate site for the discovery of its laws. Given the continuity of species demonstrated in Darwinian theory, the behaviorists argued that nonhuman animals could be used as stand-ins for humans in studies of learning. As noted earlier, the animal that came to be preferred for this analogous role was the white rat.
By the 1930s, two new important influences had been introduced into behaviorism, giving it its name, neobehaviorism. Operationism was taken from the work of physicist Percy Bridgman (1882–1961). In his book, The Logic of Modern Physics (1927), Bridgman argued that each construct introduced by scientists should be specified in terms of how it is measured. An operational definition is the set of methods or techniques used to measure the construct. No references to mental processes or internal feeling states were allowed. So, in the psychology of the time, a scientist might operationally define hunger by giving the exact weight of the rat and
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exactly how long the rat had been without food.
Logical positivismwas the influential philoso- phy of science based on the positivism of Mach that decreed that all scientific constructs had to be linked to observable events. In the United States, to which several of these philosophers immigrated, this group of philosophers was called the Vienna Circle. In Vienna, they were known as the Ernst Mach Society.
Both operationism and logical positivism were incorporated into the new behaviorism by the 1930s. Both were powerful influences that many new leaders of experimental psychology hoped would give their science greater legitimacy and would help confirm that psychology was, indeed, a natural science.
Watson’s theoretical approach had been the conditioned reflex model developed most com- pletely at the time in the laboratory of Russian physiologist Ivan Pavlov (1849–1936).Clark Hull (1884–1952), one of the most prominent neobe- haviorists, also adopted a conditioned reflex model for his ambitious program of research.
Hull had hoped earlier in his life to be an engineer, but a bout with polio left him slightly disabled and his application to engineering programs was rejected. He taught school for a period before returning to college, where he eventually earned his doctorate in psychology at the University of Wisconsin. He conducted applied research in the first decade or so of his career and was recruited to Yale University in 1929 to fill a need for someone with a strong interest in applied work.
Yale, at this time, had established the In- stitute of Human Relations with a large grant from the Rockefeller Foundation. The institute was interdisciplinary, and research there was in- tended to shed light on the social problems of the day. As we noted at the beginning of the chapter, philanthropical foundations were heav- ily committed to supporting interdisciplinary and cooperative scientific research programs. For the Rockefeller Foundation, this was an effort to see whether large-scale philanthropical sup- port could facilitate social engineering through
scientific research. Hull proved one of the most adept of the Yale scientists in using this support to further his own research aims, if not those of the institute or the Rockefeller Foundation.
Even as Hull began his systematization of learning principles at Yale, he kept his inter- est in the applicability of his research to human problems. With colleagues, for example, he stud- ied alcohol consumption. He also had ambitions to understand even more serious disruptions of normal human functioning, the psychoses. He proposed using a modified form of Pavlovian conditioning to study these problems. One Rock- efeller administrator described Hull in 1934 as the American Pavlov, who ‘‘uses Yale sopho- mores instead of dogs’’ (Weaver, 1934). In fall 1935, Hull decided to initiate a program to corre- late the tenets of psychoanalysis with conditioned reflex theory. He drew upon work being done in
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Chicago that suggested several possible links be- tween psychoanalysis and Pavlov’s conditioned reflex theory. Based upon this work, Hull sought to establish a research program that integrated conditioned reflexes and psychoanalytic therapy techniques to address such serious problems as psychoses, juvenile delinquency, bullying, and frustration. Hull’s efforts were pointed toward bringing the irrational (exemplified by psycho- analysis) under the control of orderly, systematic science and were part of his larger project for a unified science.
As Hull, his graduate students, and his post- doctoral fellows worked on these projects, the theoretical apparatus they developed grew ever larger. Hull was convinced that the principles of learning, of an organism’s adjustment to the environment, could be captured as a set of math- ematical theorems and corollaries. Learning was mathematically described in terms that specified linkages among drive (e.g., hunger drive, oper- ationally defined as hours without food), habit strength, reinforcement, and several other vari- ables. It was a complex theory that required constant adjustments, with new findings added in mathematical formulas to already complex formulations. Eventually, this system grew too elaborate to test, and many adherents withdrew from trying to do so. Nevertheless, during the heyday of Hull’s system (1935–1952), it was the most cited body of work in American experimen- tal psychology.
Edward Chace Tolman (1886–1959) is the other major neobehaviorist we discuss. Tolman brought to his work a more broad-minded view of experimental psychology than did Hull.
Nevertheless, Tolman argued that all we need to know about human behavior could be learned from experiments with rats.
Tolman grew up in a devout Quaker home.
His brother, Richard, became a physicist and was one of the scientists who helped develop the first atomic bomb. Like his brother, Edward graduated from the Massachusetts Institute of Technology with a degree in theoretical chem- istry. However, he was drawn to philosophy and
enrolled in graduate study at Harvard University to pursue his interest. He became interested in psychology through his professors at Harvard and a summer spent in Germany, where he met the young Gestalt psychologist Kurt Koffka (1886–1941). Course work in comparative psychology introduced him to Watson’s recent work in behaviorism, and Tolman eventually came to see the behaviorist approach as the route he wanted to follow. He lost his first job at Northwestern University during World War I because of his pacifism. Tolman then took a po- sition at the University of California, Berkeley, in 1918, where he spent the rest of his career.
The psychology building at Berkeley is named for him.
Tolman dedicated his most influential book, Purposive Behavior in Animals and Men(1932),to the white rat. As the title indicates, Tolman’s ap- proach assumed that behavior was goal directed.
Unlike Hull and many other neobehaviorists, Tolman did not accept that learning consisted of chains of conditioned reflexes. Rather, the rat, and by extension, the human, was constantly learning about the environment, but much of this learning was latent; that is, it would not be demonstrated until the occasion called for it.
Tolman and one of his graduate students, Charles Honzik, conducted a study that they argued was a convincing demonstration of latent learning (Tolman & Honzik, 1930). The study had three conditions: (1) a control group of rats allowed simply to wander through the maze with no reward; (2) a learning group, where rats were rewarded from the beginning for finding their way through the maze; and (3) the latent learning condition, where the rats were not rewarded until the 11th day of the experiment. As would be predicted by Hull and other neobehaviorists who saw learning as a matter of reward or reinforcement, the rats in the learning condition quickly reduced the number of errors (false directions in the maze) and the number of errors dropped daily. However, latent learning, that is, Tolman’s theory that learning occurs constantly and only needs the right conditions for it to be
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demonstrated, was supported by the behavior of the rats in the latent learning condition.
For these rats, the number of errors matched that of the control group for the first 10 days.
However, on the 11th day, when reward was introduced, the number of errors of these rats was dramatically reduced and quickly became fewer in number than those of the learning group. Tolman interpreted this as supportive of his theory that learning is purposive, or goal directed.
This work, and more like it, became the cen- ter of experimental psychology in the period between the wars. While the number of experi- mental psychologists was not large, it is accurate to state that work on conditions of learning or adaptation was central. If we look beyond the center, as we do next, we see that other significant bodies of psychological research and application emerged in this period.