Wednesday, August 6, 2008

The Neo-Behaviorists: Guthrie, Tolman, and Hull :

Edwin R. Guthrie (1886–1959), the “most starkly empiricist of all the neo-behaviorists” (J. A. Mills, 1998), defined mind as “a mode of behavior, namely, that behavior which changes with use or practice-behavior, in other words, that exhibits learning” (E. R. Guthrie, 1935/1960). The ability to learn, as C. Lloyd Morgan had suggested, characterized the possession of mind in living creatures. Guthrie’s theory of learning was deceptively simple: Learning occurs through the development of associations between stimuli and responses. These associations are formed by contiguity: “A combination of stimuli which has accompanied a movement will on its recurrence tend to be followed by that movement”. He rejected Thorndike’s laws of effect and of exercise, claiming instead that the apparently gradual nature of learning was a result of a series of one-trial situations in which movements, small muscle responses, rather than acts were learned in response to stimuli. The role of the consequences of responding, whether satisfying or annoying, was to change the stimulus situation, not to strengthen some unobservable bond between
stimulus and response. In contrast to E. R. Guthrie’s molecular approaches to learning, Edward Chace Tolman (1886–1959) offered a molar theory of the psychology of learning. For E. R. Guthrie and for J. B. Watson, descriptions of learned behavior were confined to descriptions of stimulus events and responses. Tolman, in contrast, proposed a theory that interpreted behavior in terms of “motive, purpose and determining tendency” (Tolman, 1922). For Tolman, cognitive events intervened between the antecedent stimuli and their behavioral consequences. Learning and performance were not synonymous (Innis, 1999; Kimble, 1985; Tolman & Honzik, 1930); performance was the observable behavior, while learning was the hypothesized state that accounted for the change in behavior. Tolman described the action of intervening variables on the functional relationship between the independent and dependent variables; that is, between the environmental stimuli and physiological state of the organism on the one side and the overt behavior on the other (Tolman, 1932; see also Innis, 1999; Kimble, 1985). The most important intervening variables were cognitions, defined as expectations about the relationship between signs, stimuli, and significates, rewards or goal objects (J. A. Mills, 1998; Smith, 1986). Tolman hypothesized the formation of “cognitive maps” or cognitive representations of the environment in rats learning a maze. These cognitive maps could be empirically demonstrated in maze experiments in which, for example, blocking a previously used route to a goal resulted in rats choosing the next shortest path to the goal (Tolman, Ritchie, & Kalish, 1946).
Clark Hull (1884–1952) proposed a formal logicodeductive theory of behavior: “In science an observed event is said to be explained when the proposition expressing it has been logically derived from a set of definitions and postulates coupled with certain observed conditions antecedent to the event” (Hull, 1943). Hull’s theoretical treatment of psychology consisted of a set of postulates and corollaries and their mathematical statements to enable quantitative predictions about behavior. Hull’s goal was to develop psychology as a natural science by demonstrating that behavioral phenomena obey universal, quantitative laws that can be stated by equations comparable to physical laws, “of the type governing the law of falling bodies” (Hull, 1950). Even centuries after Kant, Hull was striving to demonstrate that psychology could indeed become a science that met the same standards as the physical sciences. For example, Hull (1934a, 1934b) proposed that the serial position effect in learning a list of words (the phenomena that errors occur more frequently in learning and in the recall of words from the middle of a serial list) exemplifies the same general law that describes the pattern of errors made by rats learning a complex maze (more errors occur in the center of the maze than at the start and the finish). Hull’s research program was directed toward the discovery of such laws and the formulation of the equations that described them. His theory of behavior formulated theoretical
variables in operational terms, defined them by equations, and predicted experimental results. Experiments by Hull, Tolman, and their students were designed to provide crucial tests of predictions from their respective theories. For example, Hull’s theory hypothesized that learning occurred through reinforcement, defined in terms of the extent to which reinforcement reduced a motivational drive; Tolman, on the other hand, argued that reinforcement in this sense was unnecessary for learning (Tolman & Honzik, 1930). Resolution of such theoretical issues was difficult; moreover, the
precise predictions from Hull’s formal theory were frequently not confirmed, and criticism of the theory began to mount from a variety of sources, including Hull’s own students (J. A. Mills, 1998). Differences between the theories of Hull and Tolman came to seem less substantive and more a preference for particular terminology and the reification of intervening variables (Kendler, 1952).

The Radical Behaviorism of B. F. Skinner :

Burrhus Frederick Skinner (1904–1990) questioned whether theories of learning were necessary in view of what appeared to be fruitless theoretical tests (Skinner, 1950). He argued instead for a purely empirical description of behavior, eschewing any hypothetical or intervening nonobservable variable in his description of behavior, a position that he had established in his first major publication (Skinner, 1938). His manipulation of the contingency between an operant (emitted) behavior and a reinforcer constituted his program of research, carried out in the operant-conditioning chamber more popularly known as a “Skinner Box.” With rats and later pigeons as his experimental subjects, Skinner measured cumulative responses over elapsed time as a function of reinforcement schedules (Ferster & Skinner, 1957). Intervening variables, such as drive or motivation, were defined operationally in terms of number of hours of deprivation or percent of free-feeding body weight. The reports of experiments by Skinner and his followers, with few animals but a large number of responses, met with rejection from editors whose definition of an experiment required a research design comparing experimental and control groups with a statistical test of the significance of the difference between them. The result was the establishment of the Journal for the Experimental Analysis of Behavior in 1958 (Krantz, 1972). Skinner’s approach to behavior extended to the development and use of language (Skinner, 1957) and to the technology of teaching (Skinner, 1968).

The Rise of Cognitive Psychology: Mentalism Revisited :

The experiments engendered by the debates among the different approaches to learning and behavior continued to dominate the literature of experimental psychology at midcentury. However, the traditional methods and research topics of the psychological laboratory also flourished; although the era of the schools had ended, they left a legacy of influence on the research conducted within psychology. Introspection as a source of psychological data lost its primacy with the end of structuralism; introspective reports resumed their more limited role in assessing the quality and/or intensity of sensory experience in psychophysical experiments. Articles reporting on experiments on perception, stimulated in part by gestalt psychology’s emphasis upon perceptual organization, continued to appear in psychological journals, together with studies of the higher mental processes of thinking and problem solving (e.g., Wertheimer, 1959). Functional psychology, more of an attitude than a systematic position, characterized American psychology generally and fostered experiments on serial list and paired associate learning and the interference theory of forgetting, continuing the research tradition emanating from the laboratories of Ebbinghaus and G. E. Müller (McGeoch, 1942). Although research on higher mental processes in animals had not been entirely neglected (Dewsbury, 2000), behaviorism left a legacy of animal research that focused on stimulus-response interpretations of the results of maze learning studies, classical conditioning experiments, and, increasingly, of behavior in operant conditioning chambers. Psychology redefined itself from the science of mind to the science of behavior. References to mind or mental processes were found only infrequently in textbooks and journals. The molecular, elemental, and mechanistic analyses of behaviorism, emphasizing peripheral sensory-motor relations,
were not limited to research on learning. Child psychology, for example, was strongly influenced by studies of the conditioned reflex (e.g., Mateer, 1918) and Watson’s admitted premature claim that, given a dozen healthy infants, he could make of them anything he chose (J. B. Watson, 1924). Emphasis on the study of sensory-motor and nervous-system development in young children led to an emphasis on developmental
norms that were postulated to follow relatively fixed maturational principles (e.g., Gesell & Ilg, 1946). These principles and norms were challenged by research that combined behavioral and maturational approaches in examining motor development in children (e.g., McGraw, 1935; 1943). In the decades of the 1950s and 1960s, the language and models that stimulated psychological research began to change. Explanations of behavior derived from experiments on maze learning and classical and operant-conditioning research came under attack from those studying more complex
behavior patterns (e.g., Harlow, 1953). Rote learning of serial lists and verbal paired associates were acknowledged to represent only a limited domain of human learning (Melton, 1956). Information theory, developed during World War II as a tool for measuring the capacity of humans as processors and transmitters of information, provided a new measure of human performance and implied capacities for making judgments and choices (Attneave, 1959). Information theory offered fresh interpretations of choice reactiontime experiments (e.g., Hick, 1952) and the limits of human attention and immediate memory (Miller, 1956). Discussions of human capacities to reduce, transmit, or create information renewed interest in cognitive capacities of decision making and problem solving that suggested analogies to the recently developed technology of the computer. Interest in cognitive development revitalized child psychology in moving from a focus on sensory-motor development
to a focus on thinking, the formation of concepts, and the child’s understanding of the world. The theories of Jean Piaget (1896–1980) that describe the development of language and cognition in childhood had appeared in the 1920s and 1930s in Europe (e.g., Piaget, 1929) but had an impact in the United States only decades later (Flavell, 1963). Experimental research that explored cognitive and social development
in children came to dominate the field of developmental psychology, no longer simply child psychology but soon to cover the life span. This shift in emphasis in the study of human development paralleled changes in research on adults and on animals.
Psychologists appeared to be less self-consciously concerned with the status of psychology as a science and more concerned with the kind of science psychology was to be. The behavioral view of a largely passive organism whose mechanical behavior was governed by environmental events became an increasingly less satisfactory model. Calls for a humanistic, rather than a mechanistic, science of psychology (Giorgi,
1970; Maslow, 1966) called for a view of human beings as actively engaged with the environment, thinking and deciding rather than simply responding to external events. The results of Pavlovian conditioning experiments began to be interpreted in terms of cognitive events (e.g., Rescorla, 1966) and signaled the increasing willingness to consider the role of mental processes that determined behavior in both humans and animals. The journals Cognitive Psychology (1970) and Memory and Cognition (1973) were founded to provide an outlet to the burgeoning research in human memory that was
less characteristic of traditional associationistic theories (Warren, 1921; Robinson, 1932/1964) and more influenced by analogies to computers and conceptions of information processing. Topics of the older mentalistic psychology, such as attention, concept formation, and thinking, became more prominent in psychological research. The term mind, banished from the psychological lexicon in the heyday of behavioral theories, began to reappear in textbooks and, more significantly, in developing theories of human and animal cognitive capacities. The magnitude of the shift in research agendas and theoretical constructs suggested that psychology
had undergone a revolutionary change, while others regarded the shift as part of the normal historical development of the discipline (Leahey, 1992). Nevertheless, these developments in scientific psychology represent the continuing vitality of the discipline as psychologists address traditional problems of mind and behavior in forging the science of psychology. These efforts inform the content of the volumes and chapters that follow and properly belong to contemporary psychology.

Inferential statistics was unknown until the twentieth century:

Student’s “t” test for comparing mean scores from two groups appeared in 1908. Analysis of variance tests were devised in the 1920s (Smith et al., 2000) but did not become a common part of psychological research designs until the 1930s (Rucci & Tweney, 1980). With the publication of his Experimental Psychology (1938), R. S. Woodworth “introduced a clear distinction between experimental and correlational research” (Winston, 1990). The critical distinction made between the two kinds of research was that only in experimental work could the cause of behavior be determined by manipulation of an independent variable; the definition “provided one powerful rationale for the animal research of the thirties, forties, and fifties” (Winston, 1990) because manipulations of “causal” variables in animal research provided fewer ethical or practical problems than research with humans. The search for causes of behavior and the theoretical models of learning embodied this definition of the psychological experiment as the means of testing hypotheses. This model of the experiment helped to establish prescriptions for the use of t-tests and analyses of variance as the statistical treatments of choice for the results of experiments, while correlational techniques and regression analyses were utilized by those interested in
individual differences. The methodology of research and standards for analyzing and reporting results of experiments in keeping with psychology’s status as a science is reflected in the standardization of the reports of experiments and the definition of the experiment. The emphasis on hypothesis testing and statistical analyses of comparisons between control and experimental group performance that later came to dominate experimental design and instructions to authors preparing manuscripts reflected the success of Woodworth’s definition of what constituted an experiment in psychology.

Data Treatment and Research Design

Early published reports of “even narrowly focused laboratory studies conducted with small samples were capable of generating reams of detailed data; readers of journal reports were sometimes confronted with tables of data that ran on for pages” (Smith, Best, Cylke, & Stubbs, 2000). Summary data were presented not only in tables but also in graphic form. Graphs were a common form of data summary in turn-of-the-century scientific reports [the forgetting curve of Ebbinghaus (1885) and the learning curve of Thorndike (1898) were two influential examples of graphic representation]. In addition, graphs helped to pave the way for the later development of correlation and regression analyses (Smith et al., 2000). In attempting to assess the degree of relation between physical and mental characteristics to each other, Francis Galton (1822–1911) used scatter plots in which one set of scores was arranged as a function of another set, such as the height and weight measures of a group of individuals. From such graphic plots evolved the regression line, the steepness of which reflected the degree of relation between two variables, and, in the hands of Karl Pearson (1857–1936), developed into the mathematical technique of correlating variables and measuring the degree of their relationship by the coefficient of correlation (Fancher, 1996). The development of these statistical methods became critical to the assessment of individual differences and the use of tests in psychology. Other statistical procedures were employed to assess comparisons between different groups of individuals. Galton’s research, for example, on the efficacy of prayer asked “whether those who pray attain their objects more frequently than those who do not pray, but who live in all other respects under similar conditions” (Galton, 1872, as cited by Dehue, 2000). A control group was employed in educational research to assess the effects of transfer of training (the influence of practice in one task on performance in another), and, despite arguments over whether participants should be assigned to an experimental or control group at random or by matching individuals, the use of control groups in psychological experiments became an integral part of research design (Dehue, 1997). The comparison of control and experimental group performances led to the use of statistical procedures for testing the significance of any differences that might be obtained.

Defining Psychology and Its Methods

Changes in the psychological experiment in apparatus and methods and the shift in roles of observer and experimenter occurred amid debate over the subject matter of psychology and the methods appropriate to it. The growth in the range of subject matter under experimental investigation and in the methods employed in the study of psychology reflected James McKeen Cattell’s definition of psychology’s subject matter as anything that a psychologist is interested in, as a psychologist (Cattell, 1947a). The experimental psychology that arose in North America resembled the research practices of G. E. Müller more than those of Wilhelm Wundt in the range of topics addressed in the laboratory and the apparatus and methods that were employed. The psychology that evolved in college and university departments of philosophy and, as the century matured, in independent
departments of psychology reflected the functional spirit of the mental philosophers and the influence of the theory of evolution. Mental philosophy had attempted to describe how mind worked, how its cognitive and conative processes operated to produce volitional acts. American psychologists, imbued with the spirit of evolutionary theory, were focused on the
utility of mind and consciousness in the adaptation of species and individuals to the environment. This concern with function (what is mind for? what is its function? —presumably, to aid adaptation) was coupled with other aspects of function, namely, how mind works (how does it function?) and on what mind depends (of what is mind a function? how complex must a nervous system be before mind becomes possible?). These implicit and broad concerns for mental function in psychology were made more explicit and embodied in a selfconscious school of psychology by James Rowland Angell (1869–1949) in response to the programmatic statement of E. B. Titchener (1867–1927), who advocated a structural
psychology. These schools of thought were but two among general systematic positions that competed for dominance in psychology (Heidbreder, 1933; Murchison, 1926, 1930;
Woodworth, 1948).

Structural and Functional Psychologies

Oswald Külpe’s method of systematic introspection had a very strong proponent in Edward Bradford Titchener at Cornell University. Titchener had become interested in
Wundt’s psychology while studying philosophy and physiology at Oxford University. He translated the third edition of Wundt’s Gründzüge into English and, when he could find no one in England with whom to study the new science, went to Leipzig to complete his doctorate with Wundt in 1892. English universities were unreceptive to the new psychology; Titchener accepted a professorship at Cornell University,
where he remained until his death in 1927. Titchener presented himself as Wundt’s representative in North America, but his psychology was not Wundt’s voluntarism
(Leahey, 1981; Danziger, 1990). Titchener’s view of mind was influenced by the English philosophy of John Locke and his heirs that he had studied at Oxford. The British philosophers viewed mind as a recipient of stimulation: Mental content was whatever had entered mind through the senses. The purpose of the study of mind was to understand how complex mental experience and function could arise from combinations of these elements. Laws of association, by which elements combined, played a significant role in understanding how mind grew from sensory elements. Similarly, mind was, for Titchener, composed of elements that he identified as sensations, images, and affections. Sensation was the primary experience resulting from stimulation of the senses, images were complex representations that carried thought, and feelings were the elements of which emotions were comprised. Through the direct systematic introspection of consciousness under laboratory conditions, Titchener pursued three goals: the reduction of conscious experience to its basic elements, determining how the elements were connected to form complex perceptions, and
identifying the underlying physiological processes. The first of these goals provided the primary focus of research at the Cornell laboratory, as the elements were themselves analyzed for their attributes (which, in a later version of the system,
became the new elements of consciousness; see Evans, 1972). Pursuit of the other goals was secondary because they depended upon the successful completion of the first. The subject of psychology, Titchener argued, was the understanding of the human, adult, normal, generalized mind through the use of introspection; only after psychology had completed that task could the nonhuman, child, abnormal, or
individual mind be understood. For Titchener, psychology needed to emulate physics, with its pursuit of the analysis of matter into the smaller units of which it was composed. Titchener stood for rigorous experimental pursuit of the elements of mind, pursued for their own sake and not for any potential application. He disparaged “functional psychology” as essentially the “mind in use” approach of the older, discarded philosophical psychology. An early response to Titchener’s postulates for his structural psychology came from John Dewey (1859–1952), chair of the Department of Philosophy, which subsumed psychology and pedagogy, at the University of Chicago. Dewey perceived that the new method of laboratory experiment would free the older barren mental philosophy from the theological and philosophical constraints of its past and open the way for a useful psychology that would help resolve problems of the
asylum, the classroom, and other practical affairs (Dewey,1884). He facilitated the establishment of a laboratory at the University of Michigan before moving to Chicago. In 1896, Dewey argued against reductionist approaches to the study of consciousness and for a functional analysis and understanding of mind (Dewey, 1896). A functional approach to mind was embedded in the nineteenth century mental philosophy taught in American colleges (Fuchs, 2000a) and its development at the University of Chicago was influenced by pre-Chicago Associations among Dewey and others (Raphelson,1973).
James R. Angell, a graduate of the University of Michigan and a student of psychology there, built on Dewey’s approach in his presidential address to the American Psychological Association in 1906 (Angell, 1907), in his successful textbooks
(e.g., Angell, 1905), and from his position as Professor of Psychology at the University of Chicago. Functional psychology dealt not with mental elements as its primary focus but with mental operations; the role of consciousness in helping to adapt an organism to its environment involved psychology in a concern for mind and body relationships (Angell, 1907). Functionalism was interested in the uses of consciousness and its role in guiding behavior; it was profoundly practical and reformist. Psychology and other social sciences were useful to a variety of educational and social reforms promoted during the progressive era (Fitzpatrick,
1990; Milar, 1999). Angell’s approach to psychology encompassed the broad range of interests and methods that had developed in psychology since 1879 and reflected the influence that evolutionary theory exerted on psychology in the United States.
The science of mind was pursued in the laboratory; mind was its subject matter, and many methods were available for its study. Psychophysical experiments, research on the connections between physiology, especially the nervous system, and mental processes, and direct observation of others, including children and animals, provided data that could supplement the results of introspection under laboratory conditions
(Angell, 1905). The use of a variety of methods would, in Angell’s view, supplement the results of the direct observations of mind that introspection provides. Functional psychology was interested in how mind worked (i.e., how it functioned) and on its functional relation to the physiological substrate (i.e., on what did mind depend) and its purpose (i.e., its use or function) and was less concerned the content of mind. Mary Whiton Calkins (1863–1930) attempted to reconcile the differences between the structural and functional psychologies by proposing a psychology of the self that possesses both conscious contents and mental functions.
Calkins had begun her study of psychology unofficially at Harvard with William James and Josiah Royce in 1890; Clark University professor Edmund Sanford tutored Calkins privately in experimental psychology. In 1891, Calkins established the first psychological laboratory at a women’s college at Wellesley College, one of the first 12 laboratories in the United States (Furumoto, 1980). She developed the pairedassociate technique for the study of verbal learning and memory and published papers on her research and on experiments conducted with students in the Wellesley laboratory (Calkins, 1894a, 1894b). She pursued further study in psychology with Hugo
Münsterberg at Harvard, but not as an officially registered student. Münsterberg petitioned Harvard’s president to allow Calkins to be admitted as a candidate for the PhD, but his request was refused. In May 1895, after an unauthorized examination,
the following communication was forwarded to The Harvard Corporation: “At the examination, held . . . before Professors Palmer, James, Royce, Münsteberg, Harris, and Dr. Santayana it was unanimously voted that Miss Calkins satisfied all the customary requirements for the degree” (cited in Furumoto, 1980). Again, the PhD was denied (Harvard refused to grant the doctoral degree to a woman until 1963). In
1902, four women who had completed graduate study at Harvard were offered PhD degrees from Radcliffe College. Radcliffe, established in 1894, offered almost exclusively
undergraduate courses; women who completed graduate work did so at Harvard University. Calkins refused the Radcliffe degree, seeing it as a symbol of Harvard’s refusal to admit women on an equal footing with men (Scarborough & Furumoto, 1987). In 1905, Mary Whiton Calkins became the first woman elected to the presidency of theAmerican Psychological Association. By 1905, the functional point of view had become the dominant view in American psychology (Leahey, 1992). For his part, Angell claimed that functionalism could easily contain Calkins’s “Self Psychology,” “were it not for her extreme scientific conservatism in refusing to allow the self to have a
body, save as a kind of conventional biological ornament” (Angell, 1907). Calkins, and Titchener, did not reject the pursuit of identifying the physiological substrates of mental content and processes but placed that pursuit at a lower priority to the study of mind more directly. Indeed, Calkins extended the use of introspection to the study of abnormal experiences of the normal self and included the study by comparative means of abnormal individuals (Calkins, 1901,1919) among the range of topics to be studied in the new psychology. In these psychologies, introspection continued to serve as a method for the direct examination of conscious experience,
but problems arose when introspective reports from different laboratories contradicted each other. Doubts about the capacity of introspection to serve as a scientific method were brought forcefully into focus by the “imageless thought” controversy. Titchener’s psychology proposed that images were the carrier of thoughts, and introspective observations carried out in his laboratory supported his position. Oswald Külpe and his colleagues at the University of Würzburg, however,
failed to observe images in their studies of thought processes and concluded that thinking was carried out by “imageless thoughts.” How could introspection, as a method, reconcile incompatible results when conscious experience was private
and not open to public inspection? Supporters of introspection as the primary method of scientific psychology added more instructions in an attempt to improve the method (English, 1921) while others advocated its more limited use among other psychological methods (Angell, 1905; Dodge, 1912). The question of whether introspective
analysis could indeed serve as a scientific method producing reliable data was present at the start of psychology’s history as a science. Introspective observations were reliable within limits: A wavelength of light at a given frequency was reported to evoke the same color sensation in all observers of normal vision. The question lay in the capability of introspection to go beyond such limited observations in the
search for elements of mind. Meanwhile other research traditions arose.

Child Study

At Clark University, G. Stanley Hall established a graduate program in psychology that attracted students in numbers sufficient to make Clark a leader in psychology after its opening in 1889. In its first decade, 30 of the 54 doctorates in psychology awarded in the period were earned at Clark (White, 1992). In his laboratory of psychology, Hall fostered the experimental methods that he had learned in Germany and appointed E. C. Sanford (1859–1924) to supervise the experimental work. Hall’s primary interest lay in developmental psychology; his recapitulation theory of development reflected the nineteenth-century view that the course of development of an individual parallels the stages of human evolution (Richards, 1992). Thus, “every child, from the moment of conception to maturity, recapitulates, . . . every stage of development through which the human race from its lowest animal beginnings has passed” (Hall, 1923, p. 380). Although the theory was later discredited, it served a useful purpose in stimulating research. In 1891, Hall introduced the use of child-study questionnaires, the “Clark method” (Danziger, 1985, 1990). Questionnaires were designed to investigate “(a) simple automatisms, instincts, and attitudes, (b) the small child’s activities and feelings, (c) control of emotions and will, (d) development of the higher faculties, (e) individual differences, (f) school processes and practices, and (g) church processes and practices” (White, 1992, p. 29). Much of Hall’s research on childhood and that of his students culminated in his two-volume Adolescence (1904). Child psychology was not, however, uniquely the property of Hall and his university. James Mark Baldwin’s Mental Development in the Child and the Race (1895) and its companion volume, Social and Ethical interpretations of Mental Development (1897), were attempts to bring a genetic account of development into the new psychology and “to bridge the gap between the study of social institutions (i.e., sociology) and the study of individual functioning (i.e., psychology)” (Cairns, 1992). Baldwin’s contributions were fleeting, for many reasons (see Cairns, 1992), among which was that his theoretical formulations were out of step with the heavy empirical emphasis prevalent in psychology at the time. Similarly, Hall’s influence was limited by the critical attack from those closely tied to laboratory investigations that his questionnaire research was methodologically weak. Nevertheless, Hall and Baldwin made the psychology of child development and the methods appropriate to its study part of the new psychology.

Individual Differences

Although recapitulation theory influenced Hall’s approach to child study, the direct influence of evolutionary theory on child study was slight (Charlesworth, 1992). However, the theory of evolution strongly influenced the study of individual differences. For natural selection to serve as the primary mechanism of evolution, variation in species populations was necessary for the selection of traits that were the basis for adaptation and survival within different and changing environments. Francis Galton, a cousin of Darwin, contributed to the history of psychology through his measures of physical and mental characteristics of individuals who visited his Anthropometric Laboratory. The measures of physical characteristics such as head size, arm length, height and weight, and performance characteristics such as reaction time and sensory acuity, used by Galton and adapted from the tasks of the psychological laboratories, were employed as mental tests of intelligence. Head size, for example was (falsely) assumed to indicate brain size and intellectual capacity, and speed of responses and visual acuity were assumed to indicate adaptability and survival capability. The term intelligence came to be used to designate differences among individuals in their capacity for such complex behaviors as reasoning and problem solving rather than to denote differences among species in adapting to the
environment, the more common use of the term in the nineteenth century.
James McKeen Cattell, who had studied with Hall at Johns Hopkins before earning his PhD with Wundt, pursued his interest in individual variation, labeled “ganz
Amerikanisch” by Wundt (Boring, 1950), while in Francis Galton’s London laboratory. Cattell returned to establish a laboratory at Columbia University and adapted laboratory tasks familiar to him from both Leipzig and London to identify and measure differences in reaction time, sensory sensitivity, time estimation, and memory span in undergraduate students (Sokal, 1987; Tuddenham, 1962). Like Galton, he theorized that such tasks as reaction time, sensory acuity, memory, and apprehension spans would reveal an individual’s intellectual abilities. His attempt to relate scores on
these tasks to academic performance demonstrated little relationship between the performance scores on the laboratory tests to academic performance in courses at Columbia (Sokal, 1987) but nevertheless represents an early effort to measure the intelligence of individuals. Assessing individual differences among human beings did
not necessarily result in appropriate conclusions about the consequences of evolution because of the importance of social and cultural factors in determining differences among individuals. For example, Galton’s study of sex differences in psychological characteristics reflected social and cultural views of the capabilities and proper roles for women and men rather than differences that could be attributed to evolutionary forces. This bias was common at the time and addressed by the research of one of James R. Angell’s graduate students, Helen Bradford Thompson. Her dissertation, completed at the University of Chicago in 1900 and later published
as The Mental Traits of Sex (1903), was the first systematic, experimental investigation of sex differences in motor ability, sensations, intellect, and affect. Careful, detailed analysis of the results led to her conclusion that “the
psychological differences of sex seem to be largely due, not to difference of average capacity, nor to difference in type of mental activity, but to differences in the social influences brought to bear on the developing individual from early infancy to adult years”. Hall, too, had employed evolutionary arguments to bolster stereotyped ideas about the psychological nature and proper roles of men and women. His rather unflattering assessment of women’s abilities attracted little argument from American
male psychologists of the time (see Diehl, 1986; Shields, 1975) and played a role in denying opportunities for graduate study and professional employment for women (Milar, 2000). In 1910, Helen Thompon, writing under her married name, Helen ThompsonWoolley, reviewed the literature on sex differences and asserted, “There is perhaps no field aspiring to be scientific where flagrant personal bias, logic martyred in the cause of supporting a prejudice, unfounded assertions, and even sentimental rot and drivel, have run riot to such an extent as here” (Woolley, 1910, p. 340). Similar conclusions could have been drawn about comparisons among races
begun before the development of evolutionary theory. These comparisons had also served to justify a hierarchy that placed Caucasians in a superior position, and later studies under the aegis of evolutionary theory continued to be carried out
and interpreted in terms of long-held cultural biases (see R. Guthrie, 1998).
Influenced by Cattell and Hall’s child study movement, Lightner Witmer (1867–1956), attempted to put performance on laboratory tasks to practical use in the new discipline that he labeled “Clinical Psychology” (McReynolds, 1996). The apparatus and methods of the laboratory experiment were successful in assessing differences among individuals but proved to be of little value for Witmer’s purposes (McReynolds, 1996). The failure of laboratory tasks for these applied ends led, in the case of intelligence testing, to the refinement and development of tests modeled on those of
Alfred Binet and, in Witmer’s case, to the search for more suitable methods for assisting individuals. These efforts also led to attempts to identify characteristics of individuals that, like intelligence, were both measurable and offered promise
of relevance, such as personality assessment (Allport, 1937), attitude and aptitude measures, and clinical diagnostic tests (Gregory, 1992). For many psychologists, individual differences were a distraction to the understanding of the general principles governing mind, while for others, the understanding of the individual mind was the most interesting task for psychology. The difference in emphasis and the somewhat separate paths of development of the two pursuits within psychology
came to be seen as the two disciplines of scientific psychology (Cronbach, 1957).

The Study of Nonhumans: Animal Psychology

Darwin’s theory of evolution had raised questions about the adaptive utility of consciousness; the relation of human to animal ancestry had raised issues of whether there are instincts in humans and whether animals exhibited human intellectual
capacities and consciousness in adapting to changed or changing environments. Learning capacities and consciousness seemed in turn to depend upon the complexity of the nervous system: “If there is a Comparative Anatomy there is also a Comparative Psychology” (Chadbourne, 1872). George J. Romanes (1848–1894), a devoted younger friend of the aging Darwin, explored these concerns by collecting anecdotes of wild and domestic animals that provided evidence of capacities for reasoning and problem solving analogous to those exhibited by humans. As part of an animal’s intelligent
adaptation to an environment, he sought evidence of reason, stimulus situation, without the mediation of ideas. The bond between response and situation was strengthened if the response was followed by a satisfying outcome, or weakened if it was followed by an unsatisfactory consequence. This statement constituted Thorndike’s “law of effect.” He also held that bonds between the situation and response became
strengthened through exercise and weakened by disuse: the “law of exercise” (Thorndike, 1913). Thorndike claimed that these two laws, together with the animal’s “readiness” to respond in the situation, accounted for most of animal learning
(Thorndike, 1913). In his early work in comparative psychology, Thorndike emphasized a discontinuity between animals and humans. By 1911, however, he reversed his position to emphasize instead the universality of the law of effect and other laws of learning (Bruce, 1997). Although the thrust of Thorndike’s laws was to specify
regular relations between a situation and the responses that it may come to evoke, without any attempt to assess the content of the mind of the responding animal, comparative psychology did not immediately follow his lead. Concerns for the
adaptive value of consciousness in humans and animals continued to be addressed in the early decades of the twentieth century (e.g., Judd, 1910). Identifying the levels of complexity of nervous systems that would justify inferences about the nature of animal consciousness and capacity for intelligent behavior (e.g., Yerkes, 1905) is best exemplified by what has sometimes been called the first textbook in comparative psychology, Margaret Washburn’s The Animal Mind (1908) (Jaynes, 1968, cited in Furumoto & Scarborough, 1987). Margaret Floy Washburn (1871–1939), the first woman to
earn a PhD in psychology and the second woman president of the American Psychological Association (1921), summarized and organized the scattered literature on animal psychology, provided a history of the movement, and offered an extensive discussion of methodology for research with animals (Washburn, 1908; Goodman, 1980). E. B. Titchener’s first doctoral student, Washburn had applied to study psychology with James McKeen Cattell at Columbia, but Columbia, like Harvard and the Johns Hopkins University, permitted women to attend classes only unofficially as “hearers.” Cattell, however, encouraged her to apply to Cornell, where she completed her degree in 1894. Areport of her Cornell dissertation on the effects of visual imagery on tactile sensitivity was one of the few studies published in Wundt’s Philosophische
Studien that had not been completed at Leipzig. Washburn sought to understand the animal’s conscious experience in an approach to comparative psychology characterized
as “subjective, inferential and rigorously logical” (Goodman, 1980, p. 75). Washburn was influenced by the research and writing of both Morgan and Thorndike; like
Thorndike, she advocated the use of objective and rigorous experimental procedures, but, like Morgan, she persisted in her view that animals possessed a consciousness that psychology was obliged to define and characterize (Washburn, 1917, 1926, 1936). To carry out its responsibility, psychology needed to adopt objective and rigorous experimental procedures. Despite the growing emphasis on the sufficiency of behavioral data and the emphatic rejection of mind and consciousness as the only legitimate subject matter for a scientific psychology, as Thorndike advocated, Washburn held to her position (Goodman, 1980). which he defined as the conscious knowledge of the relation of the means to an end. In addition, Romanes described
patterns of instinctive responses that occurred without a conscious awareness of the end to which they were adapted (Romanes, 1892). Romanes’ research methods and anthropomorphic conclusions about the capacities of animals were criticized by
C. Lloyd Morgan (1852–1936) for relying on unsubstantiated anecdotes and weak analogical reasoning. Morgan emphasized the importance of observation and encouraged parsimony in interpreting observations of animal behavior (Morgan, 1890–1891, 1896). His caution in this regard came to be known as Morgan’s Canon: “In no case should an animal’s activity be interpreted in terms of higher psychological processes if it could be interpreted in terms of processes standing lower in the scale of psychological evolution” (R. I. Watson & Evans, 1991, p. 329). Morgan provided a necessary methodological corrective to enthusiastic but unscientific fact gathering by emphasizing both care in making observations and caution in interpreting them.
Morgan employed experimental methods and observation in naturalistic settings and hypothesized that animals learned through association of ideas, in accord with the philosophical tradition of associationism (Warren, 1921) that described how the human mind operated (Cumming, 1999; Furumoto & Scarborough, 1987). Although we can know our own consciousness, we can only infer consciousness in others, including animals; for Morgan, the criterion for inferring consciousness in animals is “circumstantial evidence that the animal . . . profits by experience” (Morgan, 1900). In this way, Morgan stimulated interest in the study of learning, not only as an adaptation to the environment, but also as the criterion for inferring animal consciousness or mind.
At Clark, research in animal behavior attempted to describe the animal mind and to study the development of the nervous system. The former research was represented by Willard Small’s use of the maze to study the mental processes of the white rat involved in learning (Small, 1900, 1901). The latter research was represented by H. H. Donaldson, who attempted to describe the growth of the nervous system in rats and humans (e.g., Donaldson, 1908). One purpose of this research by Donaldson and Small was to relate the complexities of the nervous system between species and between individuals in the same species to differences in behavioral and mental abilities.
Small employed a version of the Hampton Court maze (Munn, 1950) that later gave rise to the many variations (e.g., the T-maze, multiple T-maze, and the straight alley maze) that became standard laboratory equipment for the study of learning and the testing of learning theories of the 1930s through the 1950s. Donaldson and Swiss American psychiatrist Adolf Meyer are credited with helping to establish the albino rat as the dominant laboratory animal in American psychological laboratories for many decades (Logan, 1999). The work at Clark proceeded in the spirit exemplified by
Morgan and by E. L. Thorndike (1874–1949), who, in 1898, had insisted that experiment must be substituted for observation and the collection of anecdotes” (Thorndike, 1898). Thorndike’s dissertation, Animal Intelligence (1898), signaled a major shift from a subjective, introspective, anecdotal study of animals to an objective, quantitative experimental approach with an emphasis on learning (Galef,
1998; Stam & Kalmanovitch, 1998). Thorndike’s emphasis on controlled observation was welcomed by Morgan, who advanced “the hope that comparative psychology has passed
from the anecdote stage to the higher plane of verifiable observation, and that it is rising to the dignity of science” (Morgan, 1898). Thorndike had pursued graduate study at Harvard with an investigation of the behavior of chickens, until the protests of his landlady forced him to move his chicken experiments to the basement of William James’s house (Dewsbury, 1998; Thorndike, 1936). Thorndike subsequently took his two “most educated chickens” to study the inheritance of acquired traits at Columbia University with James McKeen Cattell. The topic did not prove very fruitful, and Thorndike chose instead to examine the performance of cats and small dogs in puzzle boxes. The choice of puzzle boxes was influenced by the work of Romanes and Morgan, who had described dogs and cats learning to open garden gates through trial and error (Morgan, 1900). Thorndike’s boxes were designed to permit observation of animals’ attempts to escape from the box to reach food (Burnham, 1972). Various
boxes required manipulation of levers, pulling of loops, or combinations of responses to escape (Chance, 1999; Galef, 1998). Thorndike recorded and graphed the time taken to escape from the box as a function of the number of trials. He interpreted the gradual decline of the curve describing the time taken to escape from the box revealed by the graph to mean that learning proceeded gradually, through trial and
error. Responses that resulted in escape from the puzzle box appeared to be selected from random movements, in a manner analogous to the process of evolutionary selection. Thorndike insisted that responses were made directly to the stimulus situation, without the mediation of ideas. The bond between response and situation was strengthened if the response was followed by a satisfying outcome, or weakened
if it was followed by an unsatisfactory consequence. This statement constituted Thorndike’s “law of effect.” He also held that bonds between the situation and response became strengthened through exercise and weakened by disuse: the
“law of exercise” (Thorndike, 1913). Thorndike claimed that these two laws, together with the animal’s “readiness” to respond in the situation, accounted for most of animal learning (Thorndike, 1913). In his early work in comparative psychology, Thorndike emphasized a discontinuity between animals and humans. By 1911, however, he reversed his position to emphasize instead the universality of the law of effect and other laws of learning (Bruce, 1997). Although the thrust of Thorndike’s laws was to specify regular relations between a situation and the responses that it may come to evoke, without any attempt to assess the content of the mind of the responding animal, comparative psychology did not immediately follow his lead. Concerns for the
adaptive value of consciousness in humans and animals continued to be addressed in the early decades of the twentieth century (e.g., Judd, 1910). Identifying the levels of complexity of nervous systems that would justify inferences about the nature of animal consciousness and capacity for intelligent behavior (e.g., Yerkes, 1905) is best exemplified by what has sometimes been called the first textbook in comparative psychology, Margaret Washburn’s The Animal Mind (1908)(Jaynes, 1968, cited in Furumoto & Scarborough, 1987). Margaret Floy Washburn (1871–1939), the first woman to
earn a PhD in psychology and the second woman president of the American Psychological Association (1921), summarized and organized the scattered literature on animal psychology, provided a history of the movement, and offered an extensive discussion of methodology for research with animals (Washburn, 1908; Goodman, 1980). E. B. Titchener’s first doctoral student, Washburn had applied to study psychology with James McKeen Cattell at Columbia, but Columbia, like Harvard and the Johns Hopkins University, permitted women to attend classes only unofficially as “hearers.” Cattell, however, encouraged her to apply to Cornell, where she completed her degree in 1894. Areport of her Cornell dissertation on the effects of visual imagery on tactile sensitivity was one of the few studies published in Wundt’s Philosophische
Studien that had not been completed at Leipzig. Washburn sought to understand the animal’s conscious experience in an approach to comparative psychology characterized
as “subjective, inferential and rigorously logical” (Goodman, 1980, p. 75). Washburn was influenced by the research and writing of both Morgan and Thorndike; like Thorndike, she advocated the use of objective and rigorous experimental procedures, but, like Morgan, she persisted in her view that animals possessed a consciousness that psychology was obliged to define and characterize (Washburn, 1917, 1926, 1936). To carry out its responsibility, psychology needed to adopt objective and rigorous experimental procedures. Despite the growing emphasis on the sufficiency of
behavioral data and the emphatic rejection of mind and consciousness as the only legitimate subject matter for a scientific psychology, as Thorndike advocated, Washburn held to her position (Goodman, 1980).

Behaviorism

Animal psychology had drawn attention to the importance of behavior as a clue to mind, but inferences from behavior about animal consciousness were part of the expected interpretations of experimental results. But the focus of study was changing: “There is unquestionably a widespread movement on foot in which interest is centered on the results of conscious process, rather than in the processes themselves. This is peculiarly true in animal psychology; it is only less true in
human psychology. In these cases interest [is] in what may for lack of a better term be called ‘behavior’; and the analysis of consciousness is primarily justified by the light it throws on behavior, rather than vice versa” (Angell, 1911). The proposal that psychology reject its traditional definition as the science of mind and consciousness and redefine itself as a science of behavior came from John B. Watson
(1913). Watson arrived at the University of Chicago in 1900 to begin graduate work following an undergraduate degree in philosophy and psychology from Furman University (Harris, 1999; O’Donnell, 1985). H. H. Donaldson, who had moved to the University of Chicago from Clark University, brought with him his research program that investigated the relation between the development of the nervous system and the
behavior of the rat. Animal laboratories were few; in 1909, only about six laboratories were actively engaged in animal research (O’Donnell, 1985). For his dissertation, Watson chose to investigate the neurological correlates of problem
solving in the white rat and carried out additional experiments with rats to determine which sensory modalities were necessary for learning a maze by systematically eliminating one modality at a time. He removed the eyes, tympanic membrane, olfactory bulbs, and whiskers and anesthetized the feet of rats and discovered that the animals seemed to use kinesthetic feedback to reach the goal box (Carr & Watson, 1908; Goodwin, 1999; J. B. Watson, 1907). Watson’s first report of
these experiments at the annual meeting of the APA held in December 1906 in conjunction with the American Association for the Advancement of Science (AAAS) led to an outcry by antivivisectionists. He was publicly defended by Angell and by then APA president James Mark Baldwin (Dewsbury, 1990). Watson had become disenchanted with the language of consciousness and mind, with the method of introspection,
and was increasingly concerned about the status of animal research in psychology. Writing to fellow comparative psychologist Robert Mearns Yerkes in 1910, Watson expressed his identity problems: “I am a physiologist and I go so far as to say that I would remodel psychology as we now have it (human) and reconstruct our attitude with reference to the whole matter of consciousness. I don’t believe the psychologist
is studying consciousness any more than we are” (Watson, 1910, cited in J. A. Mills, 1998). In a series of lectures given at Columbia University in December 1912, Watson laid out his discomfort with a psychology of consciousness and proposed a psychology of behavior to take its place: “Psychology as the behaviorist views it . . . is a purely objective experimental branch of natural science. Its theoretical goal is the prediction and control of behavior. Introspection forms no essential part of its methods, nor is the scientific value of its data dependent on the readiness with which they lend themselves to interpretation in terms of consciousness” (Watson, 1913). Although this socalled “Behaviorist Manifesto” did not produce a revolution
in psychology (Leahey, 1992; Samelson, 1981), it did help to raise the status of animal research and place a greater emphasis on explaining behavior rather than mind, especially in research on animals (Watson, 1914). Watson’s notion that the goal of psychology was to predict and control behavior incorporated the vision of psychology as a tool for social control and, therefore, its application to education, industry, and other areas of applied psychology (e.g., Buckley, 1982). Titchener accused Watson of turning psychology into a technology rather than a science (Samelson, 1981). But technology or not, Watson’s view of science as requiring reliability of observations,
public and repeatable, vitiated introspection as a scientific method.Watson argued that verbal reports to a stimulus, in a psychophysical experiment, such as “I see red,” were behavioral in the same way that an animal might be trained to discriminate
the color red from other colors (Watson, 1919). J. B. Watson (1916) proposed that the conditioned motor reflex could be applied to animals and humans and thus form the building block of behavior. Like Titchener, Watson believed that science proceeded by analysis, but instead of the elements of mind, Watson sought the elements of behavior. The conditioned reflex was the elemental unit from which Watson proposed to build a science of behavior. The study of reflexes has a long history within physiology (Boakes, 1984; Fearing, 1930). The Bell-Magendie law (Boakes, 1984; Goodwin, 1999) distinguished between the sensory and motor nerves at the level of the spinal cord. This distinction set the stage for an understanding of reflex action and
stimulated research on the nature and speed of conduction of the nerve impulse that led to the studies of reaction time by Johannes Müller and Hermann von Helmholtz. Russian physiologist Ivan Mikhailovich Sechenov (1829–1905) demonstrated that cerebral processes could affect reflexive action by stimulating certain areas of the brain with salt crystals to decrease the intensity of reflexive movement of a frog’s leg (Boakes, 1984; Koshtoyants, 1965). Sechenov (1863–1965) argued that the cause of psychical or psychological events is in the environment; external sensory stimulation produces all acts, conscious and unconscious, through the summation of excitatory
and inhibitory activity in the brain. He suggested that a science of psychology based on introspective reports of humans is too complex and too subject to “the deceptive suggestions of the voice of our consciousness. . . . [O]nly physiology holds the key to the scientific analysis of psychical phenomena” (Sechenov, 1973 cited in Leahey, 2001; see also, Boakes, 1984).
Ivan Petrovich Pavlov (1849–1936) was able to instantiate Sechenov’s theoretical claims (Koshtoyants, 1965). Pavlov’s research on the physiology of digestion that earned him the Nobel Prize in 1904 involved a method of “sham feeding” in which a fistula, or tube, in the esophagus prevented food placed in the mouth of the dog from reaching the stomach. A second tube inserted into the stomach was used to collect gastric juices. In the course of these experiments, Pavlov noted that gastric secretions occurred not only in response to food in the mouth but also merely to the sight of food, or of the assistant who usually fed the animal. He called these “psychic secretions.” By using a fistula that could collect salivary secretions
for the studies on digestion, Pavlov’s student Stefan Vul’fson noted that not only did the salivary glands respond differently to different substances placed in the mouth, for example, sand, wet food, dry food, but, unlike other digestive organs, they showed the identical response when the dog was teased by only the sight of the substance (Boakes, 1984; Todes, 1997). Vul’fson and Pavlov used mentalistic terms in
describing the reaction of the salivary glands to the sight of food: Dogs “judged,” “sorted out,” or “chose” their responses (Todes, 1997). Pavlov later changed “psychic reflex,” to “conditional reflex,” after experiments demonstrated the experimental
regularity of what his co-worker Tolochinov referred to as a “reflex at a distance” (Todes, 1997, p. 951). Drawing on Sechenov’s early experiments with inhibition of spinal reflexes, the work in Pavlov’s laboratory focused on the establishment (conditioning) and removal (extinction) of reflexes to a variety of stimuli and their control by excitatory and inhibitory activity in the brain. Other investigators who
explored questions of adaptation of organisms to environments paid more attention to the acquisition of new behavior than to the removal of established behaviors (Boakes, 1984). J. B. Watson attempted to demonstrate how research on conditioned reflexes could reveal the origins of complex behavior patterns. In his most famous experiment, conducted with graduate student Rosalie Rayner, he conditioned emotional responses in an 11-month-old infant, “Albert B.” By striking a steel bar with a hammer, Watson and Rayner were able to elicit crying in the infant; when they subsequently paired presentation of a white rat, to which Albert had shown no fear, with the striking of the bar, Albert showed fear to the rat. They reported successfully conditioning fear of the rat in Albert, and, further, the fear generalized to a rabbit, a dog, a fur coat, and a Santa Claus mask (J. B. Watson & Rayner, 1920; see Harris, 1979). The study was more a dramatic demonstration than a carefully controlled experiment, but
nevertheless exemplified Watson’s vision for identifying the origins and development of behavior and provided an approach to the study of the growth and development of children (Mateer, 1918).

Gestalt Psychology

response to the introspective analysis of consciousness advocated by Titchener and the behavioral analysis of J. B. Watson came in the form of an approach to psychology that arose in Germany at about the same time that behaviorism had arisen in the United States. The term gestalt, translated as “whole” or “configuration,” referred to an organized entity that was different from the sum of its constituent parts. The
term was initially introduced by Christian von Ehrenfels, who pointed out that a melody played in two different keys is recognized as such even though the notes in each case are different. He suggested that combinations of elements produced a “gestaltqualität,” or whole-quality, that constituted a new element of consciousness. The use of the term by the triumvirate of Max Wertheimer, Kurt Koffka, and Wolfgang
Köhler referred not to a new element but to the organized nature of conscious experience. The gestalt psychologists opposed what they perceived to be artificial attempts to reduce experience or behavior to constituent parts and then to synthesize
them again into organized wholes, and articulated their views in influential books (e.g., Köhler, 1929). Gestalt psychology was initiated by observations on apparent movement (Wertheimer, 1912), in which two lights located at some distance apart give rise to the experience of one light moving from one location to the other when the
lights go on and off in sequence. The phenomena seemed incapable of explanation by introspective identification of sensory elements. The gestaltists proposed that the introspection appropriate to psychology was a description of experience, a naive introspection that described the experience without any attempt to subject it to analysis. Perceptual phenomena and conscious experience were not the only domains
of gestalt theory; Köhler’s research on chimpanzees (Köhler, 1926) suggested that learning occurred not through trial and error but by insight that resulted from a perceptual reorganization that produced a new way of seeing the problem to be solved. Neither Thorndike’s trial-and-error explanations of learning nor behavioral analysis of organized goal-directed behavior seemed adequate to account for the behavior of the chimpanzees.
The disagreement with the structural approach to mind and the behavioral approach to behavior derived from fundamentally different assumptions about the nature of science. Titchener, and Watson as well, assumed that science proceeded by analysis, by breaking down chemical and material objects into the elements of which they are composed. The elemental analysis that Titchener perceived to be the hallmark
of physics was a nineteenth-century model that had given way to analyses in terms of fields in which forces operated to determine organization of particles rather than particles or elements giving rise to organization (e.g., introducing a magnetic force placed among a random pattern of iron filings organizes the filings in terms of the directions of force). Field theory and the laws of organization were proposed to
account for many phenomena (e.g., Ellis, 1950), not only of perception and problem solving and learning, but of, for example, social behavior (Asch, 1955), child development (Koffka, 1927), and thinking (Wertheimer, 1959), and served to prompt research designed to test theories in these areas.