The Story of Psychology (47 page)

How could it enlighten human beings about their own minds to harness a dog in a box, start a metronome ticking for fifteen seconds, then drop some meat powder in a bowl inside the box, and repeat this process until at the sound of the metronome saliva would drip from the dog’s mouth even though the meat powder had not yet been delivered? Many psychologists, when they first heard about this experiment, said that it represented a type of association that accounted for only simple forms of behavior in animals; the researcher, however, believed that the principle he had discovered would explain even the most advanced and complex forms of behavior in human beings.
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These experiments and many like them were part of a bold attempt, beginning at the end of the nineteenth century, to answer—actually, to eliminate from discussion—the most perplexing and intractable problems of psychology: those having to do with the nature of mind. Among them:

These were but a few of the questions about the nature of mind, mental states, and the processes of thinking that philosophers, theologians,
and protopsychologists had long sought to answer, though their efforts created more puzzles than they solved.

There was, however, another and totally different answer to such questions, though it was abhorrent to most philosophers and psychologists. Mind is an illusion; there is no incorporeal self within us; our mental experiences, including consciousness, awareness of self, and thinking, are only physiological events taking place in the nervous system in response to stimuli.

Over the centuries a few materialist philosophers suggested this alternative in vague and unconvincing terms, but as the physical and physiological sciences developed, the hypothesis became increasingly specific and plausible. By the latter half of the nineteenth century, Helmholtz and a number of other physiologists were linking simple sensations to electrochemical events in the sensory nerves, and followers of Wundt were beginning their effort to construct a whole psychology out of the elemental components of sensation and perception.

Toward the end of the century the rejection of “mentalism” (the belief in mind as a separate essence) gained support from a quite different quarter—animal psychology, a field in which interest had been sparked by Darwin’s demonstration of the link between humankind and the other species. At first some biologists and psychologists had assumed that animals possess thought processes similar to, though simpler than, our own; in the 1880s, George Romanes, an English biologist, explored animal psychology through “introspection by analogy”; he asked himself what he would do were he the animal in any given situation. But in 1894 the zoologist C. Lloyd Morgan—the researcher who offered two kinds of caterpillars to chicks and two colors of corn kernels to chickens—sliced this approach to the bone with a version of Ockham’s Razor:
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Even the intricate tricks performed by pet dogs, Morgan said, could be explained in terms of reflexes and simple associative learning; there was
no need to assume the existence in the animals of higher mental functions.

Jacques Loeb, a German-born biologist, went even further. During the 1890s, when he was teaching in the United States, he argued on the basis of wide-ranging evidence that a good deal of animal behavior consists of “tropisms,” a term he used for all involuntary responses of worms, insects, and even higher animals to stimuli. In his view, much or most animal behavior consists of such tropisms, the creature being no more than a stimulus-driven automaton.
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The implication of all this seemed clear to a growing number of psychologists: if human beings are related to animals, and if animal behavior can be explained without mentalist concepts, then part of human behavior—perhaps even all of it—can be, too. The answer to the intractable questions about the nature and operations of the mind might be utterly simple: mind does not exist, or if it does, it can be ignored, since it is not only unobservable but unnecessary to the explanation of behavior.

Behavior—
overt, visible, indisputable action
—that
is the real subject of psychology, rather than memory, reasoning, will, and all the other unseen processes imagined by mentalist psychologists. Not conjectures and hypotheses about invisible functions, but
laws
derived from observable phenomena, such as the cat’s learning to escape from the puzzle box, could be the substance of a thoroughly objective and rigorously scientific psychology. Such was the thinking of many psychologists in the 1890s and the early 1900s, long before the word “behaviorism” had been coined or the theory’s tenets set forth.

The animal experiments mentioned above exemplify two different principles of behaviorism: the laws of natural learning (the chickens’ associating a particular color with the reward of the sweet-tasting corn, the cat’s associating a step on the treadle with escape and food), and the laws of conditioning (the dog’s salivating at the sound of the metronome, a stimulus artificially linked to the salivary reflex). These laws were discovered by two men of dissimilar backgrounds, training, and personality, one a brilliant and dedicated psychologist, the other a physiologist who
was scornful of psychology and doubted that it could be regarded as a science.

The first was Edward Lee Thorndike (1874–1947), a psychologist of such catholic and diverse interests that some historians have classified him as a functionalist, others as a behaviorist, and he himself as neither.
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Except for one year, he spent all of his long career in psychology at Teachers College, Columbia University, where he researched and wrote fifty books and 450 articles dealing with educational psychology, learning theory, tests and measurements, industrial psychology, language acquisition, and social psychology. For good measure he produced such unusual items as a teachers’ list of the twenty thousand words students most often encountered in general reading, a rating of American cities according to how desirable they were to live in, and a highly popular dictionary. Our interest in Thorndike, however, is focused on his work as a graduate student, when, notwithstanding his later demurral, he was very much a behaviorist.

Born in Massachusetts, Thorndike, the son of a Methodist minister, was a homely, lonely, and painfully shy child who found satisfaction in his studies. Exceptionally gifted, he ranked first or second in all his high school courses and graduated from Wesleyan University in 1895 with the highest average achieved there in fifty years. He found the basic undergraduate psychology course dull but James’s
Principles of Psychology
entrancing. He went on to Harvard for graduate work, planning to study English, philosophy, and psychology, but after two courses with James he was fully committed to the last of these.

Despite his admiration for James, he chose to do graduate research on a very un-Jamesian topic, “the instinctive and intelligent behavior of chickens.” Later in life he said that his motive had been “chiefly to satisfy requirements for courses and degrees…I certainly had no special interest in animals.”
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Perhaps, but no doubt a shy person (as he still was at the time) would find animals easier to work with than people. James approved the project and Thorndike bought a batch of chicks, which, for lack of laboratory space, he housed in his room until his outraged landlady ordered him to get rid of them. When he told James of his problem, James, going far beyond the bounds of professorial duty, allowed Thorndike to install them in the cellar of his house.

There, using stacked books, Thorndike built a maze with three blind
alleys and a fourth leading to an adjoining enclosure in which were food, water, and other chicks. When he put a chick in the maze, it raced in and out of the blind alleys, peeping loudly, until it blundered to the exit; when he put it back in again and again, it slowly got better at finding its way out. Clearly, there was no intelligence at work but something much simpler. In Thorndike’s words:

Those sentences contained the seed of behaviorist theory.

The following year, after being rejected by a young woman he had proposed to, Thorndike felt it necessary to flee from Cambridge. He transferred to Columbia University to complete work for his Ph.D. under James McKeen Cattell, who was then in the middle of his effort to measure intelligence by anthropometric tests. Though Thorndike too would later do research in mental testing, for his dissertation he continued his animal-learning studies. From fruit and vegetable crates he built fifteen puzzle boxes of various designs, and in the attic of an old university building began studying the ability of cats (plus a few dogs) to learn how to escape.

In some boxes his cats could escape by performing a single action: stepping on a treadle, pushing a button, or pulling on a loop of string. In others, escape required multiple actions such as pulling on the loop and then moving a stick, and in one experiment Thorndike released the door only if the cat licked or scratched itself. Driven by fierce ambition—Thorndike meant to (and did) reach the top of his profession in five years—he worked so hard in the attic with his animals that in less than a year he had arrived at several findings that leaders in the field at once recognized as being of major importance. The New York Academy of Sciences invited him to talk about his results at a meeting in January 1898; in June,
Science
published a paper by him on his work; his thesis appeared as a monograph supplement to
Psychological Review
late in the year; and the American Psychological Association had him make a presentation at its annual meeting in December.

Thorndike’s findings, though simple, had significant implications.
First, the cats had not learned to escape by means of reasoning or insight; rather, by trial and error they slowly eliminated useless movements and made the connection between the appropriate action and the desired goal. They learned nothing from seeing how an experienced cat escaped, or from having Thorndike manipulate their paws to release the door of the box. All the cats learned to escape when only a single response was required, but more than half of them never learned to escape when two responses were required.

From all this, Thorndike formulated a theory of “connectionism,” expressed in two laws of learning.

One he called the Law of Effect. The puzzle box was a stimulus that elicited a number of responses; the effects of most were “annoyers” (failures to escape or to reach the food), but one was a “satisfier,” which yielded both escape and food. Annoyers and satisfiers selectively “stamp in” (or, as Thorndike later said, “reinforce”) certain stimulus-response connections and weaken or eliminate others. The effect of any action thus determines whether it becomes the response to a given stimulus or not.

The second law he called the Law of Exercise. Other things being equal, “a response will be more strongly connected to a stimulus in proportion to the number of times it has been connected with that situation and to the average vigor and duration of the connection.”

Thorndike’s monograph had an immediate effect on psychological thinking. It lent new, research-based meaning to old philosophic notions of associationism; it provided convincing support for C. Lloyd Morgan’s dictum against assuming higher mental functions if lower ones could explain behavior; and it established animal experimentation as the pattern for most learning research for the next half century.

While later researchers (and Thorndike himself) would somewhat modify the Law of Effect and greatly qualify the Law of Exercise, the two laws became the basis of behaviorist psychology, human as well as animal. For although human behavior is vastly more sophisticated than that of cats, behaviorists argued that it is explicable by the same principles; the difference, Thorndike said, is simply that “the number, delicacy, and complexity of cell structures” in the human brain make for a corresponding “number, delicacy, and complexity of associations.”
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He even held that the reason human culture develops so slowly is that it is the result of trial-and-error learning with accidental success, the same method by which animals acquire associations.