Estes, died quietly at the age of 92. His health had declined steadily in the last three months since his wife of almost 70 years, Kay, died in May. Since then he had spoken repeatedly of wanting to join her. As per his wishes, he was cremated and interred with Kay and their son, Greg, in Illinois.
Our friend, mentor, and colleague, BillWilliam K. Estes’ long and productive career encompassed the science of learning and memory from behaviorism to cognitive science, with seminal contributions to both. Estes (born June 17, 1919) began his graduate studies under the tutelage of B. F. Skinner during the early 1940s.
The United States had not yet entered World War II. The Germans were using a new technology — rockets — to bomb England. As Londoners heard the whine of the rocket engines approaching, they stopped whatever they were doing — eating, walking, or talking — and waited for the explosions. After the rockets dropped elsewhere and people realized they were safe, they resumed their daily activities. Intrigued by these stories from London, Estes and Skinner developed a new conditioning paradigm for rats that was similar, in some respects, to what Londoners were experiencing. This paradigm, called conditioned suppression, was a new technique for studying learned fear (Estes & Skinner, 1941). Estes and Skinner placed hungry rats in a cage that delivered food pellets whenever the rats pressed a lever. The cage also had a metal grid floor wired to deliver a mild shock to the rats’ feet. Normally, the hungry rats pressed the lever to obtain food; but if the experimenters trained the rats to learn that a tone predicted an upcoming shock, the rats would freeze when they heard the tone and wait for the shock. Measuring this freezing behavior allowed Estes to quantify trial-by-trial changes in the learned response. Within a few years, this conditioned emotional response paradigm became one of the most widely used techniques for studying animal conditioning, and it is still in use today.
As soon as he completed his PhD, Estes was called into military service. He was stationed in the Philippines as the commandant of a prisoner-of-war camp, a not-very-demanding job that gave him lots of free time to read the mathematics books sent from home by Kay. When the war ended, Estes returned to the United States and to the study of psychology. Much to Skinner’s dismay, Estes soon began to stray from his mentor’s strict behaviorism. He started to use mathematics to describe mental events that could only be inferred indirectly from behavioral data, an approach quite unacceptable to behaviorists. Years later, in his autobiography, Skinner bemoaned the loss of Estes as a once-promising behaviorist, speculating that Estes’ preoccupation with mathematical models of unobservable mental events was a war-related injury, resulting perhaps from too much time in the hot Pacific sun (Skinner, 1979).
Estes built on Hull’s mathematical modeling approach to develop new methods for interpreting a wide variety of learning behaviors (Estes, 1950). Most learning theorists of that era, including Hull, assumed that learning should be viewed as the development of associations between a stimulus and a response. For example, suppose that a pigeon is trained to peck whenever it sees a yellow light in order to obtain a bit of food. Hull assumed that this training caused the formation of a direct link between the stimulus and the response and that later presentations of the yellow light would evoke the peck-for-food response. Estes, however, suggested that what seemed to be a single stimulus, such as a yellow light, was really a collection of many different possible elements of yellowness and that only a random subset of these elements are noticed (or “sampled,” in Estes’ terminology) in any given training trial. Only the elements sampled on the current trial were associated with the response. On a different trial, a different subset is sampled, and those elements were now associated with the response. Over time, after many random samples, most elements became associated with the correct response. At this point, any presentation of the light activated a random sample of elements, most of which are already linked with the response.
Estes called his idea stimulus sampling theory. A key principle of the theory is that random variation (“sampling”) is essential for learning, just as it is essential for the adaptation of species in Charles Darwin’s theory of evolution through natural selection (Estes, 1950). Estes’ approach gave a much better account than other theories (such as Hull’s) of the randomness seen in both animal and human learning, and his theory helped to explain why even highly trained individuals don’t always make the same response perfectly every time. On any given trial, it’s always possible that (through sheer randomness) a subset of elements will be activated that are not linked to the response. Estes also showed how stimulus sampling theory explains how animals generalize their learning from one stimulus (e.g., a yellow light) to other, physically similar stimuli (e.g., an orange light), as Pavlov had demonstrated in the 1920s.
Estes’ work marked the resurgence of mathematical methods in psychology, reviving the spirit of Hull’s earlier efforts. Estes and his colleagues established a new subdiscipline of psychology called mathematical psychology, which uses mathematical equations to describe the laws of learning and memory. From his early work in animal conditioning, through his founding role in mathematical psychology, to his later contributions to cognitive psychology, W. K. Estes continued to be a vigorous proponent of mathematical models to inform our understanding of learning and memory
W.K. & K.W. Estes Fund
William K. Estes (June 17, 1919 – August 17, 2011) had an enormous influence on psychological science, from his pioneering work in mathematical psychology to his collaborations with colleagues to his mentoring of students, many of whom are now leaders in the fields of learning and memory. He was recognized for his lifetime of contributions with our nation’s highest scientific honor, The National Medal of Science.
Bill also had a special role in APS’s history and success as Founding Editor of our flagship journal Psychological Science. During those years, his wife, Katherine W. (Kay) Estes, served as Founding Managing Editor. Bill and Kay were a team in so many undertakings. The W.K. & K.W. Estes Fund celebrates their contributions to psychological science.
www.psychologicalscience.org/estes-fund
Make a contribution online atA downloadable form is also available on that webpage.
-Mark Gluck,
Rutgers University
Henry L. “Roddy” Roediger, III
Washington University
I came to Purdue University in July 1973 as a brand new assistant professor. A few months before I arrived, Bill Estes had visited. I was sorry to have missed the chance to meet him, but I heard a good story about the visit from several sources.
The Purdue Psychology Department had been seeking a big equipment grant for new computers from NSF. At the time I arrived, there was a hulking machine there called a Linc 8 (it nearly filled a whole room) and two PDP somethings, maybe PDP-8s. They had cords spewing out the back, and if any one was misplaced, the whole system failed. At any rate, Purdue psychologists wanted more computers. Bill had come for a site visit, and he led the visiting team. I heard all this second hand, since I was not there to witness the event itself.
The faculty figured they needed to show off the computers doing something, so they hooked them up to slide projectors. What Bill and the site visit team saw were these massive computers making slide projectors advance at the rate of one slide every two seconds, something a work-study student could have accomplished with no trouble.
At the final meeting, after making an impassioned plea for why the Purdue Department needed three more computers, the Purdue faculty finished speaking. It was Bill’s turn to talk. A long, incredible, silence ensued as people waited for some kind of response from the leader of the site visit team. Finally, Bill said “Does that mean you would need three more slide projectors, too?”
NSF did not give Purdue the grant. This story about Estes was told and retold for a while in the Department. I might have heard an embellished version, but probably not. I got to know Bill a little bit years later, but never worked up the courage to ask about the Purdue site visit.
R. Duncan Luce
University of California, Irvine
Bill and I were among the creators of mathematical psychology during the 1950s. One major accomplishment was the creation of the Mathematical Social Science Board (Robert R. Bush, Clyde H. Coombs, Estes, R. Duncan Luce, and Patrick C. Suppes) that raised NSF funding to run modeling workshops at Stanford University during the summer months in the 1950s and 1960s. A second was the founding in 1964 of theJournal of Mathematical Psychology, which was soon followed by the founding of the Society for Mathematical Psychology. Although our careers frequently overlapped, we never wrote a joint paper. My wife and I often saw Bill and Kay socially when we were both in Cambridge, and we have many warm memories of dinners and concert evenings together as well as the Estes’ annual Holiday Open House. I join others in mourning the loss of a giant in the field.
Rutgers University
The year I entered the University of Minnesota as a freshman, 1939, was a frenetic year of uncertainties and excitement. I was a putative physics major but never became part of that group. Rather, I hung out with friends from high school — Bill Estes, Paul Meehl, and Norm Guttman — in the psychology department, where the “action” and excitement were. It was a time of politics and revolution, Roosevelt, Hitler, Stalin, Franco, Skinner, Hathaway, and Feigl; it was talk, talk, talk and opinion, opinion, opinion. Kay Walker and Keller Breland, who shared graduate student offices on the third ring of the atrium in the psychology building, held forth loudly and obscenely about the virtues of operant psychology while smoking twisted Cajun cigars that Keller had brought from southern Louisiana. (Kay was shedding her “proper lady” upbringing.) Some students were touting Starke Hathaway’s experimental approach to building a personality assessment (the MMPI), others were arguing the merits of various political outlooks, and so on. There were many very bright grad and undergrad students in that group who went on to become famous. Elliott, the psychology chairman and a very proper Harvardian who had hired Skinner at Boring’s suggestion, must have wondered how he got into such a hornet’s nest. As far as I remember, Bill never participated in the violent discussions, but on our walks about campus, it was clear that he had listened.
(Click image to view larger timeline)
Bill was fiercely, but discretely, competitive. I am sure he greatly enjoyed the single B that Paul Meehl got, but we will never know. Bill was comfortable with his talent and accomplishments and tolerant of others.
Meeting Bill on campus was an experience. We’d often cross paths, traveling in opposite directions. I’d greet him, “Hi Bill,” and after walking on for 20 ft. or more, I’d hear, “Hi George.”