In Algona, IA, in 1957, children were funneled into two categories depending on whether they sang in the choir. “The kids that sang tended to be brighter, more middle-class,” Medin says. “Students who did not sing tended to come from the wrong side of the tracks.” He was lumped with the non-singers.
However, despite their poor grades, Medin found his rough friends intelligent and interesting. “There were a lot of things they were very curious about,” says Medin, who is now professor of psychology at Northwestern University (Evanston, IL). “And I just became intrigued by why these kids that seemed so motivated outside of school were failing in school.”
His interest in how individual differences affect learning styles led him to study psychology in college, and, later, to explore the interface between psychology and anthropology. In his career, he has striven to move beyond simplistic laboratory models of how the mind operates and to understand how our expertise and cultural background influence our mental picture of the world. His unique approach led the National Academy of Sciences (NAS) to induct him into its ranks in 2005. His Inaugural Article appeared in the August 28, 2007, issue of PNAS (1).
Space Monkeys
When Medin was a teenager, his family moved to Minnesota, where he attended Minnesota State University in Moorhead (then Moorhead State College). He began as a dual major in psychology and mathematics, but found the psychology teachers more interesting. He would later regret not having pursued more mathematics, but a brush with psychology research as part of a National Science Foundation summer research fellowship spent at the University of South Dakota (Vermillion, SD) got him hooked on studying animal behavior.
In fact, it intrigued him enough that, upon graduating from Moorhead, he committed to the Ph.D. program in psychology at the University of South Dakota. It was 1965, and NASA was racing the Soviets to the moon. Medin won a NASA fellowship in psychology to study the behavior of rhesus monkeys. In terms of sending humans into space, “there was the question of what we knew about perception, learning, memory in monkeys that might be relevant,” he says. “I was probably among the last of the NASA fellowships because they phased them out.”
Medin (Right) and his cousin share an early fascination with science.
Medin wrote his dissertation on how rhesus monkeys perceive shapes. In particular, he investigated whether “information theory” could predict which shapes monkeys could remember. According to information theory, symmetrical figures should require less effort to remember. In fact, some shape features did affect monkey memory, “but symmetry wasn't one of them,” Medin says. While carrying out these experiments, he had the idea that humans' language use might underlie major differences between the way monkey and human brains function. This thought—an interspecies version of the “Whorfian hypothesis” (i.e., that language influences thought)—spawned his interest in comparative psychology.
After completing his dissertation, Medin considered applying for a faculty position. His advisor, Roger Davis, had misgivings. “He told me, ‘Look, you're not going to get a good job from an unprestigious school like South Dakota; you really should do a post-doc,”’ Medin says. “What he didn't tell me is, you're unlikely to get a really good post-doc if you're not from a prestigious school.” But Davis had connections. He had studied under William Estes at Stanford University (Stanford, CA) and had subsequently sent him a star pupil, David Rumelhart, who was inducted into the NAS in 1991. “I think [Davis] wrote Estes and said, ‘I sent you Dave Rumelhart, do me a favor, I've got this green kid. Teach him some stuff,”’ says Medin.
Should Have Learned More Math
It turned out that, green as Medin was, he and Estes were a good match. In fact, Medin had done one of the experiments Estes had proposed in a grant application he had just submitted to the National Institutes of Health. “There were some coincidences,” Medin says. “I think that's what led him to take a chance on me.” At the time, Estes was just moving from Stanford to Rockefeller University (New York, NY), where Medin joined his group in 1968. Within a year, Estes had arranged a position for him as an assistant professor in large part “because my draft board didn't know what a post-doc was,” Medin says.
Estes was one of the founders of mathematical psychology, and around this time, Medin began to wish that he had completed that major in mathematics. “If I could have turned the clock back,” he says, “I would have ignored the yellowed cards that the calculus teacher was using from her notes that were 30 years old, and worked a little harder.”
His work—with monkeys and, for the first time, humans—hinged on constructing mathematical models to describe how animals and children discriminate or categorize. In a typical study, for example, researchers might examine how monkeys or children learn to categorize triangles. To do that, they might reward study participants each time they chose a triangle from a group of shapes. The dominant model at the time assumed that participants would compare new objects to an abstract, average idea of a triangle that they had developed.