Leon Kamin

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Leon J. Kamin (born December 29, 1927) is an American psychologist known for his contributions to learning theory and his critique of estimates of the heritability of IQ. He studied under Richard Solomon at Harvard and discovered several important facts about conditioning, including the "Kamin Effect" and the "blocking effect".

Early life and education

Born in Taunton, Massachusetts, Kamin was blacklisted during the McCarthy era[1] and had to find employment in Canada, where he chaired the Psychology Department at McMaster University in Ontario, Canada (1957–68). When he was removed from the blacklist in 1968, he returned to the U.S. and chaired Princeton University's Department of Psychology and later the Psychology Department at Northeastern University in Boston, Massachusetts.


Kamin's most well-known contribution to learning theory was his discovery and analysis of the "blocking effect" (1969). He showed that conditioning an animal to associate a salient conditioned stimulus (CSb), such as a bright light, with a salient unconditioned stimulus (US), like a shock, is "blocked" when CSb is presented simultaneously with another conditioned stimulus (CSa) that was already conditioned to the US. (Kamin used rats in most of his research, but the effect has been found in many animals). The blocking effect is one of the hallmark effects in the study of associative learning in animals, including humans.

Kamin has long opposed the idea that significant personal traits are largely heritable. He became skeptical of the claims of Cyril Burt regarding the heritability of IQ, and published his opinions in a 1974 book The Science and Politics of IQ. He co-authored the controversial book Not in Our Genes (1984) with geneticist Richard Lewontin and neurobiologist Steven Rose. This book, championing the "radical science movement", criticized sociobiology and evolutionary psychology. Kamin is known in some circles for his speculation that the heritability of IQ could be "zero" (Mackintosh, 1998)

He is honorary professor of psychology at the University of Cape Town in South Africa.


In Race Differences in Intelligence (1974), Loehlin, Lindzey & Spuhler wrote (p. 85):

Kamin's more radical assertion of zero heritability, if substantiated, might not render the present book entirely meaningless, but it would certainly require a considerable revision of its language and point of view. In Appendix H we have taken a second look in the light of Kamin's critique at some of the data that provide the main focus for his misgivings, namely the studies of adoptive families and separated identical twins. We do not find these data to be quite as fragile as does Kamin, and we find Kamin's analysis to suffer from a number of statistical and logical problems.

and also (p. 299):

On the whole, then, although Kamin's critique emphasizes some methodological points worthy of attention in conducting and evaluating studies in this area, it does not, in our view, constitute an unbiased survey of the data, and it suffers from enough logical and statistical difficulties that Kamin's "reasonably prudent man" will want to think twice before accepting his conclusions.


  • The Science and Politics of IQ (1974)
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  1. (Kamin, 2005)


  • Kamin, L. J. (1969). Predictability, surprise, attention, and conditioning. In B. A. Campbell & R. M . Church (Eds.), Punishment and aversive behavior (pp. 279–296). New York: Appleton-Century-Crofts.
  • Kamin, L.J. (2005). Letter to the Editor, New York Review of Books, May 26.
  • Mackintosh, N. (1998). IQ and Human Intelligence. Oxford: University Press. pp. 78–79.
  • Loehlin, Lindzey & Spuhler (Freeman, 1975). Race Differences in Intelligence (ISBN 0-7167-0754-3)

External links