Formation of Extinction Sets in Monkeys.
ARMY MEDICAL RESEARCH LAB FORT KNOX KY
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Discrimination sophisticated, Old World monkeys received 108 two-choice problems each containing four to eight discrimination trials followed by four extinction trials for four animals and by ten extinction trials for four animals. Following this, they received 108 additional problems with extinction trial length reversed. With ten extinction trials per problem, an orderly increased in the efficiency of extinction occurred, with one-trial extinction occurring in a large proportion of problems. Virtually no tendency to extinguish occurred with four extinction trials per problem. There was a marked increase in responses to the formerly negative stimulus on the second extinction trials. Author