Colour versus quantity as cues in reverse-reward-competent squirrel monkeys ( Saimiri sciureus )

Abstract

To assess the relative salience of colour and quantity cues, squirrel monkeys previously trained to reach for the smaller of two quantities of food in a reverse-reward contingency task received colour discrimination training. After initial failure to discriminate between two colours of dots under a differential reinforcement regime, they learned the task when the S− colour was associated with zero reward. The monkeys then showed good retention on the original reverse-reward task of 1 versus 4 with pairs of dots presented in S+ or S− colours. However, on “mismatch” trials of 1S− versus 4S+, only 2 of 4 monkeys tested showed a preference—1 monkey chose based on quantity, the other based on colour. Individual differences and the possible roles of overshadowing and blocking are discussed.