Effects of manipulating incentive visibility during the baiting phase of delayed-response problems

Abstract

Rhesus monkeys were given 960 delayed response (DR) problems. The incentive was either visible or not visible during the baiting phase of each problem, and a 0-, 5-, 10-, or 20-sec intraproblem delay was imposed. Performance was substantially better when the incentive could be seen during the baiting phase. When the incentive was visible during baiting, at all stages of training performance decreased as a function of increased chance levels after short delays, and the rate of improvement with training was comparable after each of the four intraproblem delays. When the incentive was not visible during the baiting phase, an inverse relationship between performance and delay duration became evident only during the later stages of training. On the initial problems performance was at chance levels, and although improvement with training was evident, the rate of this improvement was inversely related to delay duration. The findings were interpreted in terms of Fletcher's orienting response analysis of DR performance.