Frontal granular cortex in the monkey has been shown to possess a functional specificity rivaled only by sensory and motor cortex. The delayed response, interpreted by Jacobsen as a test of immediate memory, is a reliable indicator of bilateral frontal-lobe damage in infrahuman primates.1,9,19Lesions in other parts of the cerebrum affect performance on the delayed response only minimally and inconsistently.4,12,18 Following the original observations by Jacobsen, it was shown that minor variations in the test procedure, variations which seem to leave the desideratum of the test intact, affect the sensitivity of the test. One of these demonstrations was that monkeys with bilateral frontal-lobe resections can be made to respond effectively on the delayed response when retained in darkness during the delay period.14Another showed the effectiveness of a predelay reward in improving postoperative delayed-response performance.6Since the delay qua delay remains unaffected by the