Prolonged visual memory in macaques and man

If a different pair of images is used for each trial, pigtailed macaques can make reliable matches 24–96 h after presentation of the ‘sample’; longer intervals have not been tested.

Abstract

In 'delayed matching to sample' an object or image (the 'sample') is presented, removed, and after a certain delay is presented again together with a second object. The task is to identify ('match') the object previously seen. When the same pair of objects is used repeatedly, one or the other serving as 'sample', monkeys have difficulty making the match after a few seconds. The task has thus been used as a test of 'short-term memory'. The present experiments show, however, that if a different pair of images is used for each trial, pigtailed macaques can make reliable matches 24–96 h after presentation of the 'sample'; longer intervals have not been tested. While the macaques were not as proficient as man in this regard, this may well be a matter of technique in asking them the question. In any event they possess a visual system capable of prolonged retention of detail without benefit of linguistic support or rehearsal.