A method for examining short-term retention of haptic cues in monkeys

Tasks used to examine short-term memory (STM) in animals have almost exclusively required retention of visual cues. To determine if haptic information can be retained, three rhesus monkeys were trained to perform, using only haptic cues, a simultaneous (SMS) and a delayed matching-to-sample (DMS) task. On each trial, the monkeys felt and responded to a sample stimulus on a centrally located manipulandum. They were then presented two comparison stimuli located on both sides of the central manipulandum. A response matching the comparison stimulus with the sample stimulus was reinforced. In SMS a mean of 2,725 trials was required to reach a criterion of 90% correct. As in DMS performance for visual cues, in haptic DMS the monkeys were capable of above-chance responding at retention intervals of greater than 1 min. This haptic DMS task should be useful for testing STM models, for examining the physiological basis of STM, and for examining drug effects.