Factors influencing the acquisition of tactual random figure discriminations by rhesus monkeys

Rhesus monkeys learned to perform two-object random figure discrimination problems by touch. This performance was compared to the visual acquisition of the same problems (reported earlier). In both modalities, choice latencies were shorter to the correct than to the incorrect figure. As compared to visual, however, tactual learning required significantly more trials to criterion, was independent of stimulus figure complexity, and was characterized by significantly shorter choice latencies. Rotation of the figures 180 deg after criterion performance was achieved, yielded partial recognition of the figures visually, but no recognition tactually. These results are explained by different observational or cue-utilization strategies. The majority of the figure is inspected visually, but only the same small section of the perimeter is used tactually. Thus, restricted use of the available cues characterizes tactual performance and is responsible for generating differences in various measures of learning between vision and touch in the monkey.