International Journal of Comparative Psychology

The common marmoset is a nonhuman primate with a body size similar to an adult rat (approximately 250 – 450 g). This study examined the use of marmosets for behavior research on learning, focusing on the behavioral consequences of audiovisual stimuli (neither food nor liquid used as a reinforcer). A tablet (iPad®) was placed in each marmoset’s individual living cage during the experiment. On the tablet screen, nine small soundless videos of different nonhuman primate species were simultaneously presented. If the marmoset touched any of them, the touched video was zoomed-in on the screen; this was accompanied by the sound of primates chattering as the response consequence. After 2 months of repeated training sessions (10 min/day, 2 or 3 days/week), eight of the ten marmosets established the screen-touch behavior. In an extinction test for the response consequence, the screen-touch response to any of nine primate videos was examined after the presentation of a black screen instead of the above consequence. The number of touch responses decreased compared with baseline control values in three marmosets, whereas responses did not decrease in four marmosets. For the latter marmosets, it was considered that the stimulus changes from the videos to the black screen played a possible reinforcer to maintain the behavior in this test. These findings indicate that the screen-touch behavior, a new learned behavior in the nonhuman primate, could be an operant behavior with an audiovisual response consequence.