Food avoidance learning in squirrel monkeys and common marmosets

Using a conditioned food avoidance learning paradigm, six squirrel monkeys (Saimiri sciureus) and, six common marmosets (Callithrix jacchus) were test ed for their ability to (1) reliably form associations between visual or ol factory cues of a potential food and its palatability and (2) remember such associations over prolonged periods of time. We found (1) that at the grou p level both species showed one-trial learning with the visual cues color a nd shape, whereas only the marmosets were able to do so with the olfactory cue, (2) that all individuals from both species learned to reliably avoid t he unpalatable food items within 10 trials, (3) a tendency in both species for quicker acquisition of the association with the visual cues compared wi th the olfactory cue, (4) a tendency for quicker acquisition and higher rel iability of the aversion by the marmosets compared with the squirrel monkey s, and (5) that all individuals from both species were able to reliably rem ember the significance of the visual cues, color and shape, even after 4 mo nths, whereas only the marmosets showed retention of the significance of th e olfactory cues for up to 4 weeks. Furthermore, the results suggest that i n both species tested, illness is not a necessary prerequisite for food avo idance learning but that the presumably innate rejection responses toward h ighly concentrated but nontoxic bitter and sour tastants are sufficient to induce robust learning and retention.