THE EFFECT OF HUNGER ON THE LEARNING OF NEW FOOD PREFERENCES IN THE MONGOLIAN GERBIL

A new and more profitable Food type was introduced to three groups of Mongolian gerbils (Meriones unguiculatus). When first presented with t he new food one group was sated, another was hungry and the third grou p was hungry and expected a food shortage. In addition to the new food all groups had access to familiar food during the experimental sessio ns. The group that expected a food shortage had a lower intake of new food than either of the other groups, both in absolute and relative nu mbers. Both the sated and the hungry group ate the same absolute amoun t of new food during the first presentation, but since the sated anima ls had a lower total intake, the new food represented a higher proport ion of the intake for these animals. The animals were then tested duri ng the subsequent days (all groups now hungry). The up that had been s ated showed a stronger preference for the new and profitable food than the hungry group, which in turn showed a stronger preference than the expected food shortage group. This means that in a semi-natural situa tion a strong need may actually decrease the rare of learning. The res ults can be explained iii terms of risk prone/risk aversive behaviour along the lines of previous studies of risk sensitivity in optimal for aging. In an additional experiment it was shown that sated individuals will decrease their total intake of food when presented with both new and familiar food, in comparison with when only familiar food is pres ent. This may have the effect of enhancing learning about the new food .