Learning in honeybees as a function of amount and frequency of reward

In the series of four experiments with free-flying honeybees, individual foragers were trained with targets of two different colors that contained 5 or 20 microliters of 50% sucrose solution. The two targets were singly presented in quasi-random sequences on each visit, with the amount of reward to be found on each target perfectly predictable from its color. The number of training visits (4-32) was varied both within and between experiments, and so also was the relative frequency of trials with the 5- and 20-microliter targets (1:1, 2:1, 3:1, and 9:1). At the conclusion of training under each condition, unrewarded responses to the targets were measured in a 10-min extinction test, with the targets presented either separately to two different groups of animals (Experiment 1) or as a pair (Experiments 2-4). When the number of training trials with each target was the same (Experiments 1 and 2), the animals responded more in extinction to the 20-microliter target than to the 5-microliter target, although there was a decline in the overall level of responding to both targets (an overlearning-extinction effect) as the number of training trials increased. After nine times as many, or only three times as many, training trials with the 5-microliter target as with the 20-microliter target, the animals responded more in extinction to the 5-microliter target (Experiment 3); after twice as many training trials with the 5-microliter target as with the 20-microliter target, there was equal responding to both (Experiment 4). The preferences shown in the choice tests of Experiments 2-4 could be simulated rather accurately on the assumptions of a model previously developed to deal with the discrete-trials choice behavior of honeybees and the further assumption that associative strength grows at a rate increasing with amount of reward to a asymptote independent of amount of reward.