Matching-to-sample and oddity-from-sample in goldfish.

Acquisition of three-alternative simultaneous matching-to-sample and oddity-from-sample was investigated. Five goldfish were trained on matching and five on oddity for a minimum of 70 days. Subsequently, six of the fish were trained for 70 days on the other task. Acquisition was similar for oddity and matching. Correct responding started at about chance level and slowly increased to about 75%, with some animals performing at levels of over 85%. Acquisition of oddity following matching and matching following oddity began below chance. Maximal level of performance on second-task oddity was comparable to that on first-task matching. By contrast, the maximal levels of performance when matching was the second task were not as high as that of the same subjects at the end of first-task oddity. All fish exhibited strong color preferences during matching acquisition but not during oddity acquisition. The data demonstrated that goldfish can acquire a discrimination in which the stimulus associated with reinforcement depends on the identity of a second stimulus.