SERIAL-LEARNING WITH A WILD CARD BY PIGEONS (COLUMBA-LIVIA) - EFFECT OF LIST LENGTH

Pigeons (Columba livia) learned 3-, 4- or 5-item lists prior to subset and wild card tests. On the latter, a novel item replaced I of the li st items. Pigeons who learned 5-item lists responded accurately on all subset pairs (AB, BC, and AC) and on all types of 3-item wild card tr ials (WBC, AWC, and ABW). Pigeons who learned 4- and 5-item lists resp onded at chance levels of accuracy on all subsets that did not contain a start or an end item (BC, BD, and CD, respectively, on 4- and 5-ite m subset tests). On wild card trials, they exceeded chance levels of p erformance only when the wild card replaced the last item (ABCW and AB CDW trials). Monkeys (Cebus apella) trained to produce a 5-item list p erform accurately on all subsets and wild cards. (M. R. D'Amato and M. Colombo, 1988, 1989). These differences provide strong evidence that pigeons and monkeys form qualitatively different representations of li sts containing four or more items.