Abstract # 146:

Scheduled for Friday, June 22, 2007 05:00 PM-07:00 PM: Session 14 (South Main Hall) Poster Presentation

Transitive Inference in Two Species of Prosimian Primates

E. L. MacLean, D. J. Merritt and E. M. Brannon
Duke University, B203, CCN, LSRC Building, Box 90999, Research Drive, Durham, NC 27708, USA
     Transitive inference has interested comparative psychologists due to its potential to reveal logical thought in animals. Several primate species including chimpanzees, squirrel monkeys, and rhesus macaques have demonstrated impressive abilities to solve problems transitively. Here, we present evidence of transitive inference in prosimians. 3 male ringtailed lemurs (Lemur catta) and 3 male mongoose lemurs (Eulemur mongoz) were trained to choose the higher-ranked stimulus from pairs of adjacently-ranked stimuli in a 7-term series of arbitrary photographs (A+B-, B+C-, C+D-, D+E-, E+F-, F+G-, G+H-). Subjects were subsequently tested on their ability to choose the higher ranked stimulus from previously untrained nonadjacent pairs (e.g, BD). Binomial Sign Tests [a=0.05] showed that lemurs responded above chance expectations on all nonadjacent pairs, demonstrating an ability to make transitive inferences. Further, one-way ANOVAS [a=0.05] revealed increased accuracy and decreased reaction time at greater ordinal distances. Because transitive reasoning may be particularly important for species with linear dominance hierarchies (Bond et al., 2003) we compared the performance of highly-social ringtailed lemurs to that of the less-social mongoose lemurs. Both species learned multiple pairwise associations similarly, but ringtailed lemurs outperformed mongoose lemurs during initial transitive tests [t-test, a=0.05] corroborating the predictions of the social complexity hypothesis. These data indicate that prosimians, like anthropoid primates, show transitive inference and provide further evidence that social complexity may promote the ability to represent ordinal relationships.