Abstract # 2236 Poster # 145:

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

Serial Order Processing in Ring-tailed Lemurs (Lemur catta)

D. J. Merritt, E. L. MacLean, S. Jaffe and E. M. Brannon
Duke University, Center for Cognitive Neuroscience, Durham, NC 27708, USA
     Research over the last 25 years has demonstrated that animals are able to organize and retrieve ordered sequences without language. One method that has proven useful in examining serial processes in animals is the simultaneous chaining paradigm (SCP). In the SCP, arbitrary stimuli are shown on a touchscreen monitor, and the animal is trained to select all items in a predetermined order (e.g. A-B-C-D-E). Tests with two-item subsets drawn from the list (e.g. B-D) have revealed qualitative cognitive differences between pigeons and Old/New world Monkeys. Specifically, monkeys are able to order all subset pairs successfully, whereas pigeons’ cannot order pairs that do not contain an end-item. Further, monkeys show position-dependent reaction-times (RT), whereas pigeons do not. In the present study, we trained two ring-tailed lemurs to learn a series of 3, 4, and 5-item lists to a 50% accuracy criterion. Following training, the lemurs were tested with all possible subset pairs derived from the 5-item list. Binomial Sign Tests [a=0.05] showed performance was above chance on all pairs with the exception of pairs AB and CD. Further, the lemurs showed position-dependent RTs to both the first subset item [r(336)=0.25, p<0.05], and second subset item [r(390)=0.42, p<0.05]. Overall, performance was very similar to that of monkeys, and dissimilar to that of pigeons. This suggests that lemurs and monkeys may share mechanisms for serial organization that date to a common primate ancestor.