Abstract # 17:

Scheduled for Thursday, June 21, 2012 03:00 PM-03:15 PM: Session 4 (Camellia ) Oral Presentation


A. M. Barnard1, K. D. Hughes1, R. R. Gerhardt1, L. DiVincenti Jr2,3, J. M. Bovee3 and J. F. Cantlon1
1Department of Brain and Cognitive Science, University of Rochester, 430 Elmwood Ave, Rochester, NY 14642, USA, 2School of Medicine and Dentistry, University of Rochester, 3Seneca Park Zoo
     When choosing a food patch or sizing up a neighboring troop, primates benefit from accuracy in assessing quantity, yet, how primates mentally represent number is still undetermined. In humans, there is evidence of two nonverbal numerical systems: an object-file system for quantities less than 4 that can represent objects discretely and an analog system for larger quantities that represents number by their comparative sizes and distances (i.e., their ratio). To understand if these systems are also present in primates, we presented two experiment-naïve olive baboons (Papio anubis) sets of numerical judgements. Initially, both animals were tested only with the number pair 1 vs. 2. Our task assessed ability to discriminate between pairs containing small (1-4), large (5-8), or span (small vs. large) numbers of food items presented simultaneously or sequentially. Baboons successfully discriminated all pair types in both presentation types (binomial tests, p<0.001) except for large pairs presented sequentially (p=0.45). Baboons also successfully discriminated pairs containing quantities above 4 (binomial tests, p<0.01). Performance was modulated by the ratio between the numerical values of the sets on simultaneous trial (r(27)=0.43 and 0.52, p<0.05) and for one baboon on sequential trials (r(27) = 0.67, p<0.05 and 0.31, p>0.05). This ratio effect demonstrates that the animals spontaneously conceive of numerical values in an analog format (rather than as object files) and represent ‘number’ as a single continuum.