Marine Mammal Cognition
Dolphin & Numerosity
Home
Experiments
Bibliography
Forum
Contact us
Links
Search
|
A bottlenose dolphin (Tursiops truncatus) discriminates visual stimuli differing in numerosity
Introduction
Numerical competences have been investigated to a quite large extend for many mammal species, and birds. It seems very clear that no animal can “count” as humans do, because real counting is an elaborate ability which is commonly accepted to be based on 5 principles (see definition of counting of Gelman and Gallistel, 1978). But basic numerical competences have been found for quite a number of animal species, and dolphins are not expected to be an exception. In the only study on numerosity carried out with Bottlenose Dolphins, Mitchell et al. (1985) used representatives for definite numbers; and they demonstrated that dolphins were able to discriminate and order amounts.
The present study uses a different paradigm, where the dolphin is asked to discriminate simultaneously presented numbers of visual stimuli. First, we tested for the capability to discriminate stimuli on the basis of their numerosity by systematically controlling for confounding stimulus parameters. Second, we investigated the dolphin’s performance in transfer to novel numerosities.
Subject
The study is carried out with an experimentally naïve male bottlenose dolphin, “Noah”, born and housed at the Dolphinarium of the Zoo Nuremberg, Germany.
Procedure
A) Discrimination training of the numerosities 2 vs. 5
During the first phase, only the numerosities 2 vs. 5 were presented. With the first stimuli used, a number of parameters, such as type, size, and configuration of stimulus elements, covaried with the number feature. In a series of transfer tests, we investigated the influence of these confounding stimulus parameters on the dolphin’s performance.
B) Transfer to novel numerosities
After all confounding stimulus paramters were under control, we tested for transfer to novel numerosities. New number pairings were presented in catch trials (non-reinforced trials) only. We introduced intervening numerosities as well as numerosities outside the former number range. A successful transfer to these new number pairings would suggest a representation of ordinal relations among numerosities in the bottlenose dolphin.
NOTE
The experimental part of this study was completed recently. We will soon present a full report of the results!
Some references
Alsop, B., Honig, W.K. (1991). Sequential stimuli and relative numerosity discriminations in pigeons. J Exp Psych: Animal Behav Proc 17: 386-395
Boysen, S.T., Berntson G.G. (1995). Responses to quantity: Perceptual versus cognitive mechanisms in chimpanzees (Pan troglodytes). J Comp Psych: Animal Behav Proc 21: 82-86
Brannon, E.M., Terrace, H.S. (1998). Ordering of the numerosities 1 to 9 by monkeys. Science 282: 746-749
Clearfield, M.W., Mix, K.S. (2001). Amount versus number: Infants’ use of area and contour length to discriminate small sets. Journal of Cognition and Development 2 (3): 243-260
Davis, H. MacKenzie, K.A., Morrison, S. (1989). Numerical discrimination by rats (Rattus norvegicus) using body and vibrissal touch. J Comp Psych 103: 45-53
Davis, H., Perusse, R. (1988). Numerical competence in animals : Definitional issues, current evidence, and a new research agenda. Behavioral and Brain Sciences, 11: 561-615
Emmerton, J., Lohmann, A., Niemann, J. (1997). Pigeons’ serial ordering of numerosity with visual arrays. Animal Learning & Behavior 25: 234-244
Gallistel, C.R., Gelman, R. (1992). Preverbal counting and computation. Cognition, 44: 43-74
Gelman, R., Gallistel, C.R. (1978). The child’s understanding of number. Cambridge, MA: Harvard University Press.
Meck, W.H., Church, R.M. (1983). A mode control model of counting and timing processes. J Exp Psych: Animal Behav Proc 9: 320-334
Mitchell, R.W., Yao, P., Sherman, P.T., O’Regan (1985). Discriminative responding of a dolphin (Tursiops truncatus) to differentially rewarded stimuli. J Comp Psych 99: 218-225
Pepperberg, I.M. (1994). Numerical competence in an African gray parrot (Psittacus erithacus). J Comp Psych 108: 36-44
Rilling, M. (1993). Invisible counting animals : A history of contributionsfrom comparative Psychology, ethology, and learning. In S.T. Boysen, E.J. Capaldi (Eds.), The development of numerical competence: Animal and human models (pp. 3-37). Hillsdale, NJ: Erlbaum
Rumbaugh, D.M., Savage-Rumbaugh, S., Hegel, M.T. (1987). Summation in the chimpanzee (Pan troglodytes). J Exp Psych: Animal Behav Proc 13: 107-115
Some links
