Consummatory contrast: A conserved character?

RINALDI, M. A. & MUZIO, R.N.

Buenos Aires

Congreso; XIVth Biannual Meeting of the International Society for Comparative Psychology.; 2008

International Society for Comparative Psychology (ISCP, USA)

Successive negative contrast effect (SNCE) is shown through a lower response level observed in animals subjected to an unexpected downshift in reinforcement compared to animals with a constant low reward. The SNCE has been found in mammals, both in instrumental and consummatory conditions. Studies performed in the rest of the vertebrates groups yielded no evidence of instrumental contrast, paying little attention to consummatory contrast. The goal of the present work was to study the presence of the consummatory SNCE in the toad Bufo arenarum. A two-compartment apparatus was used; the start compartment was dry and the goal compartment, filled with different NaCl saline solutions as reinforcers. Latency response and weight variation were measured. Three experiments were carried out, where a group of toads was trained with deionized water (pre-shift) and then, suddenly changed to a 200mM, a 225mM or a 250mM NaCl solution (post-shift); control group was always trained with the latter solution. Toad’s performances confirmed previous data showing there is no instrumental contrast in amphibians, but there was a tendency to show a consummatory contrast response. Results are discussed in the framework of the evolution of the frustration behavior, where consummatory contrast could represent an evolutionary conserved behavior.