- Thomas R Zentall: Department of Psychology, University of Kentucky, Lexington, KY, United States.
The hypothesis proposed by Macphail (1987) is that differences in intelligent behavior thought to distinguish different species were likely attributed to differences in the of the tasks being used. Once one corrects for differences in sensory input, motor output, and incentive, it is likely that all vertebrate animals have comparable intellectual abilities. In the present article I suggest a number of tests of this hypothesis with pigeons. In each case, the evidence suggests that either there is evidence for the cognitive behavior, or the pigeons suffer from biases similar to those of humans. Thus, Macphail's hypothesis offers a challenge to researchers to find the appropriate conditions to bring out in the animal the cognitive ability being tested.