The Perceptual Worlds of Dolphins
Harry J. Jerison University of California, Los Angeles
I have accepted the assignment to speculate about the way dolphins perceive the external world. The issue is the kind raised by Immanuel Kant in his "Critique of Pure Reason" ( Kant, 1787/ 1934), parts of which can be read as an essay on the human perceptual world. In addition to his metaphysics, which need not concern us, Kant presented a useful psychological theory of the structure of the experience of reality, which he described as a priori knowledge. The data for the theory happened to be his personal experience, but it may be possible to suggest something comparable about the dolphin's world.
There are different constraints on theorizing that is to be based on behavioral rather than on experiential data, and there is only behavioral evidence for speculations ("theories") about the mind of the dolphin. One tactic is to imagine an animal's experiences, as suggested by its behavior and by the anatomy and physiology of its sensory and motor systems. The accepted ( Lloyd Morgan's) canon for reconstructing an animal's perceptual world is to identify it with the simplest picture that is consistent with the data. A few unusual features of the world of the dolphin are made evident this way, but the result may be less satisfactory for dolphins than for members of most other species with which this strategy has been followed. Different experiences can be consistent with the same behaviors, and the simplest possible world may not be the world built by the dolphin's brain.
A true picture of the dolphin's perceptual world can be developed only if we accept an additional constraint. A "most parsimonious" explanation for a given behavior must account for the energetic investment of the organism in the neural control of the behavior, as well as for the behavior itself. We must keep in mind that the world of the dolphin is constructed by one of the largest information