A re-examination of animal tropisms

The goldfish, Carassius auratus, was subjected to direct current stimulation in a long, narrow test-tank in an attempt to define and isolate the existence of galvanotropisms in vertebrates (forced, stimulus-bound uniform movements toward the cathode) as a behaviour distinct and separate from taxic (highly variable ‘escape’ or adaptive) movements. Contrary to previous research, subjects spent significantly more time in the cathode half of the tank than in the anode half. Both the velocity and behavioural characteristics of the movements toward the cathode drastically differed from the movements away from the cathode. Stimulus onset and offset responses were noted. The tropistic behaviour patterns evidenced in this research, as distinct from taxes, do not follow traditional conceptions of S-R relationships.