Escape conditioning in snakes employing vibratory stimulation

Abstract

Eight rat snakes were given 50 paired presentations of light and vibratory stimulation. Ss were tested in a two com-partment chamber with a 12 hr. interval between each trial. Moving from one compartment to the other terminated and per-mitted escape from the vibratory stimulus. Data from two Ss was discarded because of inadequate responsiveness. Except for the terminal block of trials Ss demonstrated a progressive decline in escape time. Individual Ss, however, were highly variable in their performance. Previous investigations of escape conditioning in snakes have used temperature as the aversive stimulus. Kellogg & Pomeroy (1936) placed water snakes in a water maze containing cold water. A correct response permitted escape into a warm goal compartment. The resultant learning curves showed a high degree of intra-and inter-S variability but did demonstrate a gradual drop in overall response time. Instead of using heat as a reinforcing condition, Wolfle & Brown (1940) attempted to use it as an aversive stimu-lus. Essentially no learning was demonstrated when snakes were run, in a multiple T-maze having a dry surface with a high temperature, to a shaded pan of cool water. Wolfle and Brown also attempted using shock as an aversive stimulus. They found it unsatisfactory in that the snakes either did not respond or else re-sponded so strongly as to make learning impossible. Preliminary attempts from this laboratory using varying current and voltage ratings provided by constant current and constant voltage AC and DC sources confirmed this finding. An alternative possibility for an aversive stim-ulus is vibration. The present report describes an attempt to obtain escape conditioning in snakes using vibration as an aversive stimulus. Method Ss were eight rat snakes, six of which were yellow rat snakes, Elaphe obsoleta quadrivittata, and two were the similar Everglades or "orange" rat snake, Elaphe obsoleta rossalleni. The length of the snakes varied from