Abstract
20 larval leopard frogs (Rana pipiens) were given 40 trials per day for 5 consecutive days in a discriminated-avoidance situation. Light was used as the conditional stimulus (CS), and the unconditional stimulus (US) consisted of scrambled electric current. Ss were matched for size and assigned to 4 cells of a 2 by 2 factorial design. The factors were US intensity (0.4 ma vs 0.8 ma) and type of US (discontinuous vs continuous). Over sessions there was an increase in the number of avoidance responses (p < .005) and a corresponding decrease in the number of no-response trials (p < .05). Discontinuous shock, which facilitates discriminated-avoidance learning in tats, did not affect the level of avoidance responding in tadpoles but did significantly reduce the number of no-response trials (p < .01). This finding suggested that the role of the discontinuous shock in discriminated-avoidance learning may be adventitiously to eliminate responses (e.g., freezing) which are incompatible with the avoidance response.