Three experiments were performed in this work. The purposes of the experimentation here were, first, to examine the possibility of the acquisition of avoidance response in crayfish, and secondly, to examine the structure of avoidance learning by comparing operant and Pavlovian contingencies within the chelipod-extention avoidance-learning paradigm.
In Experiment I, four groups were constituted by factorially combining the opportunity to avoid or not avoid the US and the opportunity to terminate or not terminate the CS. The results of Experiment I showed that avoidance responses were produced in crayfish within both operant and Pavlovian conditioning paradigms.
In Experiment II, subjects were divided into four groups, and each one of them was respectively exposed to the CSs alone, to USs alone, to the CSs and USs presented unpaired, and no stimuli, to examine the possibility of sensitization of response. The results showed that there was no tendency for sensitization of response to the CS to occur as a result of simple exposure to the CS alone, US alone, or CS and US presented separately.
In Experiment III, subjects were divided into four groups. In the first stage of the experiment, subjects were trained under avoidance conditions with or without CS termination by response, and then shifted under Pavlovian contingencies. The results indicated that avoidance performance of crayfish within the chelipod-extention avoidance-learning paradigm was produced by stereotyped defence reactions with apparent modifiability.