Truly Random Control Group in Pavlovian Conditioning of Planaria (Dugesia Dorotocephala)

Abstract

Both Jensen (1965) and Dyal (1973) have called for the introduction of the truly random control group in studies of planaria to provide an appropriate baseline against which to evaluate the associative effects of CS-US pairings. Accordingly, an experiment was performed comparing a Pavlovian excitatory conditioning group both with the traditional unpaired control group and a Rescorla truly random group. Three conditions were compared (six planaria in each) using a trace conditioning procedure (3-sec. light CS followed by a 1-sec. shock US). The major results of the experiment were that (a) the Pavlovian excitatory group showed an increase in performance only for the contraction CR measure, (b) head turns and combined CR measures showed only decreases or no changes in performance in any of the groups; (c) the performance of the truly random control group was between the Pavlovian excitatory and unpaired control groups, providing support for the notion that the latter is not truly a control condition but an inhibitory one.