Kapp, Frysinger, Gallagher, and Hazelton (1979) have demonstrated that lesions in the amygdala can reduce certain responses commonly associated with fear (e.g., decreases in heart rate). If fear is really reduced, then it should be more difficult to train an avoidance response in lesioned animals because the aversiveness of the stimulus will be reduced.

Assume two groups of rabbits: One group has lesions in the amygdala, and the other is an untreated control group. The following data represent the number of trials to learn an avoidance response for each animal:

Group with Lesions: 15 14 15 8 7 22 36 19 14 18 17 Control Group: 9 4 9 10 6 6 4 5 9

a. Analyze the data using the Wilcoxon rank-sum test (two-tailed).

b. What can you conclude?