Generalization of excitation and inhibition after different amounts of training of an avoidance baseline.
After acquisition of a treadle-pressing response maintained by an avoidance contingency, four groups of pigeons received interdimensional discrimination training. For two groups, the positive stimulus was a 1000-Hertz tone correlated with the avoidance schedule and the negative stimulus was noise correlated with extinction. The discriminative stimuli were reversed for the other two groups. For two groups, the test stimuli were presented during extinction without any shocks during the test stimuli, for the other two groups, an unavoidable shock was presented during each test stimulus. Generalization was measured daily during discrimination training by randomly substituting each of six test frequencies for the 1000-Hertz tone. When the 1000-Hertz tone was correlated with the avoidance schedule, the number of responses to it increased and the excitatory gradient became steeper as a function of the amount of training. When the 1000-Hertz tone was associated with extinction, the number of responses to it decreased as a function of days of training and the inhibitory gradient became slightly steeper, provided that responding to the test stimulus was elevated by unavoidable shock. The training effects parallel those obtained with positive reinforcement.