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Sixteen classroom observational studies were conducted to determine natural rates of teacher verbal approval and disapproval in the classroom. Rates of teacher verbal approval and disapproval were measured by the Teacher Approval and Disapproval Observation Record (TAD) over Grades 1 through 12. Teacher verbal approval rates dropped over grade, with a marked drop after second grade. In every grade after second, the rate of teacher verbal disapproval exceeded the rate of teacher verbal approval. These rates are interpreted in terms of reinforcement theory.

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Failures to obtain a peak‐shift and inhibitory stimulus control following massed extinction in the presence of intra‐ and interdimensional stimuli confirm earlier results reported by Honig, Thomas, and Guttman (1959) and by Weisman and Palmer (1969). Peak‐shifts and inhibitory stimulus control were observed when any of the following procedures intervened for 3 min between massed extinction and generalization testing: (1) S+ presented, responding reinforced; (2) S+ presented, responding not reinforced; or, (3) noncontingent food presented in the presence of a dark key. Behavioral contrast was shown not to be a necessary antecedent for the occurrence of peak‐shift or inhibitory stimulus control.

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Rats were trained in a discrete‐trial paradigm with no intertrial interval. The first response changed an auditory stimulus for the remainder of the trial. Shocks were delivered only at the end of the trial cycle. Avoidance contingencies were defined by the conditional probability of shock, given no response (P0), and the conditional probability of shock given a response (P1). The maximal avoidance contingency was P0 = 1.0, P1 = 0, and noncontingent conditions were those for which P0 = P1. In Experiment I, after training on the maximal contingency, three groups of subjects experienced either P0 = P1 = 0, P0 = P1 = 0.5, or P0 = P1 = 1.0. Eight of 10 subjects stopped responding under the noncontingent conditions. Experiment II studied partial contingencies by varying P0 and P1. For one group, P0 was reduced holding P1 = 0. Responding decreased to zero as P0 approached zero. A second group was studied under P1 > 0, holding P0 = 1.0. For three of the six rats in this group, responding decreased to zero with increasing P1. The other three maintained responding as P1 was increased up to the noncontingent, P1 = P0 = 1.0 value. The P0 group was also studied with P0 = P1 > 0, and half of these subjects responded. The results demonstrated two modes of response to weakening or eliminating the avoidance contingency. Some subjects were sensitive to contingency only, and insensitive to changes in shock density. Approximately one half of the subjects were sensitive to both contingency and shock density. This shared control was observed only when P1 > 0.

Pigeons were exposed to stimuli presented on two keys. For some birds, the stimuli varied in a dimension of visual flicker‐rate, and for others they varied in visual intensity. During differential training, concurrent schedules operated, with one stimulus correlated with one schedule and another stimulus correlated with a second schedule that arranged a lower, or zero, rate of reinforcement. The stimuli were alternated randomly on the two keys. Generalization tests were given in which the original two, and seven other stimuli lying in the same dimension, were presented in pairs on the two keys in various combinations. In the generalization test given after differential training, each bird showed peak shift. The data did not support explanation for peak shift that gave critical emphasis to whether stimuli were presented simultaneously or successively during differential training.