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This experiment investigated the tendency to escape from a situation requiring effortful responding. Five human subjects responded in a situation where the response mechanism required 20‐lb force to operate; responses were reinforced according to a variable‐interval schedule. A subject escaped from this situation by emitting a vocal response which produced a 60‐sec “easy period”. During the easy period the reinforcement contingency was switched to a response mechanism requiring 1 lb to operate. It was found that: (1) Escape responding could be conditioned and maintained by producing the easy period; the easy period did not maintain escape responding when the force requirement in the normal situation was equated with it. (2) The rate of escape responding was a function of the magnitude of the force normally required. (3) When easy periods were scheduled after fixed ratios, pausing from the end of the previous easy period to the first escape response was noted. It was concluded that a situation requiring high‐force responding is a negative reinforcer. The pattern of fixed‐ratio responding suggests that this reinforcer produces typical schedule control in human subjects.

From observer records, a count was made for each child, in a group of disadvantaged children in an experimental preschool, of usage and acquisition of descriptive adjectives, with and without noun referents. Procedures were sought which would effectively modify the low rates of adjective‐noun combinations in the everyday language of all the children. Time in school, intermittent teacher praise, and social and intellectual stimulation were not effective in changing the low rates of using adjectives of size and shape. Group teaching effectively increased rates of using color‐ and number‐noun combinations in the group‐teaching situation, but was ineffective in changing rates of usage in the children's “spontaneous” vocabularies. By operating directly on the children's language in the free‐play situation, making access to preschool materials contingent upon use of a color‐noun combination, significant increases in such usage were effected in the spontaneous vocabularies of all the children. Preschool materials apparently functioned as powerful reinforcers. Though traditional teaching procedures were effective in generating adjective‐noun combinations in that restricted situation, it was only through application of environmental contingencies that color names as descriptive adjectives were effectively and durably established in all the children's spontaneous vocabularies.

Extinction of Sidman avoidance behavior by eliminating the noxious stimulus was studied in Sprague‐Dawley rats with bar‐pressing as the response. Each of three subjects was trained and extinguished on each of the following schedules in a different order: nondiscriminated, response‐shock interval = 20 sec, shock‐shock interval = 5 sec; nondiscriminated, response‐shock interval = 40 sec, shock‐shock interval = 5 sec; discriminated, response‐white noise interval = 15 sec, noise‐shock interval = 5 sec, shock‐shock interval = 5 sec. Less than one 4‐hr session was required for extinction for all procedures. When a warning stimulus was present, resistance to extinction increased. Subjects did not, however, respond to avoid the signal. Only small differences in extinction were found after training on different schedules with no warning signal.

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