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Sexual behavior between rabbits was automatically recorded by means of electrodes attached externally to the unrestrained animals. Current flowed only when the animals came into physical contact; the duration and amplitude of the current flow provided a means of automatic differentiation between sexual and other types of physical contact. Various temporal aspects of sexual behavior were revealed: (1) copulation was preceded by a series of thrusts that occurred at a constant frequency of 13 to 14 thrusts per sec; (2) the duration of a copulation was about 1.5 sec and could be as brief as 0.3 sec; (3) copulation was much more likely during the hours between dusk and dawn despite constant illumination; (4) copulations occurred in groups or “runs” characterized by many copulations within a few hours; (5) each run began with a high rate of copulation that often decreased over time; (6) between runs, several hours or days passed with little or no sexual activity; and (7) a run of copulations was noted at the end of every 16‐to 20‐day period (which corresponds to the known period of pseudopregnancy in rabbits) whether or not other runs occurred within this period.

Each of four groups of monkeys were trained on a different simultaneous discrimination procedure involving a vertical line as the correct choice. Each group, after acquiring the discrimination, was tested for generalization along the dimension of line tilt. Monkeys that learned to select the vertical line when the alternative choices were distinguished from the correct choice by two aspects (brightness and absence of line) showed almost complete tilt generalization (flat gradient). Monkeys that learned to select the line when the alternatives were distinguished only by the absence of the line showed poor tilt discrimination (generalization gradient slightly peaked at vertical). Monkeys developed a good tilt discrimination when nonvertical lines were gradually introduced by progressively darkening them on the previously blank alternatives. Monkeys developed a tilt discrimination with the lowest error rate when only horizontal alternatives were gradually introduced and then pairs of alternatives progressively closer to vertical were made available.

This research demonstrated some of the conditions under which retarded children can be taught to imitate the actions of adults. Before the experiment, the subjects were without spontaneous imitative behavior, either vocal or motor. Each subject was taught, with food as reinforcement, a series of responses identical to responses demonstrated by an experimenter; i.e., each response was reinforced only if it was identical to a prior demonstration by an experimenter. Initially, intensive shaping was required to establish matching responses by the subjects. In the course of acquiring a variety of such responses, the subjects' probability of immediate imitation of each new demonstration, before direct training, greatly increased. Later in the study, certain new imitations, even though perfect, were never reinforced; yet as long as some imitative responses were reinforced, all remained at high strength. This imitativeness was then used to establish initial verbal repertoires in two subjects.

Pigeons were trained to respond in a two‐link, concurrent‐chain schedule. Pecks on each key during the concurrent initial links occasionally produced a 5‐min terminal link, during which only that key was operative. Food reinforcement and various intensities of shock were scheduled during the terminal links. When shock was contingent on response, the effect of shock was greater on terminal‐link responding than on initial‐link responding. When shock was independent of response, the effect was reversed, with larger changes in initial‐link responding than terminal‐link responding. In general, shock was found to affect behavior most drastically when behavior could, in turn, affect the rate of shock.

A non‐verbal teaching program, combined with reinforcement and extinction (Program Group), was compared with reinforcement and extinction alone (Test Group) in teaching retarded children to discriminate circles from ellipses. In the Program Group, fading techniques were used to transfer stimulus control from “bright vs. dark” to “form vs. no‐form” and then to “circle vs. ellipse”. The Test Group had the task of learning the circle‐ellipse discrimination with no prior teaching program. With the program, seven of 10 children learned the circle‐ellipse discrimination. Without the program, one of nine learned. The eight Test‐Group children who failed to learn circle vs. ellipse were then given the opportunity to learn the form no‐form discrimination by reinforcement and extinction alone, without fading. Six of the eight learned, but only three of these six then learned circle vs. ellipse on a second test. All seven Program‐Group children who had learned form vs. no‐form also learned the circle‐ellipse discrimination by means of fading; each of the seven made fewer errors than any of the three who succeeded on the second test. Children who failed to learn circle vs. ellipse adopted response patterns incompatible with the development of appropriate stimulus control.