An evaluation of the associative strength of a partially reinforced serial CS

Three experiments examined the factors that are responsible for producing a high rate of autoshaped keypecking in pigeons when the conditioned stimulus is followed by varying consequences. In the first experiment, a single group received three serial conditioning schedules presented on different keys. The AB⁺ schedule consisted of trials in which A was followed by B, which, in turn, was followed by food. The CD⁺C° schedule consisted of reinforced CD pairings plus presentations of C alone. The EF^+/0 schedule consisted of a mixture of reinforced and nonreinforced EF pairings. It was found that responding was most rapid during C, slowest during E, and at an intermediate rate during A. In spite of this ordering A was chosen in preference to C, when these stimuli were presented simultaneously. In Experiments 2 and 3 the schedules AB⁺A° and AB^+/0 were presented to separate groups. The rate of responding during A was substantially greater in the former schedule, yet it was found that this stimulus was equally ineffective as a conditioned reinforcer in both groups. We propose that autoshaped keypecking is composed of two types of response, a conditioned response and an orienting response, which are governed by different processes.     

Nonresident Suicides in England: A National Study

Little is known about the numbers and characteristics of people who travel away from home before dying by suicide. Therefore, this studied attempts to identify the sociodemographic characteristics, location, and method of suicide in people who died distant from home, in a national sample. Data were collected on all English suicides and a patient population; nonresident suicides resided in one Health Authority but died in a different one. Twelve percent of suicides were nonresident and features of these included: young age, social adversity, and severe mental illness. In conclusion, both individual‐ and area‐based factors are likely to contribute to suicide away from home.     

Contribution of somesthetic information to the perception of body orientation in the pitch dimension

This study investigated the contribution of otolithic and somesthetic inputs in the perception of body orientation when pitching at very slow velocities. In Experiment 1, the subjects' task was to indicate their subjective postural vertical, in two different conditions of body restriction, starting from different angles of body tilt. In the "strapped" condition, subjects were attached onto a platform by means of large straps. In the "body cast" condition, subjects were completely immobilized in a depressurized system, which attenuates gravity-based somesthetic cues. Results showed that the condition of body restriction and the initial tilt largely influenced the subjective postural vertical. In Experiment 2, subjects were displaced from a vertical position and had to detect the direction of body tilts. Results showed that the threshold for the perception of body tilt was higher when subjects were immobilized in the body cast and when they were tilted backward. Experiment 3 replicated the same protocol from a supine starting position. Compared to results of Experiment 2, the threshold for the perception of body tilt decreased significantly. Overall, these data suggested that gravity-based somesthetic cues are more informative than otolithic cues for the perception of a quasi-static body orientation.