PERCEPTION OF PICTORIAL SPACE BY BUSHMEN*

A new test for measuring the ability to perceive pictorial depth was used with children of two remote Bushman populations (!Xu and Kxoe), as well as with a sample of adult Bushmen drawn from these populations and a sample of urban Zulu children. The results show that subjects of apparently little sophistication are capable of perceiving depth when confronted with a ‘geometric’ figure. They also show surprising inter-group differences which cannot be easily explained by differences of environmental experience.     

Autism and Accuracy in Adolescent Perceptions of Friends' Sexual Attitudes and Behavior

This study uses data from adolescents matched with data from their friends to examine whether reference group effects on adolescent sexuality should be thought of as operating through the sharing of norms or the modeling of behavior. We observe that perception of attitudes has such a trivial reality component and such a strong autistic component that it cannot serve as a mechanism of peer influence. Perception of sexual behavior has a reality component which is as large as its autistic component, and large enough to serve as a route of influence. We reach two conclusions: (1) Reference group effects on adolescent sexual behavior probably work through behavior modeling rather than through normative influence. (2) Studies which infer peer influence on sexual behavior using only perception of peers will arrive at erroneous conclusions.     

TESTICULAR SELF-EXAMINATION: VALIDATION OF A TRAINING STRATEGY FOR EARLY CANCER DETECTION

Testicular self-examination (TSE) can lead to early diagnosis and treatment of testicular cancer, the third leading cause of death in young men. We evaluated the effectiveness of a brief and specific checklist for teaching TSE skills. Ten men were videotaped while performing testicular self-examinations before and after training. The TSE training resulted in large and significant increases in the number of TSE steps completed and duration of the TSE. Two urological validation measures supported the improvements observed in the mens' self-examinations. Subjects reported continued performance of TSE during a follow-up telephone interview. This pilot study indicates that a brief and specific checklist is an effective strategy for teaching early cancer detection skills.     

Preferences for Individual Video Games as a Function of Their Emotional Effects on Players

Video games vary in terms of the emotional states they elicit from players. These differences in emotional reactions, in turn, help account for differential preferences of individual games. The three independent dimensions of pleasure-displeasure, arousal-nonarousal, and dominance-submissiveness were used to assess emotional impacts of individual games. In addition, a preference measure was constructed to evaluate attraction toward, versus avoidance of, specific games. In Study One, a group of subjects provided data on emotional responses to 22 common arcade video games and a different group rated their preferences for the same games. The emotional impact of video games was highly unpleasant, moderately arousing, and moderately dominance-inducing; thus, the predominant emotional response to these games was aggression, anger, or hostility. I n Study Two, subjects visiting a video game arcade were recruited and assigned to play two games each and to report their reactions to each game immediately after playing the game. Results showed that greater feelings of pleasure, and separately of arousal, while playing video games resulted in higher preferences for the games and that greater dominance (significant only for males) also led to higher preferences. It may be beneficial, therefore, to experiment with more arousing and more dominance-inducing game designs which are not necessarily unpleasant or which definitely yield high pleasure.     

Superimposition of response-independent reinforcement

Studies that have superimposed response-independent reinforcement (or reinforcers scheduled by contingencies placed on the absence of responding) upon conventional response-dependent schedules are reviewed. In general, providing alternative sources of reinforcement reduced response rates below the levels observed when alternative reinforcement was absent. However, response-rate elevation was sometimes found, particularly when rates of superimposed response-independent reinforcement were low. Superimposition of schedules providing reinforcers contingent on the absence of responding usually produced more severe response-rate decrements than superimposition of response-independent reinforcement. A variant of Herrnstein's equation, which assumes that some of the alternative reinforcers function as if they were delivered by baseline response-dependent source of reinforcement, is in qualitative agreement with the overall body of results obtained, and can predict both increases and decreases in response rate as resulting from superimposed reinforcers.     

Behavioral contrast in fixed-interval components: effects of extinction-component duration.

Seven albino rats were exposed to a multiple schedule of reinforcement in which the two components (fixed interval and extinction) alternated such that a presentation of the extinction component followed each fixed-interval reinforcement. In baseline sessions, the duration of the extinction component was constant and always one-third of the fixed-interval value. Probe sessions contained a probe segment in which the duration of the extinction component was increased; the response rate in fixed-interval components during the probe segment was compared with the response rate in the segments preceding and following the probe. The effect of increasing the duration of the extinction component was studied under three values of fixed interval: 30 s, 120 s, and 18 s, in three successive conditions. Response rate within fixed intervals was a direct function of duration of the extinction component. Pausing at the beginning of the fixed interval decreased as extinction duration increased. These effects were larger and more consistent for the shorter fixed-interval values (18 s and 30 s). These results indicate a functional relation between relative component duration and responding. For the component providing more frequent reinforcement, this could be stated as an inverse relationship between relative component duration and response rate. This relation is similar to findings regarding the ratio of trial and intertrial duration in Pavlovian conditioning procedures, and suggests that behavioral contrast may be related to Pavlovian contingencies underlying the multiple schedule.     

Varying response-reinforcer contiguity in a recycling conjunctive schedule

Three experiments describe the effects of manipulating the frequency of response-reinforcer contiguity in a recycling conjunctive schedule. The schedule arranged that a reinforcer was delivered after 30 s provided at least one response had occurred; otherwise the next cycle started immediately. In Experiment 1, this schedule produced the typical pause–respond–pause pattern, with most responses at mid-interval; and, when a limited number of contiguities between responses and food delivery were added, the pattern became more like the monotonic scallop seen on fixed-interval schedules. In Experiment 2, the schedule was initially presented with an additional contingency that allowed contiguity on every trial. Fixed-interval-like behavior occurred and tended to persist as contiguities were gradually eliminated. In Experiment 3, the recycling conjunctive schedule alternated with a condition in which a large number of contiguities occurred. The pause–respond–pause pattern and fixed-interval-like performance occurred with few or many contiguities, respectively. The results of all three experiments illustrate how contiguity interacts with a small number of other variables to determine performance on interval schedules and illuminate previous findings with fixed-interval and fixed-time schedules.