The rotating square illusion

Twenty subjects viewed displays of square and trapezoidal luminous dot figures rotating about a vertical axis in both polar and parallel projections. The frequency of reported oscillation of the rotating figures was as high for the squares as for the trapezoids, provided that the squares contained static slant information in the form of internal texture gradients. Previously reported oscillation effects using shapes other than trapezoids have generally been unreliable, with a subject as likely to see rotation as oscillation for a given cycle, and then only in parallel projection. As a consequence, linear perspective information in trapezoidal shape has been taken to be the indispensable element for obtaining a strong oscillation effect. The authors argue that in the construction of the rotating object, a required condition for reliably producing the effect is a violation ofsome optical constraint regarding slant information, not necessarily one involving linear perspective.     

Perception of surface curvature and direction of illumination from patterns of shading

Three experiments examine the perceptual salience of shading information for the visual specification of three-dimensional form. The observers in these experiments were required to estimate the surface curvature and direction of illumination depicted in computer-synthesized images of cylindrical surfaces, both with and without texture. The results indicate that the shininess of a surface enhances the perception of curvature, but has no effect on perceived direction of illumination; and that shading is generally less effective than texture for depicting surfaces in three dimensions. These and other findings are used to evaluate the psychological validity of several mathematical analyses of shading information that have recently been proposed in the literature.     

Conditional reasoning and causation

An experiment was conducted to investigate the relative contributions of syntactic form and content to conditional reasoning. The content domain chosen was that of causation. Conditional statements that described causal relationships (if mean value of cause, then mean value of effect) were embedded in simple arguments whose entailments are governed by the rules of truth-functional logic (i.e., modus ponens, modus tollens, denying the antecedent, and affirming the consequent). The causal statements differed in terms of the number of alternative causes and disabling conditions that characterized the causal relationship. (A disabling condition is an event that prevents an effect from occurring even though a relevant cause is present). Subjects were required to judge whether or not each argument's conclusion could be accepted. Judgements were found to vary systematically with the number of alternative causes and disabling conditions. Conclusions of arguments based on conditionals with few alternative causes or disabling conditions were found to be more acceptable than conclusions based on those with many.     

Assessment of human obesity: The measurement of body composition

The most common methods of assessing degree of obesity in humans are reviewed. These include anthropometry, somatotyping, bodyweight, skinfold calipering, densitometry, and several nondensitometric procedures. The evidence suggests that bodyweight may often be an unreliable and invalid index of obesity. The parameters influencing its inaccuracy are discussed. These include age, height, sex, muscularity, and degree of obesity or amount of recent weight loss. The most reliable and valid measures of human bodyfat are generally the most complicated and impractical. Compromise assessment procedures involving nonintrusive measurement of subcutaneous fat and selected anthropometric dimensions may offer an incomplete but welcome improvement over sole reliance on bodyweight as an index of obesity.     

A different form of agraphia: Syntactic writing errors in patients with motor speech and movement disorders

Three patients are described who displayed syntactic writing errors in combination with a motor speech disturbance and impaired motor limb function. Two of the patients had bulbar amyotrophic lateral sclerosis (ALS). Agraphia appeared when verbal communication was no longer possible. Autopsy in one patient disclosed only lesions consistent with ALS. The third patient had palilalia and chorea and, although not aphasic, his written language showed persistent syntactic errors. We hypothesize that the agraphia in these patients occurred because of the combination of disordered feedback from the motor speech apparatus and limbs.     

Drug use and deviation from self-concept norms

The more the deviation from a sex-and-grade, self-concept score norm (as indexed on a pair-comparisons, adjectival inventory), the greater the incidence of reported drug use. This assertion applies (a) to both sexes (teenagers) for beer and wine, cigarettes, hard liquor, and marijuana, and (b) to males alone for speed and LSD.The first-named author developed the deviancy scale; both authors processed data. In the latter task, they were assisted by Mrs. Edith P. Ferguson, wife of second-named author.     

MODIFICATION OF THE EXCESSIVE INAPPROPRIATE CLASSROOM BEHAVIOR OF TWO ELEMENTARY SCHOOL STUDENTS USING HOME-BASED CONSEQUENCES AND DAILY REPORT-CARD PROCEDURES1

Two experiments investigated home-based reinforcement contingencies to control excessive behavior in normal classrooms. Subjects were, respectively, a 12-yr-old fifth-grade boy and a 9-yr-old fourth-grade boy, each in a separate classroom and with a different teacher. Following baseline observations in which observers recorded several categories of student behavior and teacher-student interaction, separate conferences were held including parents of the two children, the principal, teachers, and experimenters. A daily report-card procedure was agreed on, stipulating a one-day suspension from school following three successive “undesirable” daily report cards as well as the supervision of home-based privileges and other reinforcers usually contingent on satisfactory daily reports. Measurements of daily rates of teacher attention indicated no important change in this variable throughout the various experimental conditions. The daily report procedure significantly reduced disruptive classroom behavior. In a second experiment, a teacher-operated timer cued her own time-sample observations. Reliability measures revealed that the teacher could accurately measure the child's behavior while she was teaching the class. The procedure was ultimately successfully expanded to the teacher's total contact hours each day.