The visual perception of rigid motion from constant flow fields

Four experiments investigated observers’ judgments of rigidity for different types of optical motion. The depicted structural deformations were of two types: (1) those with nonparallel image trajectories that are detectable from the first-order spatiotemporal relations between pairs of views; and (2) those with parallel image trajectories that can only be detected from higher order relations among three or more views. Patterns were composed of smooth flow fields in Experiments 1 and 3, and of wire frame figures in Experiments 2 and 4. For both types of display, the nonrigidity detectable from the first-order spatiotemporal structure of the motion sequence was much more salient than the deformation detectable only from the higher order spatiotemporal structure. These results indicate that observers’ judgments of rigidity are based primarily on a two-view analysis, but that some useful information can be obtained under appropriate circumstances from higher order spatiotemporal relations among three or more views.     

A twin study of specific behavioral problems of socialization as viewed by parents

Our study focused on the etiology of specific behavioral problems rather than on a global syndrome such as hyperactivity. As a first step in studying specific behavioral problems, we revised the Conners (1970) Parent Symptom Rating questionnaire to improve its factor structure. Our revised instrument and the testretest reliabilities of its 12 scales are described. A classical twin analysis comparing intraclass correlations for 54 pairs of identical twins and 33 pairs of same-sex fraternal twins indicated substantial genetic influence on behavioral problems in schoolaged children. We wish to express our gratitude for the Spencer Foundation's support of this research.     

Engaging “Resistant” Families in Treatment

Many families, when presented with the option of family therapy, are less than eager to participate. This paper comprises the second and third parts of a series on engaging “resistant” families. ¹ 1 The first paper in this series, authored by J. M. Van Deusen, M. D. Stanton, S. M. Scott, and T. C. Todd, is entitled “Engaging “Resistant” Families in Treatment: I. Getting the Drug Addict to Recruit His Family Members” and appeared in the International Journal of the Addictions 15 (7): 1069–1089, 1980. A revised and expanded version of Part II is presented in M.D. Stanton, T. C. Todd, and Associates, The Family Therapy of Drug Abuse and Addictions New York, Guilford, in press.
Part II presents 21 principles and a number of techniques and strategies that have been developed for successfuly recruiting such families. These techniques should be applicable for engaging resistant families with all types of presenting problems. Part III provides an analysis of the important variables involved, along with data on cost efficiency and administrative costs. It was found that when therapists had administrative control of their cases, serving in dual roles as both therapists and drug counselors, the recruitment effort was (a) more effective (i.e., complete families, including both parents or parent surrogates, were recruited in 77 per cent of the cases), and (b) twice as cost efficient. Two-thirds of the non-engaged families were not recruited because the index patient would not allow family members to be contacted. Black families were more difficult to recruit than whites. Data on cost efficiency and on the actual administrative costs of recruiting families are also provided. We conclude that the engagement process requires a revision in therapeutic philosophy, since such families are often desperately in need of help but are unavailable unless therapists make a special effort to reach them.     

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.     

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.