Factors influencing perceived angular velocity

The assumption that humans are able to perceive and process-angular kinematics is critical to many structure-from-motion and optical flow models. The current studies investigate this sensitivity, and examine several factors likely to influence angular velocity perception. In particular, three factors are considered: (1) the extent to which perceived angular velocity is determined by edge transitions of surface elements, (2) the extent to which angular velocity estimates are influenced by instantaneous linear velocities of surface elements, and (3) whether element-velocity effects are related to three-dimensional (3-D) tangential velocities or to two-dimensional (2-D) image velocities. Edge-transition rate biased angular velocity estimates only when edges were highly salient. Element velocities influenced perceived angular velocity; this bias was related to 2-D image velocity rather than 3-D tangential velocity. Despite these biases, however, judgments were most strongly determined by the true angular velocity. Sensitivity to this higher order motion parameter was surprisingly good, for rotations both in depth (y-axis) and parallel to the line of sight (z-axis).     

Perceptual learning in pigeons: Decreased ability to Discriminate samples mapped onto the same comparison in many-to-one matching

Humans often treat two stimuli that are associated with a common response as similar in other contexts. They do so presumably because those stimuli become conceptually or perceptually more similar to each other (perceptual learning). An analogous phenomenon may occur in pigeons when they are trained with a matching-to-sample procedure in which more than one sample is mapped onto the same comparison. In the present research, pigeons were trained to select one comparison following either of two samples (S₁ or S₂) and to select the other comparison following either of two different samples (S₃ or S₄). When the samples were then presented as positive and negative stimuli in a simple successive discrimination, samples that had been associated with the same comparison during original training (e.g., S₁ vs. S₂) were more difficult to discriminate than were samples that had been associated with different comparisons (e.g., S₁ vs. S₃). Thus, it appears that perceptual learning occurs in pigeons as well.     

Formulas for component scores

General formulas for obtaining scores for individuals on components (factors derived from correlation matrices with unit communality estimates) are given. They are specialized to give Hotelling's formula for principal component scores. Formulas for scores on components rotated from principal components are developed.The final version of this paper was prepared while the author was a U. S. Public Health Service Fellow at the Center for Advanced Study in the Behavioral Sciences.     

Scaling a simplex

A least-squares solution for scaling the variables of a Guttman simplex is developed. The procedure yields a ratio scale, two varieties of interval scale, and orders the variables. A measure of the goodness of fit of the scale to the data is suggested. An example of the application of the method is given. The problem of non-positive correlations is discussed.I am indebted to Professor Lloyd Humphreys for suggesting this problem. Mr. Joseph Levin independently has arrived at the results of the first section of the paper. The final version of this paper was prepared while the author was a U. S. Public Health Service Fellow at the Center for Advanced Study in the Behavioral Sciences.     

Varimax solution for primary mental abilities

The varimax solution for Thurstone's classic Primary Mental Abilities study is presented. Comparisons between the factors of Thurstone's original subjectively rotated factor pattern, Zimmerman's subjectively revised solution, Wrigley, Saunders, and Neuhaus' quartimax results, and the present varimax factor matrix are made by finding correlations between factors defined by these four solutions. It is pointed out that any possible ultimate merit of the varimax solution should be based on its psychological meaningfulness and on the rationale of the varimax criterion—not on its relationship to the other studies.The computations for this paper were done on Illiac, an electronic computer of the Digital Computer Laboratory of the University of Illinois. Mr. S. M. Hunka assisted in these computations.     

Book reviews

Sans résumé

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Book reviews

     

Fixing Identity by Denying Uniqueness: An Analysis of Professional Identity in Medicine

Cultural forces such as film create and reinforce rigidly-defined images of a doctor's identity for both the public and for medical students. The authoritarian and hierarchical institution of medical school also encourages students to adopt rigidly-defined professional identities. This restrictive identity helps to perpetuate the power of the patriarchy, limits uniqueness, squelches inquisitiveness, and damages one's self-confidence. This paper explores the construction of a physician's identity using cultural theorists' psychoanalytic analyses of gender and race as a framework of analysis. Cultural theorists' politically-motivated work provides an excellent point of departure for destabilizing parts of the authoritarian medical hierarchy that can damage a student's professional development. Drawing on such discourse, this paper examines the processes by which a doctor's identity becomes rigidly defined and fixed by daily training. It finally proposes a way for a medical student to extrapolate himself from the current definitions of this identity and create a broader, more malleable concept of professional identity by defining himself from outside of, rather than through, difference.     

The Motivational and Instantaneous Behavior Effects of Contexts: Steps Toward a Theory of Goal‐Directed Behavior1

Contextual conditions affect behavior in 2 ways: (a) They confront people with opportunities and obstacles that affect their motivation to take action; or (b) they instantaneously shape performance, regardless of a person's motivation and even without subjective acknowledgment of the conditions. Traditionally in psychology, the immediate behavioral consequences of a context are disregarded. Based on our theory of goal‐directed behavior, we are able to disentangle the instant and the motivational behavioral consequences of contexts. In an example study, 40% of the variation in performance among 660 Swiss and Spanish pupils was explained by motivational differences. Instantaneous constraints and facilitations imposed on people's acts, in turn, revealed a set of Switzerland‐ and Spain‐specific limitations and affordances (hit rate = 97.5%).     

Effects of Prenatal Social Stress on Offspring Development: Pathology or Adaptation?

ABSTRACT— In nonhuman mammals, the social environment in which pregnant females live is critical for their offsprings' brain development, endocrine state, and social and sexual behavior later in life. Social instability during pregnancy generally brings about a behavioral and neuroendocrine masculinization in daughters and a less pronounced expression of male-typical traits in sons. We favor the hypothesis that such behavioral effects of prenatal social stress are not necessarily "pathological" (nonadaptive) consequences of adverse social conditions. Rather, pregnant mothers could be adjusting their offspring to their environment in an adaptive way.