Binocular cues in the perception of distance of a point source of light

The ability to make egocentric distance estimates of a single point source of light, seen in darkness and without the cues of changing size and luminance, was investigated in sixteen observers. The attenuation required to maintain constant luminance, when the target was viewed from different distances, was shown to follow the inverse square law providing the angle subtended by the light was less than 20 s arc. Distance changes were also simulated by means of a split mirror which produced vergence cues, or by test lenses to provide accommodation cues. Over the range 0.5 to 9.2 m distance estimates were surprisingly accurate, although there was some overestimation of near and underestimation of far distances. Most observers made good judgements when only convergence cues were varied, whereas no observers made consistently good judgements when only accommodation cues were varied. The difficulties are discussed in terms of the accommodation-convergence link. When distance was simulated by changing convergence and accommodation cues, estimates were not as good as when real distance was changed. Since good estimates were made with brief target exposures, these judgements were not based on subsequent convergence or accommodation changes. It is suggested that the metric or reference against which the apparently absolute judgements were made was the efferent demand signal associated with a 'resting' position of convergence in darkness.     

ILLUSTRATING FEMINIST THEORY

Feminist theory holds that many of the pathological behaviors observed in patients result from their position in the social hierarchy. The goals of the demonstration detailed in this article are to show the impact of current gender roles on the psychological well-being of women and men and to generate understanding and discussion of the problems that relative status can create in the therapeutic relationship. This teaching demonstration draws parallels between the Zimbardo (1971) prison experiment and the impact that assignment to low-and high-power roles can have on the psychological health of women and men. Students are asked to rate men and women on some of the diagnostic criteria that the Diagnostic and Statistical Manual of Mental Disorders (American Psychiatric Association, 1994) associates with Axis I and II diagnoses. The students watch a video of Zimbardo's prison study and then rate the prisoners and guards. This demonstration provides another explanation for gender patterns in psychopathology by demonstrating that psychologically healthy White males will develop different patterns of psychopathology depending on whether they are placed in a dominant or subordinate role. When placed in the subordinate role, they exhibit behaviors typically seen in women clients; when placed in a dominant role they exhibit behaviors commonly associated with male clients. This exercise demonstrates the unhealthy nature of the gender roles for both women and men.     

Book reviews

TOATES, F. Animal Behaviour: A Systems Approach. Chichester: John Wiley and Sons. 1980. Pp. 299. Hardback £17. Paper back £6.40 ISBN 0 471 27724.

DICKINSON, A. Contemporary Animal Learning Theory. Cambridge: University Press. 1980. Pp. 177. Hardback £12.50. Paperback £3.95. ISBN 0 521 23469 7.