Parallel discrimination of subjective contours defined by offset gratings

Recent physiological studies (von der Heydt & Peterhans, 1989) suggest that the orientation of subjective contours is encoded very early in the visual system (V2 in monkey). This result is seemingly at odds with existing psychophysical data which suggest that the detection of subjective contours involves selective attention. It is argued that certain subjective contours are registered in a reflexive (bottom-up) manner by the visual system but that selective attention may be needed to gain access to this representation. To assess this suggestion, a visual-search task was used in which subjects were to detect the presence of a horizontal (vertical) subjective contour (defined by offset gratings) in a variable number of vertical (horizontal) subjective contours (also defined by offset gratings). When there were no competing organizations within the display, detection was indeed independent of the number of nontarget distractors, that is, selective attention was unnecessary. In a second experiment, we found that a curved form (a crescent defined by subjective contours) was easier to detect in a background of vertical bars (also defined by subjective contours) than vice versa, namely, a search asymmetry paralleling those found by Treisman and Gormican (1988). A final experiment showed that when the horizontal and vertical bars of the first experiment formed textured regions, they could be discriminated at very brief display durations (30–120 msec), However, when the line terminations aligned along the subjective contour were tapered rather than abrupt, discrimination dropped off with the degree of tapering. The latter result is consistent with the assumption that the registration of subjective contours in V2 involves the integration of responses from aligned, end-stopped cells found in VI (von der Heydt & Peterhans, 1989).     

Whose Gene Is It? A Case Discussion About Familial Conflict over Genetic Testing for Breast Cancer

A multidisciplinary group of genetic and other professionals discuss a complex case of familial conflict over access to genetic information. One twin wishes to know the results of her deceased mother's tests for BRCA1 mutations; a second twin objects to researchers making this information available. As the case discussion unfolds, the apparent facts of this case are called into question and the lines of ethical certainty become less clear.     

Text-contingent color aftereffects: A reexamination

Five experiments reexamined color aftereffects contingent on the semantic properties of text (Allan, Siegel, Collins, & MacQueen, 1989). The influence of different assessment techniques and the effect of eye movements and overlapping contour information on the induction of color aftereffects by word and nonword letter strings were determined. Experiment 1 showed that no aftereffect was found when a traditional method of assessing color aftereffects was used. Experiments 2 and 4 demonstrated color aftereffects forboth words and nonwords, but only when subjects fixated the same locus during induction and testing and only when assessed with the technique described by Allan et al. (1989). If, however, eye movements were made during induction, no color aftereffect was obtained (Experiment 3). Induction to nontext patterns with properties similar to those of text but with fewer overlapping contours resulted in a strong color aftereffect (Experiment 5). These results suggest that the color aftereffect contingent on text is very weak and is not dependent on semantic factors, but that it is a product of induction to local color and orientation information.     

Reverie: between thought and prayer

Abstract:  Taking inspiration from a quotation by Lao Tzu, this paper considers 'reverie' as a dynamic process of containment as well as a state of mind. Reverie as a quality of thought akin to prayer is explored in the relationship between self and other. In infant observation, the paper contemplates the development of a baby's capacity to reach beyond the personal world to an archetypal experience of being held, where the creation of an internal space in mind could indicate the beginnings of spiritual awareness. 'Maternal/analytic reverie' views the passage of unconscious communication between patient and analyst as the result of a 'window' opening in the meniscus of the analyst's self. 'Paternal/supervisory reverie' reflects on the impact on a patient of an extra containing mind of a supervisor. 'Archetypal reverie' considers the transforming impact of numinous dreams on the psyche, and reflects on the power of prayer. Drawing on clinical examples from these four areas, the aim is to demonstrate the usefulness of the 'void within' and the perceptive function of emptiness in the 'doors and windows' of our mind.