The pretreatment weighting technique

A common procedure that is frequently used in perceptual studies interested in group differences (e.g., young vs. aged) involves initially equating all subjects in a pretreatment condition by differentially weighting the subjects on a particular stimulus dimension. The experimental treatment of interest is then introduced to these equal-baseline groups. The present article questions the general validity of this procedure by focusing on the critical assumption that the pretreatment weighting and the experimental treatment are independent. A research example is included demonstrating that differentially weighting individuals in order to produce equal-baseline performance may, in fact, provide the basis for later performance differences under the experimental treatment.     

Some temporal factors in the successive comparison of auditory amplitudes.

Under certain conditions the discrimination of successively presented auditory amplitudes appears to be primarily a function of the time intervals between stimulus onsets rather than of either the duration of the stimulus or the silent interval between the tones (interstimulus interval). The results of this study are interpreted in terms of a model containing an acquisition process which continues for a set interval (about 600 msec) subsequent to the onset of the stimulus, even if stimulus offset occurs prior to this time. The onset of another stimulus during this period terminates acquisition. The model also includes a memory process which does not start until acquisition is complete.     

The role of the standard in an auditory amplitude discrimination experiment

The role of the standard in a fixed-standard experiment of auditory amplitude discrimination was examined by varying the proportion of trials on which it was presented. The results suggest that the Os may use different perceptual strategies, depending on the availability of the standard. While they did better on trials containing a standard regardless of the proportion of such trials, their accuracy on both “standard-present” and “standard-absent” trials was positively related to the probability of the particular type of trial. These results conflict with the claim of advocates of the roving-standard paradigm that the O in the fixed-standard experiment does not use the standard but, rather, compares the variable with a long-term referent built up over many trials. The introduction of a second pair of tones, making it a random-standard experiment,, produced considerable response bias tied to the stimulus level and to an overall deterioration in performance.     

Absence of binocular interaction between spatial and color attributes of visual stimuli

The hypothesis that induction of the McCollough effect (spatially selective color aftereffects) entails adaptation of monocularly driven detectors tuned to both spatial and color attributes of the visual stimulus was examined in four experiments. The McCollough effect could not be generated by displaying contour information to one eye and color information to the other eye during inspection, even in the absence of binocular rivalry. Nor was it possible to induce depth-specific color aftereffects following an inspection period during which random-dot stereograms were viewed, with crossed and uncrossed disparity seen in different colored light. Masking and aftereffect in the perception of stereoscopic depth were also nonselective to color; in both cases, perceptual distortion was controlled by stereospatial variables but not by the color relationship between the inspection and test stimuli. The results suggest that binocularly driven spatial detectors in human vision are insensitive to wavelength.     

Teaching gender-related material: The effect of group sex composition on perceptions of a female instructor

This study investigated how group sex composition affects female and male students' perceptions of female instructors who teach in the area of counseling women. Three components of person perception were assessed: cognitive, affective, and behavioral. The cognitive domain included evaluations of the instructor and the subject matter presented; the affective domain included emotional responses to the instructor and the subject matter; and the behavioral domain included actions in response to the instructor, operationalized as the number of questions asked by students. Students with some interest in a career in the helping professions viewed one of two videotapes either with a group of same-sex peers or in a group in which they were the only male or female. One tape described a gender-neutral topic (psychology and the law) and the other described a female gender-related topic (sex bias in counseling women). The same female instructor made both presentations. Students then completed the measures. As predicted, the sex composition of the student group affected person perception, especially in the affective and behavior domains. Recommendations are made for future research.This study was supported by a small grant from the University Research Institute, University of Texas at Austin. Appreciation is expressed to Sherry Fowler, Bob Haverstick, and Kathy Thomas for help with data collection and to Carolyn Bates and Ken Wilgus for coding the open-ended responses. A paper based on this research was presented at the meetings of the American Psychological Association, August 1987.     

Selective adaptation with reversible figures: Don’t change that channel

An adaptation-test paradigm was used in two experiments examining processes underlying the perceived reversals of a rotating Necker cube. Adaptation and test cubes were either the same or different with respect to their visual fields of presentation (Experiment 1) or their sizes (Experiment 2). Results of both experiments indicated that, following subjects’ adaptation to a different cube, reversal rate of the test cube did not differ from that obtained without prior adaptation experience. In contrast, reversal rate of the test cube was elevated following adaptation to the same cube. Additional findings of Experiment 1 were that a test cube presented to the same visual field as the adaptation cube yielded a higher reversal rate than did a simultaneously presented cube in the opposite visual field. Also, the reversal rate of one cube was not influenced by the simultaneous presentation of a second cube. Results of both experiments were interpreted in terms of the fatigue and recovery of multiple, largely independent, localized neural channels. Thus, the results tie reversible-figure illusions to other visual phenomena thought to involve similar fatigue processes within localized visual channels (e.g., tilt, motion, and size aftereffects).     

Spatial disinhibition of orientation analyzers

Following the successive presentation of two masking gratings (M1 and M2), subjects were required to detect the presence or absence of a single vertical line (TS). When the orientations of the two masks were optimal, M1 was able to reduce the masking effect of M2 on the TS. For a vertical TS, disinhibition was maximal when the orientations of M1 and M2 were similar and was minimal when the orientational difference was greater than 15 deg. It is suggested that the spatial selectivity of the disinhibition function reflects the activity of neurons tuned to orientation, and that the disinhibition masking paradigm may be a useful psychophysical technique to measure tuning functions of other feature detectors.     

"I DON'T KNOW WHO TO BLAME": HIV-POSITIVE SOUTH AFRICAN WOMEN NAVIGATING HETEROSEXUAL INFECTION

Women who become HIV infected through heterosexual transmission are faced with the task of making sense of how they became infected. This paper presents a qualitative analysis based on interviews with 35 HIV-positive South African Black women. A specific theme, that blame of a male partner was avoided or disavowed in interviews, is explored in relation to broader contexts concerning gender and HIV. It is suggested that the repeated phrase "I don't know who to blame" expresses gender-differentiated speaking rights. It also protects women from voicing their own anger, guilt and internalization of badness as a result of an HIV-positive diagnosis. Further, it protects women from exposure to male destructiveness and from confronting the possibility that they themselves are implicated in the infection of others. Analysis offers opportunities for exploring how women both resist and repeat dominant discourses and dominant fears related to HIV-infected womanhood.