The appearance of surfaces specified by motion parallax and binocular disparity

The experiments reported in this paper were designed to investigate how depth information from binocular disparity and motion parallax cues is integrated in the human visual system. Observers viewed simulated 3-D corrugated surfaces that translated to and fro across their line of sight. The depth of the corrugations was specified by either motion parallax, or binocular disparities, or some combination of the two. The amount of perceived depth in the corrugations was measured using a matching technique.

A monocularly viewed surface specified by parallax alone was seen as a rigid, corrugated surface translating along a fronto-parallel path. The perceived depth of the corrugations increased monotonically with the amount of parallax motion, just as if observers were viewing an equivalent real surface that produced the same parallax transformation. With binocular viewing and zero disparities between the images seen by the two eyes, the perceived depth was only about half of that predicted by the monocular cue. In addition, this binocularly viewed surface appeared to rotate about a vertical axis as it translated to and fro. With other combinations of motion parallax and binocular disparity, parallax only affected the perceived depth when the disparity gradients of the corrugations were shallow. The discrepancy between the parallax and disparity signals was typically resolved by an apparent rotation of the surface as it translated to and fro. The results are consistent with the idea that the visual system attempts to minimize the discrepancies between (1) the depth signalled by disparity and that required by a particular interpretation of the parallax transformation and (2) the amount of rotation required by that interpretation and the amount of rotation signalled by other cues in the display.     

The Ouchi illusion: An anomaly in the perception of rigid motion for limited spatial frequencies and angles

The spatial parameters underlying a novel illusion of relative motion are characterized. A simple stimulus composed of two sine-wave gratings was sufficient to generate the illusion. We measured the response of subjects to rapid, small-amplitude oscillations of this stimulus behind a fixation point. The effect was clearly strongest for acute angles between the gratings, but only when spatial frequency was between 6 and 11 cpd. We surmise that activity in the grating cells of the primate visual cortex (von der Heydt, Peterhans, & Dursteler, 1992) might be the cause of the illusion. The illusion is potentially an important tool in understanding how higher cortical areas combine disparate motion signals.     

Change in affective state assessed by impaired color-naming of threat-related words

This study investigated the effects of mood induction on Stroop color-naming times for threat-related words. The subjects’ task was to color-name sets of threat-related words and affectively neutral matched control words both before and after mood-induction. Subjects were shown a short film about the medical effects of nuclear war (negative affect manipulation), a humorous cartoon, or no film. A significant and highly reliable color-naming decrement of the threat-related words was observed only after the negative affect manipulation. This indicates that the attentional bias towards the processing of threat-related material observed in clinically anxious or high Trait-Anxious subjects can be induced in initially nonanxious subjects. An incidental recall task included in the procedure provided no evidence of mood state dependent recall.     

Counsellor and client perceptions of the effectiveness of time-limited counselling in an occupational counselling scheme

Counsellors providing brief counselling (6 sessions) in a British Social Services Department completed post intervention questionnaires for 429 clients. These provided information on several measures about the degree to which they felt that their clients had benefitted from the counselling, how far they felt that the number of sessions was adequate, and the nature of the clients' problems. Two hundred and twenty-three of the clients also completed post-intervention questionnaires indicating their degree of satisfaction on a number of measures. There was fair agreement between counsellors and clients that outcomes were satisfactory, and that the number of sessions was adequate, although clients were more satisfied than counsellors. Counsellors identified a range of personal and occupational presenting problems, and around two thirds of problems belonged in the personal domain. Long-tern personal problems received lower satisfaction ratings and were more frequently referred on to other agencies.     

Towards an empirical model of malingering and deception

Two models for the detection of dissimulation in mentally disordered individuals are presented. The first is a heuristic model summarizing useful indicators employed by practicing clinicians. The second and more extensive model integrates research findings from social-psychological and clinical studies towards identifying empirically-tested indicators of malingering and other forms of psychological deception.     

Protection motivation and self-efficacy: A revised theory of fear appeals and attitude change

The effects of fear appeals on persuasion were investigated in a factorial experiment that was designed to test a combined model of protection motivation theory and self-efficacy theory. As predicted, the probability of a threat's occurrence and the effectiveness of a coping response both had positive main effects on intentions to adopt a recommended preventive health behavior. More importantly, the findings provided support for self-efficacy expectancy as a fourth component of protection motivation theory: Self-efficacy had a direct influence on intentions and interacted with two other variables of protection motivation theory. The interaction effect was interpreted in terms of two new decision-making strategies that people use when confronted with a fear appeal: a precaution strategy and a hyperdefensiveness strategy. In addition, the results replicated previous findings on the relationship between self-efficacy expectancy and outcome expectancy. A model incorporating protection motivation theory and self-efficacy theory is presented as a possible general model of attitude change.