Picture perception: An analysis of visual compensation

Although geometric information is altered when a picture’s viewing point is changed, such changes often do not affect perception. Two experiments assessed pictorial perception relative to the distortions introduced by viewing point dislocation. Results provide a psychophysical demonstration of pictorial compensation and suggest that it is based on the discrepancy between the actual and an assumed-correct viewing position. An explanation of pictorial compensation is offered that could be applied to direct picture perception and to picture-in-a-picture perception.     

On the discriminability of stimulus duration.

The performance of pigeons trained to detect differences in the duration of stimuli was analysed using a matching model of signal detection. Two white stimuli, S1 and S2, differing in duration, were arranged with equal probability on the center key of a three-key chamber. S1 was systematically varied from 5 seconds to 25 seconds while S2 remained constant at 30 seconds. On completion of the center-key stimulus, a peck on the center key turned on the two red side keys. A left-key response was "correct" when S1 had been in effect on the center key and a right-key response was "correct" on S2 trials. A correct response produced a 3-second magazine light accompanied intermittently by food. Incorrect responses produced 3-second blackouts. Detection performance was measured under two procedures. In the first, the obtained reinforcement ratio was uncontrolled by allowing the number of food reinforcements obtained for correct left- and right-key responses to vary as the stimuli were changed. In the second procedure, the presentation of food reinforcement was controlled by holding the obtained reinforcement ratio constant. Discriminability changed as a function of stimulus differences under both procedures. No such trend was found in response bias.     

Empirical sleep assessment in the home: A convenient,inexpensive approach

We have previously reported on a sleep assessment device (SAD) that addresses shortcomings inherent in self-report sleep data and polysomnography. The SAD produces a sleep record by tape recording subjects' verbal responses to auditory cues spaced at fixed intervals throughout the night. In prior studies, the SAD proved to be a reliable and valid assessment tool according to electroencephalographic comparisons. Herein, we report on the unassisted home use of the SAD by eight normal volunteers and four bedmates. Subjects and bedmates completed sleep questionnaires for 12 nights and subjects also employed the SAD the last 6 nights. Comparisons of subjects and bedmates self-report sleep data before and during SAD use indicated that the SAD did not disrupt sleep. Subjects were able to self-administer successfully the SAD in their homes. SAD data closely matched subjects' self-report data. The present study found the SAD to be an accurate, unobtrusive, and easily utilized empirical measure of sleep in the natural environment. In so doing, it extends the demonstrated reliability and validity of the SAD from the sleep laboratory to the home with normal sleepers.     

Processing of threat-related information in rape victims

We investigated selective processing of threat information in persons with posttraumatic stress disorder (PTSD) by using a modified Stroop procedure. Subjects were 15 rape victims with PTSD, 13 rape victims without the disorder, and 16 nontraumatized control subjects. They were asked to name the color of four types of words: specific threat (rape-related) words, general threat (related to physical harm and death) words, neutral words, and nonwords. Rape victims with PTSD evidenced a longer response latency for color naming of rape-related words than for other target-word types. Response latencies of non-PTSD victims and nonvictim control subjects did not differ across word types. Possible mechanisms underlying the selective processing of threat material are considered, and clinical implications are discussed.     

Interpersonal Reactions to Depression and Physical Disablllty In Dyadic Interactions1

Examined the interpersonal responses of persons engaged in dyadic interactions with confederates who enacted either depressed or socially appropriate roles and appeared either with or without a physical disability. Subject negative evaluations of confederates were indirectly obtained from a thought-listing measure. The overt behaviors of subjects were surreptitiously recorded on videotape and measures of verbal and nonverbal behavior were acquired. Subjects spoke less to the depressed targets and had significantly higher rates of negative evaluations of these persons. In addition, subjects gazed less at the depressed confederates. These effects were not moderated by target physical appearance. Findings are discussed as they relate to social models of depression and the stigmatizing effects of disability.     

The interaction between stimulus and reinforcer control on remembering.

In a symbolic matching-to-sample task, 6 pigeons obtained food by pecking a red side key when the brighter of two white lights had been presented on the center key and by pecking a green side key when the dimmer of two white lights had been presented on the center key. Across Part 1 and Parts 6 to 10, the delay between sample-stimulus presentation and the availability of the choice keys was varied between 0 s and 25 s. Across Parts 1 to 5, the delay between the emission of a correct choice and the delivery of a reinforcer was varied between 0 s and 30 s. Although increasing both types of delay decreased stimulus discriminability, lengthening the stimulus-choice delay produced a greater decrement in choice accuracy than did lengthening the choice-reinforcer delay. Additionally, the relative reinforcer rate for correct choice was varied across both types of delay. The sensitivity of behavior to the distribution of reinforcers decreased as discriminability decreased under both procedures. These data are consistent with the view, based on the generalized matching law, that sample stimuli and reinforcers interact in their control over remembering.     

Confidence depends on level of aggregation

The credible intervals that people set around their point estimates are typically too narrow (cf. Lichtenstein, Fischhoff, & Phillips, 1982). That is, a set of many such intervals does not contain the actual values of the criterion variables as often as it should given the probability assigned to this event for each estimate. The typical interpretation of such data is that people are overconfident about the accuracy of their judgments. This paper presents data from two studies showing the typical levels of overconfidence for individual estimates of unknown quantities. However, data from the same subjects on a different measure of confidence for the same items, their own global assessment for the set of multiple estimates as a whole, showed significantly lower levels of confidence and overconfidence than their average individual assessment for items in the set. It is argued that the event and global assessments of judgment quality are fundamentally different and are affected by unique psychological processes. Finally, we discuss the implications of a difference between confidence in single and multiple estimates for confidence research and theory.