Visual hemispheric asymmetries depend on which spatial frequencies are task relevant

Observers classified sine-wave and square-wave gratings on the basis of fundamental frequency (Are the bars wide or narrow?) or on the basis of higher harmonic frequencies (Are the bars sharp or fuzzy?). Stimuli were presented in either the left (LVF) or right (RVF) visual field. When the classification was made on the basis of the fundamental frequencies (1 or 3 c/deg), there was a LVF/right hemisphere advantage. However, when the classification was on the basis of a sharp/fuzzy distinction which involved searching for the higher harmonic frequencies, then a RVF/left hemisphere advantage was found.     

Picture Perception Lab: A program for picture perception experiments on the Macintosh II

Picture Perception Lab (PPL) is a program for picture perception experiments. PPL capitalizes on the sophisticated drawing software available for the Macintosh computer by allowing the user to create stimulus images by using almost any drawing package. Through a series of user-friendly dialog boxes, PPL enables even nonprogrammers to develop, quickly and easily, tachistoscopelike vision experiments. The program allows a wide variety of experimental designs. Image exposure durations and subjects’ reaction times are precisely monitored with millisecond timing functions. Each image is drawn on the screen in a single 60-Hz refresh.     

The linkage between stimulus frequency and covert peak areas as it relates to monaural localization

Head-related transfer functions for differently centered narrow noise bands were obtained on 6 subjects. Derived from these measurements were covert peak areas (CPAs), defined as the spatial constellation of loudspeakers that generates maximal sound pressure at the entrance of the ear canal for specific bands of frequency. On the basis of previous data, we proposed that different frequency bands served as important spectral cues for monaural localization of sounds from different loci and that location judgments were directed toward the CPAs associated with the different bands. In the first study, the stimuli were bandpass filtered so that they contained only those frequencies whose associated CPAs occupied either the monaural listener’s “upper” or “lower” spatial regions. Loudspeakers, separated by 15°, were stationed in the left hemifield, ranging from 0° to 180° azimuth and ?45° to 60° elevation. Subjects reported the loudspeaker from which the sound appeared to originate. Judgments of the sound’s elevation were in general accord with the CPAs associated with the different frequency segments. In the second study, monaural localization tests were administered in which different 2.0-kHz-wide frequency bands linked with specific CPAs were notch filtered from a 3.5-kHz highpass noise band. For the control condition, the highpass noise was unfiltered. The data demonstrated that filtering a frequency segment linked with specific CPAs resulted in significantly fewer location responses directed toward that particular spatial region. These results demonstrate in greater detail the relation between the directional filtering properties of the pinna and monaural localization of sound.     

The differentiation of rhythmic structure

Listeners judged whether two five-tone nonmetric rhythms were the same or different. Each rhythm was presented one, two, or four times to study the process of perceptual differentiation. The results indicated that the listeners perceived these rhythms in-terms.of the grouping of the tones, and not in terms of the timing between the groups. Two rhythms that had the same perceptual grouping were judged as being identical, even if the timing between the groups was different. The perception of the groupings of tones developed gradually. If each rhythm was presented only once, then the listeners had only a global percept, focused on groups (runs) of three elements, and often judged two different rhythms as being identical. If the rhythms were presented two or four times, then the grouping of the tones became more differentiated and the listeners were less likely to judge different patterns as being identical. Thus, perception of auditory rhythmic structure appears to follow the same developmental process as the perception of visual spatial structure.     

The negative generation effect: Delineation of a phenomenon

In four experiments employing between-list designs, generation was found to have negative effects on free recall of word pairs and on cued recall of the second word. In addition, generation had negative effects on measures of word-pair integration and on clustering in recall. In contrast, positive effects of generation were found on free recall of second words alone, and on a recognition test for memory of the second word. It was concluded that in between-list designs, generation led to greater individual-item processing of the generated term than reading, but this processing occurred at the expense of processing the relation between the words in a pair and processing the relations between different pairs in a list.     

Children’s competitive behavior: A challenging alternative

The effect of challenge on the cooperative and competitive behavior of 120 urban American children was assessed using two experimental game apparatuses, one of which provided a challenging cooperative response. Significantly more cooperation was observed when the subjects were presented with a challenging cooperative response. In addition, a reliable age effect was found indicating that the older subject group (10–12 years old) was more cooperative than the younger two age groups (5–7 and 8–10 years old). Finally, a significant game condition x order interaction was discovered suggesting that under some conditions the order in which the games were played affected the degree of subject cooperation. Results are related to a theory of competence motivation. It is argued that cooperation among American children may be increased if the task involves the presence of challenge. A portion of this research was presented at the biennial meetings of the Society for Research in Child Development, Detroit, Michigan, 1983.     

A comparison of inexpensive statistical packages for microcomputers running MS-DOS

The purpose of the present paper is to describe and compare some inexpensive software packages that calculate a variety of statistics on microcomputers running MS-DOS. For each package, hardware requirements, program capabilities, limitations, accuracy, error handling, and other features are considered.     

Understanding Seat-Belt Intentions and Behavior: A Decision-Making Approach1

In an experimental study designed to investigate a decision-making model of seat-belt use, 227 employees of an agrochemical company participated in a health information program in which they watched either a videotape on seat belts or a control videotape and completed questionnaires immediately afterward and at 3 months and 1 year after exposure. In terms of total effects, the seat-belt videotape influenced beliefs, fear, and intentions assessed immediately after exposure, but had no effect on self-reported frequency of belt use at 3 months or 1 year. A full path analysis indicated some support for the decision-making model. In particular, probability difference (the perceived reduction in risk of death or serious injury due to wearing a belt) had a large influence on intentions to wear a belt and partly mediated the effect of the videotape on intentions. Reported frequency of belt use at 3 months was influenced both by post-test intentions and by initial frequency of belt use. Similarly, belt use at 1 year was affected by belt use at 3 months and by initial belt use. The findings are discussed in terms of the role of subjective probabilities and habitual factors in seat-belt use.