The World-Wide Web as a medium for psychoacoustical demonstrations and experiments: Experience and results

The World-Wide Web provides an inviting opportunity to reach large numbers of people, both as an audience for psychoacoustical discussions and demonstrations and as subjects for psychoacoustical experiments. Such use of the Web poses a unique set of challenges. We present the methodologies used to prepare a multimedia primer in auditory perception at McGill University. As well as instructional material, this primer includes acoustical experiments conducted over the Web. We discuss the response and experiences with this site in general and in a particular class situation at Hanover College.     

Signal-processing software for teaching and research in psychoacoustics under UNIX and X-Windows

A package of software is described that generates, analyzes, stores, and displays sampled waveforms. The package is designed for use under UNIX and includes C source code, UNIX manual pages, and tutorial documents. The programs interact via UNIX pipes using an ASCII-text data format, which enables the user to view the data in numerical form as well as through the use of plotting programs. Among many other functions, the programs can do the following: efficiently generate linearphase FIR filters with arbitrary transfer functions; generate impulse responses for rectangular rooms of specified dimensions; convolve waveforms with each other; perform Fourier transformation and inverse Fourier transformation; filter waveforms in the Fourier domain; filter waveforms according to the peripheral frequency selectivity of the human auditory system; cross-correlate waveforms; autocorrelate waveforms; synthesize complex waveforms, including vowel sounds and white noise. The software can read and write a variety of commonly used waveform file formats. The data can be plotted on an X-Window display using thegnuplot software, which has been included in the package. The complete software package is available via anonymous ftp from ftp.ihr.mrc.ac.uk in ~ftp/pub/johncu/wave.tar.Z     

Counseling and screening for cystic fibrosis in patients with congenital bilateral absence of the vas deferens: Patient perceptions

Congenital bilateral absence of the vas deferens (CBAVD) occurs in approximately 1.3% of infertile males and is thought to be, in most cases, a primarily genital form of cystic fibrosis (CF). Fourteen males with CBAVD considering microsurgical sperm aspiration from the epididymis (MESA) and in vitro fertilization were seen for genetic counseling and screening for CF. To retrospectively evaluate these patients' perceptions of the counseling and screening information, we conducted structured telephone interviews to assess their recall of information about CF and its impact on their health concerns and reproductive plans. We found that, as the health implications of CF are abstract and not as important to patients as the diagnosis of CBAVD itself, patients tend to view their CF status primarily in terms of their reproductive potential. Retrospective analysis afforded us an opportunity to identify the psychosocial issues of most concern to this unique patient population.     

Psychology and mind-body segregation: Are we part of the problem?

Despite advances in behavioral medicine and health psychology, the health care system and medical education continue to show resistance to a truly biopsychosocial model of medical practice. Psychologists in medical settings have generally been identified as challenging the concept of mind-body duality and the segregation of biologic and psychosocial sciences in medicine. However, examples are presented of how psychologists contribute to and perpetuate mind-body segregation via exclusive theoretical conceptualizations, arbitrary definitions of professional behavior, and dogmatic constraints on the limits of psychology's field of knowledge.     

On the time course of negative priming: Another look

In two experiments, the pattern of persistence of negative priming effects across delay intervals of 500 and 2,500 msec was assessed using a within-subjects, random sequencing of delays. Neill and Valdes (1992; Neill, Valdes, Terry, & Gorfein, 1992) have argued that a within-subject experimental design is required for decay of negative priming to be seen, in contrast to results reported elsewhere (e.g., Tipper, Weaver, Cameron, Brehaut, & Bastedo, 1991) showing stable negative priming effects across delays. In neither experiment was substantial evidence of decay detected, raising questions for the notion that suppression necessarily declines across brief temporal intervals and for the assertion that episodic retrieval is the sole source of negative priming.     

Objects and attributes in divided attention: Surface and boundary systems

A series of experiments investigated concurrent discriminations of surface and nonsurface attributes, including color, brightness, texture, length, location, and motion. In all cases but one, results matched those previously reported: Interference occurred when two discriminations concerned different objects, but not when they concerned the same one. In the two-object case, interference was the same whether discriminations were similar (e.g., two surface discriminations) or different (e.g., one surface, one boundary). Such results support a model of visual attention in which separate visual subsystems are coordinated, converging to work on surface and boundary properties of the same selected object. A partial exception is color: For reasons that are unclear, color escapes twoobject interference except from other, concurrent surface discriminations     

Control of fixation duration in a simple search task

To obtain insight into the control of fixation duration during visual search, we had 4 subjects perform simple search tasks in which we systematically varied the discriminability of the target. The experiment was carried out under two conditions. Under the first condition (blocked), the discriminability of the target was kept constant during a session. Under the second condition (mixed), the discriminability of the target varied per trial. Under the blocked condition, fixation duration increased with decreasing discriminability. For 2 subjects, we found much shorter fixation durations in difficult trials with the mixed condition than in difficult trials with the blocked condition. Overall, the subjects fixated the target, continued to search, and then went back to the target in 5%–55% of the correct trials. In these trials, the result of the analysis of the foveal target was not used for preparing the next saccade. The results support a preprogramming model of the control of fixation duration. In a simple search task, control of fixation duration appears to be indirect.     

The visual perception of rigid motion from constant flow fields

Four experiments investigated observers’ judgments of rigidity for different types of optical motion. The depicted structural deformations were of two types: (1) those with nonparallel image trajectories that are detectable from the first-order spatiotemporal relations between pairs of views; and (2) those with parallel image trajectories that can only be detected from higher order relations among three or more views. Patterns were composed of smooth flow fields in Experiments 1 and 3, and of wire frame figures in Experiments 2 and 4. For both types of display, the nonrigidity detectable from the first-order spatiotemporal structure of the motion sequence was much more salient than the deformation detectable only from the higher order spatiotemporal structure. These results indicate that observers’ judgments of rigidity are based primarily on a two-view analysis, but that some useful information can be obtained under appropriate circumstances from higher order spatiotemporal relations among three or more views.