Role of optical flow field asymmetry in the perception of heading during linear motion

During linear translation through a stationary environment, the pattern of optical flow generated on each retina is symmetrical when the head is aligned with the heading, but during lateral gaze the optical flow is asymmetric. We assessed whether human subjects could use the magnitude of this asymmetry to determine the direction of heading during passive translation through a 3-D environment. When allowed to move their heads in order to look in the direction of self-motion, subjects indicated their heading precisely and accurately. When the head was locked in alignment with the misaligned body, and gaze adjustments were not allowed, responses were quite precise, but showed a large bias which increased with increasing heading angle.     

A cognitive mediation theory of task goals and human performance

A theory is proposed to explain the linkages between individual task goals and performance. Two cognitive constructs are postulated to mediate between task goals and performance:performance expectancy and performance valence. It is asserted that an individual's task goal has a positive influence on performance expectancy and a negative influence on performance valence. Performance expectancy is proposed to have a positive influence on performance while performance valence is proposed to have a negative influence on performance. Task ability is hypothesized to influence performance both directly and indirectly through its influence on performance expectancy. A laboratory experiment was designed to test the causal model proposed by the theory. A path analysis on the data from this experiment provides strong support for the model, with performance expectancy, performance valence, and task ability predicting 63% of the variance in performance on the laboratory task.     

Philosophy of medicine and other humanities: Toward a wholistic view

A less analytic and more wholistic approach to philosophy, described as ‘best overall fit’ or ‘seeing how things all hang together,’ is defended in recent works by John Rawls and Richard Rorty and can usefully be applied to problems in philosophy of medicine. Looking at sickness and its impact upon the person as a central problem for philosophy of medicine, this approach discourages a search for necessary and sufficient conditions for being sick, and instead encourages a listing of “true and interesting observations” about sickness which reflect the convergence of a number of different viewpoints. Among the relevant viewpoints are other humanities disciplines besides philosophy and the social sciences. Literature, in particular, provides insights into the meaning and the uniqueness of episodes of sickness in a way that philosophers may otherwise fail to grasp.     

Interviewer evaluations of interviewee nonverbal behavior

Personnel representatives (N = 52) were shown one of four videotaped job interviews in which the verbal content of the 16-min interview was identical, but the interviewee's nonverbal behavior was manipulated. A “low nonverbal” interviewee was defined by minimal eye contact, low energy level, lack of affect and voice modulation, and a lack of speech fluency. The “high nonverbal” interviewee demonstrated the opposite behavior on each of these components. The subjects were asked to rate the videotaped candidates on dimensions previously identified as critical in influencing a job interviewer's decisions. Nonverbal behavior was found to have a significant effect on almost every rating made by subjects in this study. After reviewing the entire 16-min interview, 23 of the 26 subjects who saw the “high nonverbal” candidate would have invited him/her for a second interview. All 26 of the subjects who saw the “low nonverbal” candidate would not have recommended a second interview.     

Mid-career change in academia: The decision to become an administrator

This study explored the reasons why professors would leave their teaching/ research occupations to begin new careers as administrators. Valence-Instrumentality-Expectancy theory of occupational preference and choice was used as a framework to examine mid-career change among professors and department chairmen at a major university. Data showed that professors' intentions to change careers and become administrators could be explained by the theory. Analyses of job characteristics demonstrated that professors who want a mid-career change are primarily attracted by the power and formal authority vested in the administrative position, while professors who prefer to remain in their career paths do so because of the autonomy it offers.     

Responding maintained under fixed-interval and fixed-time schedules of electric shock presentation

Following initial histories under a schedule of electric shock postponement, lever pressing in squirrel monkeys was maintained under fixed-interval and fixed-time schedules of electric shock presentation. No difference in either rate or pattern of responding was obtained when these schedules were presented as components of a multiple schedule. When they were presented singly for long periods of time, the fixed-interval schedule consistently maintained a higher response rate than the fixed-time schedule. The pattern of responding under both schedules was similar, typically consisting of a pause at the beginning of each interval followed by either a steady or a positively accelerating rate of responding. The results suggest that the response-shock dependency is of critical importance in the maintenance of high rates of responding under schedules of electric shock presentation, and support the general view that such responding may be conceptualized as operant behavior under control of many of the same variables that control responding under comparable schedules of food or water reinforcement.     

Tables of d′ for variable-standard discrimination paradigms

Signal detection theory (SDT) allows a bias-free measure of sensitivity, d′, to be simply estimated from discrimination data when certain conditions are met. The computation is not straightforward, however, in several popular discrimination designs, such as two- and four-interval same-different designs and the ABX design. The present tables, derived from the SDT models of Macmillan, Kaplan, and Creelman (1977), make possible the estimation of d’ from these complex discrimination designs.     

A deglitching circuit for the AA50 D/A converter

Switching transients or “glitches” are frequently encountered in signal processing applications involving digital-to-analog (D/A) conversion. A low-cost “deglitching” circuit is described and implemented for the Digital Equipment Corporation AA50 D/A converter option on the PDP-8/e minicomputer. Switching transients were eliminated using a noninverting, unity-gain sample-and-hold circuit (employing Datei System’s SHM-IC-1). Switching transients were reduced to below-noise levels across a wide range of output levels and sampling rates.