Comments on current ratio-setting models for time perception

This paper is concerned with the analysis and interpretation of ratio-setting data. Ratio-setting data have been used in support of the conclusion that time perception is not veridical. In the present paper, new ratio-setting data are presented and it is argued that the existing ratio-setting models do not allow the psychophysical law for time to be derived.     

Application of variable criterion theory to choice reaction time

A theory of choice reaction time ICRT is presented which is based on a variable criterion model assuming the decision criterion to be normally distributed. The theory provides functions of time describing the growth of component processes following stimulus onset. For correct responses, these processes are sensory and associative strength. For errors, the processes are sensory strength, generalized associative strength, and associative inhibition. A model for separating the effects of these processes from that of response competition is presented. The theory describes, with great accuracy, the CRT distributions of correct responses and errors, not only for the experiment for which it was derived, but also for a second experiment in which the criterion was experimentally manipulated. It accounts for the basic facts of the speed-accuracy tradeoff, not only with respect to the two experiments with different speed requirements, but also with respect to the variation of speed over trials within each experiment. While derived from group data, the theory also describes the performance of individual subjects. The mean and variability of the criterion distribution and the ability to utilize associative inhibition are identified as the major sources of individual differences. Methodological problems involved in the scaling analysis of group data are also discussed.     

Plasma glucose and insulin levels in monkeys anticipating feeding

To see whether plasma glucose or insulin changed in anticipation of feeding, we provided seven rhesus monkeys with four-hour access to food every other day. Blood was sampled before and during a 30-minute signal which ended with food availability and before and during a 30-minute signal which was not closely and reliably linked with food availability. Plasma insulin showed no evidence of conditioning. Plasma glucose was higher during the signal than prior to the signal in both experiments. This probably reflects the arousing nature of the signal rather than appetitive-associated learning. However, the differences, while statistically significant, were probably biologically trivial because they fall within the normal fluctuations of meal-fed monkeys. Under the conditions of this experiment, it appears that conditional changes in glucose and insulin do not reliably occur in monkeys anticipating access to food.     

Semantic congruity and lexical marking in symbolic comparisons: An expectancy hypothesis

Lexical marking and semantic congruity effects were investigated in four symbolic size comparison experiments. Predictions followed from an expectancy hypothesis suggested by results of recent comparative judgment studies. According to the present position, lexical marking and semantic congruity should be mutually exclusive effects in such tasks, and the demonstration of either dependent upon the order in which the stimuli and the comparative term are evaluated. When the comparative precedes the stimuli, an expectancy is created whereby the subject is more likely to be prepared for, say, large items following the comparative “larger” and small items following the comparative “smaller.” In addition, the usual advantage of unmarked as compared to marked comparisons should be offset by the initial processing of the comparative. As predicted, the comparative-stimulus presentation order produced a significant semantic congruity effect and no effect of lexical marking in Experiment 1. Conversely, when stimuli precede the comparative, or are presented simultaneously with it, no expectancy should be created, as the items are immediately available to the subject, and the semantic congruity effect should not be obtained. Upon presentation of the comparative, however, unmarked comparisons should be easier than marked comparisons. Experiments 2 and 4 confirmed these expectations, as significant lexical marking effects were obtained and significant congruity effects were not. These findings are contrary to predictions derived from a semantic coding interpretation of the symbolic comparison process.     

The perception of time

The present paper organizes and evaluates selected portions of the time perception literature. Emphasis is on data and theory concerned primarily with judgments of brief temporal intervals. Research concerning the psychophysical law for time, Weber’s law, the time-order error, and the role of nontemporal information is evaluated. This is followed by a consideration of current, quantitatively oriented, theoretical formulations for time perception.     

Children's Participation in Genetic Prevalence Research: Influences on Enrollment and Reports of Parent Satisfaction1

The present studies were designed to evaluate methodological influences on the efficiency of genetic-screening studies, specifically when enrolling preschoolers in a prevalence study of the fragile X full mutation. The studies include replication of earlier findings with school-age children, which showed that (a) a higher enrollment rate occurred when the study was introduced to a parent by a physician (73.7%) versus by a research assistant (58.7%), and (b) parents initially undecided about participating were more likely to eventually enroll if they had completed enrollment forms at the time of recruitment, In-person recruitment led to higher enrollment rates (60%) than did recruitment by mail (36.8%). Feedback from parents indicated the importance of emphasizing the optional nature of participation in screening studies.     

The resident researcher: An alternative career model centered on community

Considers the potential benefits and costs of an alternative career model for community researchers, one in which professionals specialize in the community where they live. By virtue of their local familiarity, resident researchers can make more informed judgments about research problems and methods. They can employ longitudinal designs to assess change and be available to assist in interpretation and implementation of research. Potential costs include the possibility of provincialism, unintended researcher effects, ethical dilemmas, the need to cultivate community relations, and role conflicts. Interdisciplinary training programs and research field stations can contribute to the development of the resident researcher role. Researchers in the community can help generate grass roots support for social science research. We acknowledge Louise Shedd Barker's helpful comments and suggestions on an earlier version of this article.     

Psychological Correlates of the Transmission and Acceptance of Rumors About AIDS1

The present investigation was intended to identify the emotional and cognitive factors associated with the transmission and acceptance of widely disseminated misconceptions about AIDS. A rumor questionnaire listing 10 prevalent misconceptions about AIDS was completed by 229 college students. Consistent with predictions derived from current rumor theory (Rosnow, 1980, 1988), anxiety elicited by AIDS rumors was found to be the factor most strongly related to rumor transmission. The subjects who reported having changed their behavior as a result of the AIDS crisis also were likely to transmit AIDS rumors. Regression analysis revealed that, together, personal anxiety elicited by specific rumors and behavior change represented the strongest predictors of AIDS rumor transmission (R²= .24, p < .0001). Anxiety-provoking rumors perceived as important and personally consequential were most likely to be believed (R²= .56, p < .0001). A minority of subjects (12%) reported behavior changes that actually reduce the risk of AIDS. Implications of this research for AIDS public education campaigns are discussed.     

Characteristics of the indirect McCollough effect

Induction of contingent color aftereffects with a single chromatic grid sometimes results in an illusory color on a grid different from the one presented during induction. Such illusory color, contingently elicited by a noninduced grid, has been termed the indirect McCollough effect (indirect ME). We show that the indirect ME occurs only when the color complementary to the grid color is present during induction (either physically present or as a color afterimage), and that the indirect ME is seen only on gratings that are orthogonal to the induction orientation. These findings are in accord with the account of the indirect ME proposed by Humphrey, Dodwell, and Emerson (1989). We also show that characteristics of the indirect ME (seen following one-grid induction), both on induced and orthogonal orientations, are similar to those observed with the direct ME (seen following the usual two-grid induction procedure). Both procedures result in contingent aftereffects that display substantial retention and that do not display interocular transfer.     

An investigation of neuronal integrity in severe paediatric traumatic brain injury.

Magnetic Resonance Spectroscopy (MRS) and its association with neuropsychological functioning was examined in the chronic injury phase of paediatric traumatic brain injury (TBI). Fifteen children, aged 10-16 years, with severe TBIs were compared with 15 controls, matched for age and gender. The TBI group was found to have significantly lower levels of -acetyl aspartate (NAA) and Choline (Cho) in the right frontal lobe and generally displayed reduced performances on neuropsychological tests. A correlation between metabolites and reaction times was also obtained. Findings indicate a role of proton MRS as a measure of neuronal integrity following severe paediatric TBI and suggest a potential association of MRS with specific neuropsychological impairments.