Temporal brightness enhancement: Studies of individual differences

We have previously identified categorical individual differences in the occurrence of temporal brightness enhancement (TBE) by using a simultaneous brightness discrimination paradigm (Bowen & Markell, 1980).TBE is a nonmonotonic relation between brightness and pulse duration, pulses of intermediate duration (75–125 msec) can appear brighter than longer or shorter pulses of the same luminance. Three classes of observers can be defined based on whether they perceive TBE under one of two conditions of temporal asynchrony between a short test pulse and a longer (500 msec) comparison pulse:simultaneous onset of the pulses orsimultaneous offset. Type A observers show TBE for both asynchrony conditions; Type B observers show the effect for simultaneous offset but not simultaneous onset; Type C observers do not show TBE for either asynchrony. In the present study, we show that Type A and Type C observers maintain a constant brightness-duration relation as the asynchrony between test and comparison pulses is varied from simultaneous onset to simultaneous offset. Type B observers show a gradual shift in the brightness-duration relation as asynchrony changes. In a separate experiment, we find that practice has little effect on Type A and Type B observers but that Type C observers may change in classification to Types A and B over as few as five experimental sessions. The hypothesis that individual differences are due to differential “weighting” of chromatic (sustained) and achromatic (transient) visual channels is discussed.     

Sex differences in psychological effects of exercise

The purpose of this study was to investigate sex differences in psychological effects of exercise on university students. University students (73 female and 65 male) were randomly assigned to experimental and control groups by equating sex in each group. The experimental group participated in step dance sessions of 50 min per day, 3 days per week for 10 weeks with 60-80% of their heart rate reserves. Throughout the 10-week period, the lecture control group was told not to participate in any organized or structured exercise and participated in a lecture that was about the physiological and psychological benefits of exercise. Self-concept, belief in external control, and trait anxiety of the groups were measured before and after the exercise program. A significant improvement in the psychological variables after the exercise program and more improvement for female exercise participants were expected. Analysis revealed no significant initial differences in self-concept, belief in external control, and trait anxiety between the two groups or between males and females, other than family and moral/ethical self. Repeated measures analysis of variance revealed that exercise led to less belief in external control and significant improvement in physical self and identity dimensions of self-concept for the experimental group compared to the control group. However, there was no significant difference in trait anxiety between the two groups after exercise (p>.05). Analysis also revealed that changes in belief in external control, trait anxiety, and self-concept did not differ with regard to sex. Males and females showed no difference in their improvement on trait anxiety, belief in external control, and most dimensions of self-concept during the 10 weeks. Only changes in personal and physical self throughout 10-week period were different for males and females. Exerciser males improved their personal self and physical self scores more than female exercisers and male and female nonexercisers throughout the 10-week period (p<.05).     

Patterns of continuity: a dynamic model for conceptualizing the stability of individual differences in psychological constructs across the life course

In contemporary psychology there is debate over whether individual differences in psychological constructs are stable over extended periods of time. The authors argue that it is impossible to resolve such debates unless researchers focus on patterns of stability and the developmental mechanisms that may give rise to them. To facilitate this shift in emphasis, they describe a formal model that integrates 3 developmental processes: stochastic-contextual processes, person-environment transactions, and developmental constancies. The theoretical and mathematical analyses indicate that this model makes novel predictions about the way in which test-retest correlations are structured across a wide range of ages and test-retest intervals. The authors illustrate the utility of the model by comparing its predictions against meta-analytic data on Neuroticism. The discussion emphasizes the value of focusing on patterns of continuity, not only as phenomena to be explained but as data capable of clarifying the developmental processes underlying stability and change for a variety of psychological constructs.     

On the relationship between the psychological environment and the development of individual differences in abilities

Some previous attempts at dimensionalizing human psychological environments are briefly considered. The problem is reformulated within the context of the development of dimensions of individual differences in abilities. The human psychological environment is viewed within the context of general systems theory. The latter permits an integrated view with respect to dimensions of the psychological environment and dimensions of individual differences within a developmental context. Critical in this formulation is the idea that, within the framework of the development of individual differences, it is of value to postulate the dimensions of the psychological environment as isomorphic to dimensions of individual differences.     

Kinesthetic aftereffects and individual differences in carryover effects

Prior research has found that individual differences in long-lasting carryover effects occur in the kinesthetic aftereffect (KAE) task both when the aftereffect inducing block was wider (I greater than T) and narrower (I less than T) than the test block. The present study found that such individual differences in carryover effects also occur for a no-aftereffect-induction control condition, with a magnitude approximately equal to that found for the I greater than T and I less than KAE variants used here.     

Trial distinctiveness in visuospatial working memory: effects on individual differences

ABSTRACT

Previous research has shown that proactive interference (PI) negatively affects performance on working memory (WM) tasks, particularly when to-be-remembered items are similar across trials, and that individuals with low WM spans are more susceptible to PI than those with high spans. The two experiments of the present study further explored individual differences in susceptibility to PI in the visuospatial domain. The similarity of the to-be-remembered locations was manipulated across trials by varying whether locations were presented in different colours and/or accompanied by unique sounds. It was hypothesised that these manipulations would reduce PI, improving participants’ memory. In addition, because of their increased susceptibility to PI, it also was hypothesised that low spans would benefit more than high spans from increases in distinctiveness. The results of both experiments were consistent with these hypotheses, suggesting that even low-span individuals can overcome the effects of PI, given the right task support.     

Proactive interference in sentence recall: Topic-similarity effects and individual differences

The effect of topic similarity on proactive interference in sentence recall was investigated in two experiments using the Brown-Peterson paradigm. In Experiment 1, successive sentences about the same topic and related topics were both associated with substantial and progressive amounts of proactive interference; however, a significant trials × condition interaction indicated that the effect was stronger in the related-topics condition. Moreover, significant negative correlations were found between individual differences in susceptibility to proactive interference and academic achievement test scores. In Experiment 2, relatively weak effects leveling off on the second trial were obtained with sentences about unrelated topics. With some assumptions about the spread of activation during retrieval, the results were attributed to response-set interference. The practical implications of these data were also considered, and it was suggested that proactive interference might be a common cause of learning problems.     

Imageability effects in word naming: an individual differences analysis.

The present research was designed to extend research by Strain, Patterson, and Seidenberg (1995) who found that imageability facilitates naming of low-frequency irregular words. Experiment 1 shows that the impact of imageability on word naming varies with phonological coding skill. In Experiment 2, the effect of imageability on naming low-frequency irregular words was shown to occur across an extended set of items. Together, the present findings support the notion that semantics may play a role in phonological coding when the mappings between orthography and phonology are weak.     

The psychological contract and individual differences: The role of exchange and creditor ideologies

The present study examines exchange and creditor ideologies (two dispositional characteristics that are strongly related to exchange relationships) and their moderating effects on the psychological contract. Five hundred public-sector employees were studied over a 3-year period. Respondents’ were surveyed as to their perceptions of what they believed their employer owed them (e.g., job security, training, involvement in decision making, etc.) and the extent to which these “employer obligations” had been met. In addition, we assessed respondents’ perceptions of their own obligations to their employer (e.g., agreeing to work extra hours, volunteering for non-job-related activities, working unpaid hours, etc.) and the extent to which they believed that these “employee obligations” had been fulfilled. The results indicate that creditor ideology related positively to employee perceptions of their obligations to the employer and the extent to which they fulfilled those obligations while exchange ideology related negatively to employee obligations and fulfillment of obligations. Exchange ideology moderated the effects of perceived employer obligations on employee obligations and fulfillment of obligations while creditor ideology moderated the relationship between perceived employer fulfillment of obligations and employee obligations. This article provides preliminary evidence to the benefits of examining the role of individual dispositions in psychological contract research—a previously neglected topic—and discusses the potential implications for the practice of management.     

Decision framing: moderating effects of individual differences and cognitive processing

Two studies examined the effect of an individual difference variable, need for cognition (NC), and processing of the options on the occurrence of risky choice framing effects. In Study 1 (N=206), frame interacted with NC and math skill such that no framing effect was observed among those high in both NC and math skill. No effect was found for the processing manipulation of requesting a reason for one's choices. Study 2 (N=257) enhanced the processing of the problems by asking participants to write out the options as they would describe them to a friend. Results showed that frame interacted with NC and depth of processing such that no framing effect was observed among those high in NC who were in the deep processing condition. These findings suggest that NC and depth of processing need to be considered in concert in order to understand their moderating effects on framing. Copyright © 2004 John Wiley & Sons, Ltd.