PET AS PART OF AN INTERDISCIPLINARY APPROACH TO UNDERSTANDING PROCESSES INVOLVED IN READING

Abstract— Positron emission tomography (PET) is a recently developed technology that can be used to create images of brain blood flow, which is related to brain activity. By acquiring images of brain blood flow during different task conditions, investigators can isolate activity changes related to specific types of information processing. Several examples demonstrate how regions involved in reading can be identified, and how the results are most interpretable when information from other disciplines is considered.     

The Effect of Punishment Probability on Overconsumption and Stealing in a Simulated Commons1

In laboratory simulations of the commons dilemma, overconsumption depletes the shared resource, whereas allowing the players to steal from each other helps preserve the resource since players take from each other rather than from the central supply. In this study, we factorially crossed three levels of punishment probability for overconsumption (0%, 25%, 75%) with three levels of probability of punishment for stealing (0%, 25%, 75%). Subjects (n= 270) in three-person groups harvested points from a slowly regenerating central pool. Results indicated that punishment of overconsumption decreased overconsumption, increased stealing, and helped preserve the commons, whereas punishment of stealing decreased stealing, increased overconsumption, and facilitated depletion of the commons. Rather than punishment of one selfish behavior suppressing the other selfish behavior, a compensatory effect occurred: Punishment of one behavior increased the occurrence of the selfish alternative.     

The effect of exposure duration on visual character identification in single, whole, and partial report

The psychometric function of single-letter identification is typically described as a function of stimulus intensity. However, the effect of stimulus exposure duration on letter identification remains poorly described. This is surprising because the effect of exposure duration has played a central role in modeling performance in whole and partial report (Shibuya & Bundesen, 1988). Therefore, we experimentally investigated visual letter identification as a function of exposure duration. We compared the exponential, the gamma, and the Weibull psychometric functions, all with a temporal offset included, as well as the ex-Gaussian, the log-logistic, and finally the squared-logistic, which is a psychometric function that to our knowledge has not been described before. The log-logistic and the squared-logistic psychometric function fit well to experimental data. Also, we conducted an experiment to test the ability of the psychometric functions to fit single-letter identification data, at different stimulus contrast levels; also here the same psychometric functions prevailed. Finally, after insertion into Bundesen's Theory of Visual Attention (Bundesen, 1990), the same psychometric functions enable closer fits to data from a previous whole and partial report experiment.     

Measuring and modeling attentional dwell time

Attentional dwell time (AD) defines our inability to perceive spatially separate events when they occur in rapid succession. In the standard AD paradigm, subjects should identify two target stimuli presented briefly at different peripheral locations with a varied stimulus onset asynchrony (SOA). The AD effect is seen as a long-lasting impediment in reporting the second target, culminating at SOAs of 200?C500?ms. Here, we present the first quantitative computational model of the effect??a theory of temporal visual attention. The model is based on the neural theory of visual attention (Bundesen, Habekost, & Kyllingsb?k, Psychological Review, 112, 291?C328 2005) and introduces the novel assumption that a stimulus retained in visual short-term memory takes up visual processing-resources used to encode stimuli into memory. Resources are thus locked and cannot process subsequent stimuli until the stimulus in memory has been recoded, which explains the long-lasting AD effect. The model is used to explain results from two experiments providing detailed individual data from both a standard AD paradigm and an extension with varied exposure duration of the target stimuli. Finally, we discuss new predictions by the model.     

Exploring the Intersecting Health Risks of Substance Abuse,Sexual Risk,and Violence for Female South African Teen Dropouts

The study sought to better understand the cultural contexts of the risks for adolescent females who have dropped out of school. Focus groups were conducted with 37 Black and Coloured females aged 13 to 17 in Cape Town, South Africa. Data were analysed using content analysis. Methamphetamine, cannabis, and alcohol were used by both, however, Black teens also used methaqualone and Coloured teens used heroin and ecstasy. Some teens traded sex for drugs and others did so at the request of their drug-addicted mothers. Teens revealed high rates of violence, including rape, and many myths and barriers about condom use, revealing risky sex behaviours. Conclusion—Cultural nuances between the two groups will help inform the adaptation of an HIV prevention intervention.     

Development of a telephone-based intervention for support persons to help smokers quit

This study represents the first step toward systematic behavioral treatment development and pilot testing of a novel approach to smoking cessation that utilizes adults interested in helping someone to stop smoking (i.e., support persons) as the agent of change. The counselor manual for a telephone-based intervention for support persons was developed based on a previous clinic-based intervention. Social cognitive theory served as the conceptual basis for the intervention. Ten adult non-smoking females completed the treatment protocol, consisting of six 20 - 30-min sessions and written materials. The support person was the sole recipient of the professional intervention. Feedback was obtained from 8 of the 10 participants and all 4 telephone counselors 1 week post-treatment (week 10). Results indicate that the telephone-based intervention was feasible and acceptable to participants. The intervention was refined based on participant and counselor feedback and will be subsequently tested in a randomized pilot trial.     

Mathematics—a Critical Filter for STEM-Related Career Choices? A Longitudinal Examination among Australian and U.S. Adolescents

Although women have made progress in entering scientific careers in biology, they remain underrepresented in mathematically intensive fields such as physics. We investigated whether gender differences in mathematics motivation and socialisers’ perceptions impacted choices for diverse STEM careers of varying mathematical intensity. Drawing on expectancy-value theory, we tested structural equation models in which adolescents’ preferred careers related to each of physics, biology, chemistry, and mathematics were predicted by prior mathematical performance, motivations, and mothers’ perceptions. We explored potential differences in gendered processes of influence using multigroup models. Samples were 331 Australian adolescents followed from 9th to 11th grade in 1998 and 277 U.S. adolescents from 9th to 12th grade in 2009–10. In both samples female adolescents preferred biological careers more than males did; male adolescents preferred physics-related careers and also mathematical careers in the Australian sample. Mothers’ perceptions were important to female and male adolescents’ mathematics motivations; gendered motivations were more evident in the Australian sample. Mathematics interest played the strongest role in male adolescents’ preferred careers, whereas actual or perceived mathematical achievements were most important for females, demonstrating the impacts of mathematical motivations on preferences for diverse STEM careers.