Affective personality differences in neural processing efficiency confirmed using fMRI

To test for a relation between individual differences in personality and neural-processing efficiency, we used functional magnetic resonance imaging (fMRI) to assess brain activity within regions associated with cognitive control during a demanding working memory task. Fifty-three participants completed both the self-report behavioral inhibition sensitivity (BIS) and behavioral approach sensitivity (BAS) personality scales and a standard measure of fluid intelligence (Raven’s Advanced Progressive Matrices). They were then scanned as they performed a three-back working memory task. A mixed blocked/ event-related fMRI design enabled us to identify both sustained and transient neural activity. Higher BAS was negatively related to event-related activity in the dorsal anterior cingulate, the lateral prefrontal cortex, and parietal areas in regions of interest identified in previous work. These relationships were not explained by differences in either behavioral performance or fluid intelligence, consistent with greater neural efficiency. The results reveal the high specificity of the relationships among personality, cognition, and brain activity. The data confirm that affective dimensions of personality are independent of intelligence, yet also suggest that they might be interrelated in subtle ways, because they modulate activity in overlapping brain regions that appear to be critical for task performance.     

The psychometric function: I. Fitting, sampling, and goodness of fit

The psychometric function relates an observer’s performance to an independent variable, usually some physical quantity of a stimulus in a psychophysical task. This paper, together with its companion paper (Wichmann & Hill, 2001), describes an integrated approach to (1) fitting psychometric functions, (2) assessing the goodness of fit, and (3) providing confidence intervals for the function’s parameters and other estimates derived from them, for the purposes of hypothesis testing. The present paper deals with the first two topics, describing a constrained maximum-likelihood method of parameter estimation and developing several goodness-of-fit tests. Using Monte Carlo simulations, we deal with two specific difficulties that arise when fitting functions to psychophysical data. First, we note that human observers are prone to stimulus-independent errors (orlapses). We show that failure to account for this can lead to serious biases in estimates of the psychometric function’s parameters and illustrate how the problem may be overcome. Second, we note that psychophysical data sets are usually rather small by the standards required by most of the commonly applied statistical tests. We demonstrate the potential errors of applying traditionalX ² methods to psychophysical data and advocate use of Monte Carlo resampling techniques that do not rely on asymptotic theory. We have made available the software to implement our methods.     

Low target prevalence is a stubborn source of errors in visual search tasks

In visual search tasks, observers look for targets in displays containing distractors. Likelihood that targets will be missed varies with target prevalence, the frequency with which targets are presented across trials. Miss error rates are much higher at low target prevalence (1%-2%) than at high prevalence (50%). Unfortunately, low prevalence is characteristic of important search tasks such as airport security and medical screening where miss errors are dangerous. A series of experiments show this prevalence effect is very robust. In signal detection terms, the prevalence effect can be explained as a criterion shift and not a change in sensitivity. Several efforts to induce observers to adopt a better criterion fail. However, a regime of brief retraining periods with high prevalence and full feedback allows observers to hold a good criterion during periods of low prevalence with no feedback.     

Working memory,math performance,and math anxiety

The cognitive literature now shows how critically math performance depends on working memory, for any form of arithmetic and math that involves processes beyond simple memory retrieval. The psychometric literature is also very clear on the global consequences of mathematics anxiety. People who are highly math anxious avoid math: They avoid elective coursework in math, both in high school and college, they avoid college majors that emphasize math, and they avoid career paths that involve math. We go beyond these psychometric relationships to examine the cognitive consequences of math anxiety. We show how performance on a standardized math achievement test varies as a function of math anxiety, and that math anxiety compromises the functioning of working memory. High math anxiety works much like a dual task setting: Preoccupation with one’s math fears and anxieties functions like a resource-demanding secondary task. We comment on developmental and educational factors related to math and working memory, and on factors that may contribute to the development of math anxiety.     

Predicting short-term outcome in well-being following suicidal behaviour: the conjoint effects of social perfectionism and positive future thinking

This study investigated an integrative, psychological model of suicidality involving the relationship between perfectionism and future thinking to predict short-term outcome in well-being following a suicidal episode. Two hundred and sixty-seven adults hospitalized following a self-harm episode completed a range of clinical and psychological measures in hospital and were followed up approximately two months after discharge. Hierarchical regression analyses confirmed that, among the suicidal self-harmers who had a history of repetitive self-harm (n=65), outcome among low social perfectionists changed as a function of positive future thinking such that outcome was better for those high on positive thoughts compared with those low on positive future thoughts. There was no such positive change in outcome among the high social perfectionists. There were also no significant interactive effects evident among the non-repetitive self-harmers (n=61). These findings extend recent research to suggest that socially prescribed perfectionism and positive future thinking (but not negative future thinking) are implicated in outcome following repetitive suicidality. Implications for theory and clinical practice are discussed.     

Reward sensitivity and substance abuse in middle school and high school students

In this study, the authors investigated the relation between reward and punishment sensitivity and adolescent substance use. The sample (N = 216; 130 girls, 85 boys) was drawn from high school and middle school students enrolled in a Midwestern suburban school district. Participants completed a substance use questionnaire and the Sensitivity to Punishment and Sensitivity to Reward Questionnaire (R. Torrubia, C. Avila, J. Molto, & X. Caseras, 2001). For 13 of 15 types of substance abuse, students with high reward sensitivity and low punishment sensitivity showed the highest levels of use. This finding supports the hypothesis of an interaction effect between reward sensitivity and punishment sensitivity and suggests that individuals who are high in reward sensitivity but low in sensitivity to punishment may be at a higher risk for substance abuse.     

Bloch's Paradox and the Nonlocality of Chance

I show how an almost exclusive focus on the simplest case—the case of a single particle—along with the commonplace conception of the single‐particle wave function as a scalar field on spacetime contributed to the perception, first brought to light by I. Bloch, that there existed a contradiction between quantum theory with instantaneous state collapses and special relativity. The incompatibility is merely apparent since treating wave‐function values as hypersurface dependent avoids the contradiction. After clarifying confusions which fueled the perception of a paradox, I elaborate on an analysis of the wave function due to Wayne Myrvold to show that nothing special, or ad hoc, is required in treating wave‐function values, even in the single‐particle case, as hypersurface–dependent; rather, the hypersurface dependence of these values is the natural development of nonlocal entanglement in the context of the relativity of simultaneity. Properly understood, what Bloch’s paradox reveals is that the combination of nonlocal entanglement together with a hypersurface‐dependent process of state collapse conflicts with the thesis of spatiotemporal separability and, in particular, with the idea that chances are local matters of fact.     

Reconsidering Relativistic Causality

I discuss the idea of relativistic causality, i.e., the requirement that causal processes or signals can propagate only within the light‐cone. After briefly locating this requirement in the philosophy of causation, my main aim is to draw philosophers’ attention to the fact that it is subtle, indeed problematic, in relativistic quantum physics: there are scenarios in which it seems to fail.

I set aside two such scenarios, which are familiar to philosophers of physics: the pilot‐wave approach, and the Newton–Wigner representation. I instead stress two unfamiliar scenarios: the Drummond–Hathrell and Scharnhorst effects. These effects also illustrate a general moral in the philosophy of geometry: that the mathematical structures, especially the metric tensor, that represent geometry get their geometric significance by dint of detailed physical arguments.     

Interpersonal reactions to suicide attempt: the role of respondent causal attributions

Interpersonal responses to a depressed person with or without a suicide attempt were examined. It was hypothesized that the depressed person who attempted suicide would receive higher negative attributions and interpersonal rejection, and that attributions would mediate the relationship between exposure to a depressed person and rejection. Contrary to hypotheses, respondents were more willing to interact with, held higher esteem for, and endorsed lower negative attributions for the depressed person who attempted suicide. Mediation hypotheses were supported. Findings suggest that a suicide attempt may promote less negative attributions toward depressed individuals, which in turn dampen negative interpersonal reactions.     

A computational model of event segmentation from perceptual prediction

People tend to perceive ongoing continuous activity as series of discrete events. This partitioning of continuous activity may occur, in part, because events correspond to dynamic patterns that have recurred across different contexts. Recurring patterns may lead to reliable sequential dependencies in observers' experiences, which then can be used to guide perception. The current set of simulations investigated whether this statistical structure within events can be used 1) to develop stable internal representations that facilitate perception and 2) to learn when to update such representations in a self-organizing manner. These simulations demonstrate that experience with recurring patterns enables a system to accurately predict upcoming stimuli within an event, to identify boundaries between such events based on transient increases in prediction error, and to use such boundaries to improve prediction about subsequent activities.