A computational model of fractionated conflict-control mechanisms in task-switching

A feature of human cognition is the ability to monitor and adjust one's own behavior under changing circumstances. A dynamic balance between controlled and rapid responding is needed to adapt to a fluctuating environment. We suggest that cognitive control may include, among other things, two distinct processes. Incongruent stimuli may drive top-down facilitation of task-relevant responses to bias performance toward exploitation vs. exploration. Task or response switches may generally slow responses to bias toward accuracy vs. speed and exploration vs. exploitation. Behavioral results from a task switching study demonstrate these two distinct processes as revealed by higher-order sequential effects. A computational model implements the two conflict-control mechanisms, which allow it to capture many complex and novel sequential effects. Lesion studies with the model demonstrate that the model is unable to capture these effects without the conflict-control loops and show how each monitoring component modulates cognitive control. The results suggest numerous testable predictions regarding the neural substrates of cognitive control.     

Anhedonia, Emotional Numbing, and Symptom Overreporting in Male Veterans with PTSD

We used measures of positive affect and emotional expression to distinguish and better understand veterans with PTSD with symptom overreporting presentation styles. Based on prior research, symptom overreporting was defined as scores greater than eight on the F(p) (Infrequency-Psychopathology) scale of the Minnesota Multiphasic Personality Inventory-2 (MMPI-2). Data were drawn from an archival dataset of 227 combat veteran outpatients. Results were consistent with theory and research on the distinction between negative and positive affect. Major findings indicated that (a) veterans endorsing greater anhedonia had a greater likelihood of being classified as a symptom overreporter (controlling for PTSD symptoms), and (b) compared to non-symptom overreporting veterans, overreporters showed greater congruency in their presentation of diminished positive affect and their expression across self- and clinician-ratings. Our data suggest that diminished positive emotions and their behavioral expression are uniquely associated with veterans' psychological experiences, providing insight into the nature of symptom overreporters.     

Within-category discontinuity interacts with verbal rule complexity in perceptual category learning

A test of the predicted interaction between within-category discontinuity and verbal rule complexity on information-integration and rule-based category learning was conducted. Within-category discontinuity adversely affected information-integration category learning but not rule-based category learning. Model-based analyses suggested that some information-integration participants improved performance by recruiting more "units" in the discontinuous condition. Verbal rule complexity adversely affected rule-based category learning but not information-integration category learning. Model-based analyses suggested that the rule based effect was on both decision criterion learning and variability in decision criterion placement. These results suggest that within-category discontinuity and decision rule complexity differentially impact information-integration and rule-based category learning and provide information regarding the detailed processing characteristics of these two proposed category learning systems.     

Risk‐taking and the adolescent brain: who is at risk?

Relative to other ages, adolescence is described as a period of increased impulsive and risk-taking behavior that can lead to fatal outcomes (suicide, substance abuse, HIV, accidents, etc.). This study was designed to examine neural correlates of risk-taking behavior in adolescents, relative to children and adults, in order to predict who may be at greatest risk. Activity in reward-related neural circuitry in anticipation of a large monetary reward was measured with functional magnetic resonance imaging, and anonymous self-report ratings of risky behavior, anticipation of risk and impulsivity were acquired in individuals between the ages of 7 and 29 years. There was a positive association between accumbens activity and the likelihood of engaging in risky behavior across development. This activity also varied as a function of individuals' ratings of anticipated positive or negative consequences of such behavior. Impulsivity ratings were not associated with accumbens activity, but rather with age. These findings suggest that during adolescence, some individuals may be especially prone to engage in risky behaviors due to developmental changes in concert with variability in a given individual's predisposition to engage in risky behavior, rather than to simple changes in impulsivity.     

Her heart is in the right place: an investigation of the ‘heartbeat hypothesis’ as an explanation of the left side cradling preference in a mother with dextrocardia

A majority of mothers, whether right- or left-handed, exhibit a preference to hold their babies to the left of the body midline. One of the earliest explanations for this finding proposed that babies were being held close to the mother's heart [Salk, L. (1960). World Mental Health, 12 , 168–175]. Salk suggested that the foetus becomes imprinted on the sound of the maternal heartbeat in utero. This paper reports a left holding preference in a mother who has the heart positioned on the right rather than the normal left side of the body. Salk's ‘heartbeat hypothesis’ is not supported by the holding preference of the dextrocardiac mother, nor by the detailed patterns of holding in the control group. © 1998 John Wiley & Sons, Ltd.     

The Basic Goods Theory and Revisionism: A Methodological Comparison on the Use of Reason and Experience as Sources of Moral Knowledge

In Roman Catholic moral theology there is an ongoing debate between the proportionalist or revisionist school and the traditionalist school that has developed what is referred to as the ‘New Natural Law Theory’ or ‘Basic Goods Theory’ (BGT). The stakes in this debate have been raised with Pope John Paul II's encyclical Veritatis Splendor (1993) on fundamental moral theology that condemned ‘proportionalism’ or ‘teleologism’ as an ethical theory while utilizing many of the ideas, concepts, and terminology of the BGT, thereby implicitly endorsing that ethical theory. While absolute norms and intrinsically evil acts have frequently been the focus of debate between these two schools, what is it that divides them fundamentally, on the level of ethical method? It is the role and function of reason and experience as two sources of moral knowledge, in part, that distinguish these two versions of natural law on the most basic level. While the BGT has a strict hierarchy of the sources of moral knowledge that posits the hierarchical magisterium as the definitive interpreter of reason and experience, revisionists posit a more dialogical relationship between reason, experience, and the magisterium. On certain ethical issues (e.g., artificial birth control), the experience of the faithful as well as the rational arguments developed by revisionist Catholic moral theologians challenge some of the normative claims of the magisterium. This paper investigates the methodological use of reason and experience in each theory's interpretation of natural law and how and why these two sources of moral knowledge lead to fundamentally divergent normative claims on particular ethical issues.