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.     

Moral Individualism,Moral Relationalism,and Obligations to Non‐human Animals

Moral individualists like Jeff McMahan and Peter Singer argue that our moral obligations to animals, both human and non‐human, are grounded in the morally salient capacities of those animals. By contrast, what might be called moral relationalists argue that our obligations to non‐human animals are grounded in our relationship to them. Moral relationalists are of various kinds, from relationalists regarding assistance to animals, such as Clare Palmer and Elizabeth Anderson, to relationalists grounded in a Wittgensteinian view of human practice, such as Cora Diamond and Alice Crary. This article argues that there are, in fact, two distinct types of moral reasons, those based on salient capacities and those based on relationships. Neither type of reason is reducible to the other, and there is no third type to which to reduce them both. Any attempt at reduction would run counter to deep intuitions about our moral relation to non‐human animals as well as to other humans. Among the implications of this is that certain kinds of arguments, such as the argument from marginal cases, seem to be incomplete precisely because they do not capture the complexity of our moral relations to non‐human animals.