Rationality and indeterminate probabilities

We argue that indeterminate probabilities are not only rationally permissible for a Bayesian agent, but they may even be rationally required. Our first argument begins by assuming a version of interpretivism: your mental state is the set of probability and utility functions that rationalize your behavioral dispositions as well as possible. This set may consist of multiple probability functions. Then according to interpretivism, this makes it the case that your credal state is indeterminate. Our second argument begins with our describing a world that plausibly has indeterminate chances. Rationality requires a certain alignment of your credences with corresponding hypotheses about the chances. Thus, if you hypothesize the chances to be indeterminate, your will inherit their indeterminacy in your corresponding credences. Our third argument is motivated by a dilemma. Epistemic rationality requires you to stay open-minded about contingent matters about which your evidence has not definitively legislated. Practical rationality requires you to be able to act decisively at least sometimes. These requirements can conflict with each other-for thanks to your open-mindedness, some of your options may have undefined expected utility, and if you are choosing among them, decision theory has no advice to give you. Such an option is playing Nover and Hájek??s Pasadena Game, and indeed any option for which there is a positive probability of playing the Pasadena Game. You can serve both masters, epistemic rationality and practical rationality, with an indeterminate credence to the prospect of playing the Pasadena game. You serve epistemic rationality by making your upper probability positive-it ensures that you are open-minded. You serve practical rationality by making your lower probability 0-it provides guidance to your decision-making. No sharp credence could do both.     

Two experimental tests of trust in in‐group strangers: The moderating role of common knowledge of group membership

The role that shared group membership plays in decisions to trust others is now well established within social psychology. A close reading of this literature, however, shows that this process is often moderated by other variables. Currently, we examined one potential moderator of this process. In particular, we evaluated the role that common knowledge of a shared social group membership between self and a to‐be‐trusted stranger provides as a basis for trusting this stranger. This common knowledge emerges when the truster knows the group membership of the to‐be‐trusted other, and believes that this other also knows the group membership of the truster. In two experiments, using pre‐existing and minimal groups, we show that people are more likely to trust an in‐group member over an out‐group member under conditions of common group‐membership knowledge rather than private group‐membership knowledge (i.e. other does not know truster's group), even when they could choose not to trust anyone. The manner in which these data add to current understandings of group‐based trust in strangers is discussed. Copyright © 2011 John Wiley & Sons, Ltd.     

Reducing stereotype threat in order to facilitate learning

Recent stereotype threat research has demonstrated that negative stereotypes about women's math ability can impair their mathematical learning. This experiment extends this research by examining whether presenting “gender fair” information can reduce learning decrements (on a focal and transfer task) and if the timing of this information matters. Women (N = 140) and men (N = 60) were randomly assigned to one of four conditions: control, stereotype threat only, stereotype threat removed before learning, and stereotype threat removed after learning. Compared with women in the control condition and women who had stereotype threat removed before learning, learning and transfer were poorer for women in the stereotype threat only condition and women who had stereotype threat removed after learning but before learning assessment. Men's learning and transfer were unaffected by condition. These findings suggest that a manipulation that can reduce performance deficits can also reduce learning decrements if it is presented before learning occurs. Copyright © 2011 John Wiley & Sons, Ltd.     

The next generation: the value of reminding

In two experiments, we investigated the influence of repeated processing in the context of the generation effect. In both experiments, participants studied words once or twice. Once-studied words either were read or were generated from a definition. Twice-studied words were read both times, generated both times, or read once and generated once. Free recall was best (in order of decreasing performance) after generating twice, after generating plus reading, and finally after generating once; any generation was better than purely reading. Recognition showed a similar pattern, except that the benefit of generating twice was not as striking as in recall and that reading plus generating was just as effective as generating twice. The overall pattern of results is accounted for by a simple model in which a second encoding results in a reminding of the first encoding, and this additional encoding supports subsequent recollection. This reminding is, consequently, more effective in recall than in recognition, and it operates in accordance with the principles of transfer-appropriate processing.     

Variations in constrained retrieval

Mentally reinstating encoding operations at retrieval might improve access to memories; however, such constrained retrieval is an effortful process that may not always be used. The memory-for-foils procedure (Jacoby, Shimizu, Daniels, & Rhodes, Psychonomic Bulletin & Review 12, 852-857, 2005) infers participant-initiated mental reinstatement of encoding operations during attempts at recognition from the differential memory that accrues to foils during a test of deeply processed items versus during a test of shallowly processed items, as indicated by performance on a final recognition memory test for the foils. Experiment 1 tested whether differential memory for foils is due to the evocation of task context during recollection of neighboring old items. Experiment 2 tested whether inducing a set to respond without much effort on a prior recognition test affects the likelihood of constrained retrieval on later tests. Experiment 3 tested whether constrained retrieval is less likely to occur when the deep versus shallow source of test items is intermixed, rather than blocked in separate tests. These experiments provide evidence that people query memory by mentally reinstating encoding operations and identify conditions that affect the probability of constrained retrieval.     

Multi-wave Prospective Examination of the Stress-Reactivity Extension of Response Styles Theory of Depression in High-Risk Children and Early Adolescents

The current study tested the stress-reactivity extension of response styles theory of depression (Nolen-Hoeksema Journal of Abnormal Psychology 100:569–582, 1991) in a sample of high-risk children and early adolescents from a vulnerability-stress perspective using a multi-wave longitudinal design. In addition, we examined whether obtained results varied as a function of either age or sex. During an initial assessment, 56 high-risk children (offspring of depressed parents; ages 7–14) completed measures assessing rumination and depressive symptoms. Children were subsequently given a handheld personal computer which signalled them to complete measures assessing depressive symptoms and negative events at six randomly selected times over an 8-week follow-up interval. In line with hypotheses, higher levels of rumination were associated with prospective elevations in depressive symptoms following the occurrence of negative events. Sex, but not age, moderated this association. Rumination was more strongly associated with elevations in depressive symptoms following the occurrence of negative events in girls than in boys.     

Improving Working Memory in Children with Attention-Deficit/Hyperactivity Disorder: The Separate and Combined Effects of Incentives and Stimulant Medication

Working memory (WM) is considered a core deficit in Attention-Deficit/ Hyperactivity Disorder (ADHD), with numerous studies demonstrating impaired WM among children with ADHD. We tested the degree to which WM in children with ADHD was improved by performance-based incentives, an analog of behavioral intervention. In two studies, WM performance was assessed using a visuo-spatial n-back task. Study 1 compared children (ages 9-12?years) with ADHD-Combined type (n?=?24) to a group of typically developing (TD) children (n?=?32). Study 1 replicated WM deficits among children with ADHD. Incentives improved WM, particularly among children with ADHD. The provision of incentives reduced the ADHD-control group difference by approximately half but did not normalize WM. Study 2 examined the separate and combined effects of incentives and stimulant medication among 17 children with ADHD-Combined type. Both incentives and a moderate dose of long-acting methylphenidate (MPH; ~0.3?mg/kg t.i.d. equivalent) robustly improved WM relative to the no-incentive, placebo condition. The combination of incentives and medication improved WM significantly more than either incentives or MPH alone. These studies indicate that contingencies markedly improve WM among children with ADHD-Combined type, with effect sizes comparable to a moderate dose of stimulant medication. More broadly, this work calls attention to the role of motivation in studying cognitive deficits in ADHD and in testing multifactorial models of ADHD.     

Dissociating linguistic and non-linguistic gesture processing: electrophysiological evidence from American Sign Language

A fundamental advance in our understanding of human language would come from a detailed account of how non-linguistic and linguistic manual actions are differentiated in real time by language users. To explore this issue, we targeted the N400, an ERP component known to be sensitive to semantic context. Deaf signers saw 120 American Sign Language sentences, each consisting of a “frame” (a sentence without the last word; e.g. BOY SLEEP IN HIS) followed by a “last item” belonging to one of four categories: a high-close-probability sign (a “semantically reasonable” completion to the sentence; e.g. BED), a low-close-probability sign (a real sign that is nonetheless a “semantically odd” completion to the sentence; e.g. LEMON), a pseudo-sign (phonologically legal but non-lexical form), or a non-linguistic grooming gesture (e.g. the performer scratching her face). We found significant N400-like responses in the incongruent and pseudo-sign contexts, while the gestures elicited a large positivity.     

Structural salience and the nonaccidentality of a gestalt

We perceive structure through a process of perceptual organization. Here we report a new perceptual organization phenomenon-the facilitation of visual grouping by global curvature. Observers viewed patterns that they perceived as organized into collections of curves. The patterns were perceptually ambiguous such that the perceived orientation of the patterns varied from trial to trial. When patterns were sufficiently dense and proximity was equated for the predominant perceptual alternatives, observers tended to perceive the organization with the greatest curvature. This effect is tantamount to visual grouping by maximal curvature and thus demonstrates an unprecedented effect of global structure on perceptual organization. We account for this result with a model that predicts the perceived organization of a pattern as function of its nonaccidentality, which we define as the probability that it could have occurred by chance. Our findings demonstrate a novel relationship between the geometry of a pattern and the visual salience of global structure.     

Human sensitivity to the magnitude and probability of a continuous causal relation in a video game

Continuous causation, in which incremental changes in one variable cause incremental changes in another, has received little attention in the causal judgment literature. A video game was adapted for the study of continuous causality in order to examine the novel cues to causality that are present in these paradigms. The spatial proximity of an object to an "enemy detector" produced auditory responses as a function of the object's proximity. Participants' behavior was a function of the range of the effect's auditory sensitivity and the moment-to-moment likelihood of detection. This new paradigm provides a rich platform for examining the cues to causation encountered in the learning of continuous causal relations.