Footprints sticking out of the sand. Part 2: children's Bayesian priors for shape and lighting direction

The shading information in images that depict surfaces of 3-D objects cannot be perceived correctly unless the direction of the illuminating light source is known and, in the absence of this knowledge, perception in adults is consistent with a light-from-above Bayesian prior assumption. In order to investigate if children make use of a similar assumption, 171 children between the ages of 4.6 and 10.8 years were tested with 20 images containing shading information, where the shape depicted in each image could be perceived as either convex or concave. Each child's Bayesian prior probability that light comes from above was estimated, and (assuming that decision-noise is approximately the same in all children) regression analyses revealed a significant increase in this prior probability of 0.034-0.035 per year, and predict a neutral prior (0.5) at 1.6 years for naturalistic picture stimuli and 3.6 years for abstract symbol stimuli. Additionally, each child's prior probability for perceiving shapes as being convex/concave was estimated, and was found to be close to a neutral value of 0.5 for all ages. Together, these results indicate that children have a neutral prior for shape convexity, and that their prior probability for lighting direction gradually shifts towards an adult-like prior value as they grow older. Finally, the status of these one-dimensional priors is discussed in relation to marginal distributions of high-dimensional priors implicit in the statistical structure of the physical word.     

Risk for suicidal ideation and suicide attempts associated with co-occurring depression and conduct problems in early adolescence

This study investigates the early manifestation of co-occurring depression and conduct problems as a predictor of heightened risk for later suicidal ideation and behavior in a community sample of 521 adolescents. Self-reported symptoms of depression and conduct problems were evaluated in early 6th grade. Suicidal thoughts and behaviors were tracked through multiple assessments carried out over the middle school years. Compared to adolescents with depression symptoms only, conduct problem symptoms only, or low psychopathology, those with co-occurring depression and conduct problem symptoms had the highest risk for subsequent suicidal ideation, recurrent suicidal behaviors, and suicide attempts.     

Leader‐driven distortion of probability and payoff information affects choices between risky prospects

Research indicating that decision makers often distort new information to favor nascent preferences has focused primarily on riskless choice rather than risky choice. In addition, the critical assumption that information distortion mediates the link between the initially preferred alternative and the final choice has not been tested in a compelling manner. In an experiment designed to fill these gaps, participants made six choices involving pairs of hypothetical three‐outcome monetary gambles. We manipulated initial preferences by varying the order in which gamble features were presented. Multilevel regressions indicated that participants distorted their evaluations of precise probabilities and payoffs in the direction of their emerging preferences and that they used their biased evaluations to update those preferences. As expected, information distortion mediated the effect of initial preferences on final choices and final preference strength. In a follow‐up experiment, we compared a standard measure of information distortion (based on comparisons to mean ratings in a no‐choice control task) to a more personalized measure (based on participants' own ratings in the control task) and found the mean‐based measure to be superior for the probability and payoff information in question. Other findings in Experiment 2 corroborated the results of Experiment 1. In both studies, the distortion of quantitative inputs in a simple task highlights the non‐normative circularity of the choice process. Copyright © 2010 John Wiley & Sons, Ltd.     

Demonstrating and eliminating the aggregation effect in physical skill tasks

Confidence judgments can be elicited in multiple ways. One of these procedures is to provide confidence judgments regarding each of a number of cases (individual judgments). A second procedure is to provide confidence judgments about a set of items (an aggregate judgment). Much research has demonstrated an aggregation effect—that individual judgments are more confident than aggregate judgments—within the cognitive knowledge domain. However, this effect has not previously been investigated with physical performance skill tasks. In three experiments, participants gave individual and aggregate judgments regarding the number of successful tosses they would make in either a ring toss, ping‐pong toss, or basketball toss task. In keeping with the aggregation effect, individual judgments were more confident than were aggregate judgments of success. Additionally, we eliminated the aggregation effect in Experiments 2 and 3 by employing a case‐specific base rate manipulation. Consistent with previous research with cognitive tasks, these results suggest that individual confidence judgments for physical skill tasks are determined primarily by characteristics associated with the individual case to be judged, whereas aggregate confidence judgments are determined by a more general evaluation of one's ability in the domain. Copyright © 2009 John Wiley & Sons, Ltd.     

Chunking by colors: assessing discrete learning in a continuous serial reaction-time task

Chunk learning (the process by which a sequence is learned and retrieved from memory in smaller, decomposed units of information) has been postulated as the main learning mechanism underlying sequence learning (Perruchet & Pacton, 2006). However, the evidence for chunk formation has been elusive in the continuous serial reaction-time task, whereas other continuous, statistical processes of learning account well for the results observed in this task. This article proposes a new index to capture segmentation in learning, based on the variance of responding to different parts of a sequence. We assess the validity of this measure by comparing performance in a control group with that of another group in which color codes were used to induce a uniform segmentation. Results showed that evidence of chunking was obtained when the color codes were consistently coupled to responses, but that chunking was not maintained after the colors were removed.     

Why men (and women) do and don't rebel: effects of system justification on willingness to protest

Three studies examined the hypothesis that system justification is negatively associated with collective protest against ingroup disadvantage. Effects of uncertainty salience, ingroup identification, and disruptive versus nondisruptive protest were also investigated. In Study 1, college students who were exposed to an uncertainty salience manipulation and who scored higher on system justification were less likely to protest against the governmental bailout of Wall Street. In Study 2, May Day protesters in Greece who were primed with a system-justifying stereotype exhibited less group-based anger and willingness to protest. In Study 3, members of a British teachers union who were primed with a "system-rejecting" mind-set exhibited decreased system justification and increased willingness to protest. The effect of system justification on nondisruptive protest was mediated by group-based anger. Across very different contexts, measures, and methods, the results reveal that, even among political activists, system justification plays a significant role in undermining willingness to protest.     

Inferring the emotions of friends versus strangers: the role of culture and self-construal

Three studies examined cross-cultural differences in empathic accuracy (the ability to correctly infer another's emotional experience) within the context of different relationships. East-West cultural differences in self-construal were hypothesized to differentiate levels of empathic accuracy across relationship types. In contrast to the independent self prevalent among members of Western cultures, members of Eastern cultures generally view the self as interdependent with those with whom they have a relationship. Easterners, relative to Westerners, are more concerned with the thoughts or feelings of close others and less concerned with the thoughts or feelings of those with whom they have no relational link (i.e., strangers). Across three studies, the authors found that East Asians, compared with European Americans, made more accurate inferences regarding the emotions of close others (i.e., friends), but less accurate inferences regarding the emotions of strangers. Furthermore, individual differences in interdependent self-construal among East Asians predicted the degree of empathic accuracy.     

Knee muscle contributions to joint rotational stiffness

The purpose of this paper was to investigate total joint rotational stiffness (JRS) and relative muscle contributions to JRS with varying extensor moment demands. It was hypothesized that greater co-activation of the flexors at lower levels of moment would result in greater JRS, relative to moment demands. It was also hypothesized that the flexors would have greater relative JRS contributions at lower moment levels. Twelve male participants generated isometric extensor moments about the knee at varying intensities, during plateau and ramping (up and down) conditions. Electromyography was used to estimate individual muscle forces, which were used to calculate JRS about three orthogonal axes. Orthogonal trend analysis revealed a linear relationship (p<.001) between moment and JRS, about all axes. The vastus lateralis provided the greatest JRS about all axes. Of the flexors, the semimembranosis provided the most JRS about the flexion/extension (FE) and axial (AX) axes. However, while most muscle activity increased linearly, the gastrocnemious lateral (GL) had an interaction between condition and moment. Despite an extensor moment, the GL had minor contributions about the FE axis (1.2%), and it was postulated that this increase in activation was to stabilize about the VV axis, where its contribution was as high as 18.9%.