Do humans produce the speed–accuracy trade-off that maximizes reward rate?

In this paper we investigate trade-offs between speed and accuracy that are produced by humans when confronted with a sequence of choices between two alternatives. We assume that the choice process is described by the drift diffusion model, in which the speed–accuracy trade-off is primarily controlled by the value of the decision threshold. We test the hypothesis that participants choose the decision threshold that maximizes reward rate, defined as an average number of rewards per unit of time. In particular, we test four predictions derived on the basis of this hypothesis in two behavioural experiments. The data from all participants of our experiments provide support only for some of the predictions, and on average the participants are slower and more accurate than predicted by reward rate maximization. However, when we limit our analysis to subgroups of 30–50% of participants who earned the highest overall rewards, all the predictions are satisfied by the data. This suggests that a substantial subset of participants do select decision thresholds that maximize reward rate. We also discuss possible reasons why the remaining participants select thresholds higher than optimal, including the possibility that participants optimize a combination of reward rate and accuracy or that they compensate for the influence of timing uncertainty, or both.     

A response binding effect in visual short-term memory

The current study aimed to investigate the effect of action on the preservation of stored feature bindings. Prior research suggests that stimuli presented after a memory array can disrupt the feature bindings of memory array items. Here, we conducted three experiments to examine whether response to targets disrupts feature bindings. Two of four letters (A, B, C, D) were presented in a memory array, and were followed by a second array containing a single target letter. After either identifying or localizing the target letter, participants were required to report the identity or location of the memory array items. There was a deficit in memory performance involving spatial repetition when participants were required to localize targets, and involving identity repetition when participants were required to identify targets. We conclude that response codes are fundamentally linked to stimulus representations, and can affect retrieval from visual working memory.     

Imagining novel futures: The roles of event plausibility and familiarity

The constructive episodic simulation hypothesis suggests that episodic memory supports the simulation of future events through extraction and recombination of stored information. The current study explicitly investigated the use of past episodic thought in the simulation of future scenarios. Participants simulated one of three possible scenarios, differing in plausibility and participants’ prior experience of similar events. Participants recorded related memories and whether they were explicitly used during future event simulation. Memories were rated for source (self-experienced, other-experienced, or media). Findings suggest prior experience and event plausibility did not impact upon ease of future event simulation or the extent of memory usage during simulations. Differences emerged in the source of information used to assist future event simulation. These findings provide support for the hypothesis that episodic memories from a variety of sources are recombined when generating future simulations of novel events.     

急性心肌梗死患者直接经皮冠状动脉介入治疗前后窦性心律振荡的临床观察

探讨急性心肌梗死（AMI）患者直接经皮冠状动脉介入（PCI）前后窦性心律振荡（HRT）的变化及意义.选择伴室性早搏的AMI患者（观察组）和无器质性心脏病的室性早搏患者（对照组）各42例,PCI前伴室早的观察组患者,用节律Ⅱ导联记录室早的心电图,PCI后2周时观察组及对照组均记录24h动态心电图（AECG）,计算其震荡初始（TO）和震荡斜率（TS）,并行心脏彩色多普勒超声检查,测定左室射血分数（LVEF）.结果观察组PCI后2周时和对照组LVEF分别为：（59.1＆#177;7.5）%和（61.3＆#177;8.4）%.观察组PCI前TO显著升高,TS显著降低,差异有统计学意义（P＜0.05）;观察组PCI后2周TO较前降低,TS较前升高,但和对照组相比差异仍有统计学意义（P＜0.05）;观察组PCI后2周时和对照组左室射血分数（LVEF）相比无差异.提示AMI患者HRT减弱,PCI后2周HRT改善但和观察组相比仍有统计学意义,提示AMI患者PCI后早期仍存在心脏自主神经功能下降,HRT可作为评价AMI患者预后的一个指标.     

Benefits of belonging: Experimental manipulation of social inclusion to enhance psychological and physiological health parameters

Objective: Acute changes in social belonging are important triggers for alterations in health and well-being, yet research has emphasised the negative effects of ‘exclusion’ at the expense of evaluating the potentially positive effects of ‘inclusion’. This study examined the impact of acute belonging on physiological and psychological outcomes.

Design and main outcome measures: A healthy population (N?=?138) were randomly allocated to ‘included’ or ‘excluded’ conditions. Condition-dependent differences in pre/during-task heart rate and pre/post-task self-reports of negative/positive mood, and social self-esteem, were assessed.

Results: Included participants showed decreased heart rate and negative mood, and increased social self-esteem. No inclusion-related change in positive mood was shown. An increase in heart rate was observed in excluded participants though no changes in negative/positive mood or social self-esteem were shown. Shifts in social self-esteem acted as a mechanism through which inclusion/exclusion impacted upon negative and positive mood alterations. Results remained significant in presence of covariates (sex, global self-esteem, rumination and social anxiety).

Conclusion: Findings suggest that acting to enhance belonging through ‘inclusion’ resulted in adaptive physiological and psychological outcomes. Neutral and potentially protective responses were observed in the immediate aftermath of ‘exclusion’. Self-esteem served as one route through which these effects were transmitted.     

Book review

Abstract

Physical Activity & Behavioral Medicine. James f. Sallis Neville Owen Thousand Oaks, CA: Sage, 1999. 210 Pages. ISBN 0-8039-5996-6, cloth UK£33.00; ISBN 0-8039-5997-4, paper UK£15.99.     

The effect of tape-recorded relaxation training on well-being,symptoms, and peak expiratory flow rate in adult asthmatics: A pilot study

Abstract

Evidence indicates that psychological stress plays a role in precipitating and exacerbating asthma symptoms and suggests that relaxation techniques aimed at reducing stress and autonomic arousal leads to symptom reduction. This study explored the effect of a tape-recorded relaxation intervention on well-being (mood and stresson). asthma symptoms, and a measure of pulmonary function (PEFR). Twenty adult asthmatics were studied for 21 days in their natural environment using a multiple baseline design. Self-administered relaxation training (including both breathing exercises and muscle relaxation) led to decreased negative mood and stressor report. Reporting of asthma symptoms decreased over time, and PEFR was increased by relaxation training. Asthma medication use was unchanged. Results suggest that tape–recorded relaxation training positively impacts well-being, asthma symptoms. and PEFR in a naturalistic setting. Further study of the potential use of inexpensive tape-recorded interventions in chronic illness is warranted.     

On the ultra-high-strain rate shock deformation in copper single crystals: multiscale dislocation dynamics simulations

Multiscale dislocation dynamics plasticity (MDDP) calculations are carried out to simulate the mechanical response of copper single crystals that have undergone shock loading at high strain rates ranging from 1?×?10⁶ to 1?×?10¹⁰?s^?1. Plasticity mechanisms associated with both the activation of pre-existing dislocation sources and homogeneous nucleation of glide loops are considered. Our results show that there is a threshold strain rate of 10⁸?s^?1 at which the deformation mechanism changes from source activation to homogeneous nucleation. It is also illustrated that the pressure dependence on strain rate follows a one-fourth power law up to 10⁸?s^?1 beyond which the relationship assumes a one-half power law. The MDDP computations are in good agreement with recent experimental findings and compare well with the predictions of several dislocation-based continuum models.     

Prediction,events, and the advantage of Agents: The processing of semantic roles in visual narrative

Agents consistently appear prior to Patients in sentences, manual signs, and drawings, and Agents are responded to faster when presented in visual depictions of events. We hypothesized that this “Agent advantage” reflects Agents’ role in event structure. We investigated this question by manipulating the depictions of Agents and Patients in preparatory actions in wordless visual narratives. We found that Agents elicited a greater degree of predictions regarding upcoming events than Patients, that Agents are viewed longer than Patients, independent of serial order, and that visual depictions of actions are processed more quickly following the presentation of an Agent vs. a Patient. Taken together these findings support the notion that Agents initiate the building of event representation. We suggest that Agent First orders facilitate the interpretation of events as they unfold and that the saliency of Agents within visual representations of events is driven by anticipation of upcoming events.