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.     

Representation,Presentation and the Epistemic Role of Perceptual Experience

Abstract

In this paper I argue that the representational theory of perception, on which the world is represented as being a certain way in perceptual experience, cannot explain how there can be a genuinely epistemic connection between experience and belief. I try to show that we are positively required to deny that perceptual consciousness is contentful if we want to make its fitness for epistemic duties intelligible. (So versions of the representational theory on which experience has a merely causal purchase on belief are not considered.) But my aim is not just negative. I try to defeat representationalism in such a way as to motivate a robustly presentational theory of perception. According to such a theory, perceptions are relations not between a subject and a content but between a subject and an ordinary object (such that if the relation holds at t, an appropriate subject and object must exist at t, and the object must be presented to the subject). I end by sketching an account of perceptual experience that is meant to show that, contrary to a very popular misconception, there is a way to conceive perceptual consciousness as relational and presentational (not intentional and representational) that does not succumb to the celebrated ‘myth of the Given’.     

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.     

Response-dependent point loss and response force as disrupting operations on behavioral resistance to change in humans

Behavioral momentum theory (BMT) provides a theoretical and methodological framework for understanding how differentially maintained operant responding resists disruption. A common way to test operant resistance involves contingencies with suppressive effects, such as extinction or prefeeding. Other contingencies with known suppressive effects, such as response-cost procedures arranged as point-loss or increases in response force, remain untested as disruptive events within the BMT framework. In the present set of three experiments, responding of humans was maintained by point accumulation programmed according to a multiple variable-interval (VI) VI schedule with different reinforcement rates in either of two components. Subsequently, subtracting a point following each response (Experiment 1) or increasing the force required for the response to be registered (Experiments 2 and 3 decreased response rates, but responding was less disrupted in the component associated with the higher reinforcement rate. The point-loss contingency and increased response force similarly affected response rates by suppressing responding and human persistence, replicating previous findings with humans and nonhuman animals when other types of disruptive events (e.g., extinction and prefeeding) were investigated. The present findings moreover extend the generality of the effects of reinforcement rate on persistence, and thus BMT, extending the analysis of resistance to two well-known manipulations used to reduce responding in the experimental analysis of behavior.     

The effects of presentation rate and retention interval on memory for items and associations in younger adults: A simulation of older adults’ associative memory deficit

Older adults show an associative deficit in episodic memory compared to younger adults. Previous research suggests both strategic and automatic binding deficits contribute to older adults’ poorer memory performance. Using behavioral manipulations designed to affect strategic and automatic binding of associations, three experiments attempted to simulate an associative deficit in younger adults. In these experiments participants learned face-scene pairs and then were given item and associative recognition memory tests. We manipulated the time allotted at encoding and retrieval to simulate strategic deficits, and the length of the retention interval to simulate automatic deficits. Results indicate that both manipulations separately contribute to a differential decline in associative memory, similar to the one shown by older adults, especially as reflected in the differential increase in false alarm rate in the associative memory test more than in the item memory test. Considerations of possible underlying brain mechanisms are discussed.