Coordinating cognition: the costs and benefits of shared gaze during collaborative search

Collaboration has its benefits, but coordination has its costs. We explored the potential for remotely located pairs of people to collaborate during visual search, using shared gaze and speech. Pairs of searchers wearing eyetrackers jointly performed an O-in-Qs search task alone, or in one of three collaboration conditions: shared gaze (with one searcher seeing a gaze-cursor indicating where the other was looking, and vice versa), shared-voice (by speaking to each other), and shared-gaze-plus-voice (by using both gaze-cursors and speech). Although collaborating pairs performed better than solitary searchers, search in the shared gaze condition was best of all: twice as fast and efficient as solitary search. People can successfully communicate and coordinate their searching labor using shared gaze alone. Strikingly, shared gaze search was even faster than shared-gaze-plus-voice search; speaking incurred substantial coordination costs. We conclude that shared gaze affords a highly efficient method of coordinating parallel activity in a time-critical spatial task.     

Role of endpoints and closures in feature search1

Abstract: The present study intended to examine the role of endpoints and of closures, the two most frequently referred to features, in a feature‐search paradigm. Two experiments were conducted with a rigorous stimulus control using random lined figures of different levels of complexity. The experiments gave almost identical results: there was no search asymmetry between the two features, smaller latencies were obtained in the presence of a feature as a target rather than in its absence, and the latencies were smaller for the displays having a background consisting of closures rather than for those having a background of endpoints. The results were more comprehensively explained by the high contrast between an endpoint as a target and closures as a background, rather than the conspicuity of an endpoint as a target. The possibility for closures to group into a homogeneous ground was discussed.     

Frames of reference for the light-from-above prior in visual search and shape judgements

Faced with highly complex and ambiguous visual input, human observers must rely on prior knowledge and assumptions to efficiently determine the structure of their surroundings. One of these assumptions is the 'light-from-above' prior. In the absence of explicit light-source information, the visual system assumes that the light-source is roughly overhead. A simple, low-cost strategy would place this 'light-from-above' prior in a retinal frame of reference. A more complex, but optimal strategy would be to assume that the light-source is gravitationally up, and compensate for observer orientation. Evidence to support one or other strategy from psychophysics and neurophysiology has been mixed. This paper pits the gravitational and retinal frames against each other in two different visual tasks that relate to the light-from-above prior. In the first task, observers had to report the presence or absence of a target where distractors and target were defined purely by shading. In the second task, observers made explicit shape judgements of similar stimuli. The orientation of the stimuli varied across trials and the observer's head was fixed at 0, +/-45 or +/-60 degrees . In both tasks the retinal frame of reference dominated. Visual search behaviour with shape-from-shading stimuli (SFS) was modulated purely by stimulus orientation relative to the retina. However, the gravitational frame of reference had a significant effect on shape judgements, with a 30% correction for observer orientation. In other words, shading information is processed quite differently depending on the demands of the current task. When a 'quick and dirty' representation is required to drive fast, efficient search, that is what the visual system provides. In contrast, when the task is to explicitly estimate shape, extra processing to compensate for head orientation precedes the perceptual judgment. These results are consistent with current neurophysiological data on SFS if we re-frame compensation for observer orientation as a cue-combination problem.     

Faceted Thesauri

The basic elements of faceted thesauri are described, together with a review of their origins and some prominent examples. Their use in browsing and searching applications is discussed. Faceted thesauri are distinguished from faceted classification schemes, while acknowledging the close similarities. The paper concludes by comparing faceted thesauri and related knowledge organization systems to ontologies and discussing appropriate areas of use.     

A new secretary problem with rank-based selection and cardinal payoffs

We present an extension of the secretary problem in which the decision maker (DM) sequentially observes up to n applicants whose values are random variables X₁,X₂,…,X_n drawn i.i.d. from a uniform distribution on [0,1]. The DM must select exactly one applicant, cannot recall released applicants, and receives a payoff of x_t, the realization of X_t, for selecting the tth applicant. For each encountered applicant, the DM only learns whether the applicant is the best so far. We prove that the optimal policy dictates skipping the first sqrt(n)-1 applicants, and then selecting the next encountered applicant whose value is a maximum.     

The effects of task-irrelevant threatening stimuli on orienting- and executive attentional processes under cognitive load

Human visual attention is biased to rapidly detect threats in the environment so that our nervous system can initiate quick reactions. The processes underlying threat detection (and how they operate under cognitive load), however, are still poorly understood. Thus, we sought to test the impact of task-irrelevant threatening stimuli on the salience network and executive control of attention during low and high cognitive load. Participants were exposed to neutral or threatening pictures (with moderate and high arousal levels) as task-irrelevant distractors in near (parafoveal) and far (peripheral) positions while searching for numbers in ascending order in a matrix array. We measured reaction times and recorded eye-movements. Our results showed that task-irrelevant distractors primarily influenced behavioural measures during high cognitive load. The distracting effect of threatening images with moderate arousal level slowed reaction times for finding the first number. However, this slowing was offset by high arousal threatening stimuli, leading to overall shorter search times. Eye-tracking measures showed that participants fixated threatening pictures more later and for shorter durations compared to neutral images. Together, our results indicate a complex relationship between threats and attention that results not in a unitary bias but in a sequence of effects that unfold over time.     

预览搜索中基于颜色的两种自上而下加工

预览搜索（preview search）研究是近几年来注意选择研究领域新的热点。本研究将预览搜索任务和探测任务相结合,通过两个实验证明了预览搜索中存在基于颜色的自上而下加工。在每次实验中,先出现预览项目,然后让被试根据有无提示音完成搜索任务或探测任务。在实验一中,探测点的颜色为旧项目同色和无关色两种;在实验二中,探测点的颜色为新项目同色和无关色两种。结果发现,旧项目同色的探测子的反应时长于无关色反应时,而新项目同色的探测子的反应时短于无关色反应时。笔者认为这是由于在预览阶段,可能存在两种自上而下加工,一种是主要基于旧项目颜色的抑制定势,另一种是基于靶子颜色的预期定势。这两种自上而下的调控机制可以解释预览效应的原因,同时利用颜色等特征的格式塔组织也在预览搜索中起着重要的作用     

Antecedents and consequences of the frequency of upward and downward social comparisons at work

The current paper examines the dispositional and situational antecedents, as well as the attitudinal and behavioral consequences, of the frequency of upward and downward social comparisons. We predicted social comparison frequency would be influenced by uncertainty-related antecedents, and that social comparisons in organizations would be characterized by contrast, not assimilation, effects. A large and occupationally diverse sample of 991 employed adults was surveyed at three separate points in time over a 12–16 week period. Our results, based on structural equation modeling, indicated that (a) role ambiguity, task autonomy, and core self-evaluations were significant predictors of upward social comparison, (b) upward social comparison was significantly negatively related to job satisfaction and affective commitment, (c) downward social comparison was significantly positively related to job satisfaction and affective commitment, and (d) upward and downward social comparisons had significant positive and negative indirect effects on the frequency of job search behaviors, respectively. The findings are discussed in terms of their general implications for understanding the importance of directional social comparison processes in organizational settings.     

A model of working memory capacity in the radial-arm maze task

The radial arm maze is one of the most commonly used tests for assessing working memory in laboratory animals. However, to date, there exists no quantitative method of estimating working memory capacity from performance on this task. Here, we present a mathematical model of performance on the radial arm maze from which we can derive estimates of capacity. We derive explicit results for the two most commonly used measures of performance as functions of number of arms in the maze and memory capacity, assuming a uniform random search. We simulate random non-uniform search strategies. Comparing our model to previous experiments, we show that our model predicts a working memory capacity in the range of 3-9 at the level of performance observed in these experiments. This estimate is within the typical estimate of human working memory capacity. Performance of rats on large mazes (e.g. 48 arms) has been used as evidence that the working memory capacity of rats may be significantly larger than that of humans. We report that memory capacity in the range 3-9 is sufficient to explain the performance of rats in very large radial mazes. Furthermore, when we simulate non-uniform random search strategies observed in the experiments, the resulting estimates do not differ significantly from those assuming a uniform random search. We conclude that a list-based model of working memory with modest capacity is more powerful than previously expected.     

预搜索过滤分心物的机制

如果先呈现若干分心物,然后添加靶子与其他分心物,那么就会改善搜索——预搜索效应。对于过滤分心物的潜在机制,研究者相继提出了主动抑制说、突然呈现说与时间分离说等理论。这些理论都有其合理的一面,能解释一些特定的实验现象,但任何单一机制都无法解释所有的实验现象。文章提出,未来的研究应该整合已有的实验现象与理论,系统考察旧客体与新客体的作用,重点整合抑制说与突现说,它们可能是一个连续体的两端