Influences of different combinations of conceptual, perceptual, and structural similarity on stimulus-response compatibility

This study evaluated the hypothesis that an increase in set-level stimulus-response compatibility produces facilitation for congruent mappings and interference for incongruent mappings. The degree of set-level compatibility was manipulated by varying combinations of conceptual, perceptual, and structural similarity. Experiment 1 varied perceptual similarity, by combining two stimulus codes (spatial, verbal) with two response modalities (manual, vocal) for orthogonal spatial dimensions, which have structural similarity. The element-level mapping effect did not vary as a function of the code-modality relation, in contrast to findings obtained with parallel spatial dimensions, which also have conceptual similarity. Experiment 2 manipulated combinations of conceptual and perceptual similarity by combining vertical and horizontal stimulus and response orientations, using verbal or spatial stimuli and vocal responses. The element-level mapping effect was larger for parallel than orthogonal orientations, with congruent mappings showing facilitation and incongruent mappings showing interference. The largest effect was facilitation for parallel orientations with the verbal-vocal set, consistent with the view that perceptual similarity contributes to performance primarily when responding with the identity of the stimulus. Our results indicate that conceptual similarity, but not perceptual similarity, produces the facilitation/interference pattern suggestive of automatic activation of the corresponding response regardless of mapping.     

Early evidence affects later decisions: Why evidence accumulation is required to explain response time data

Models of decision making differ in how they treat early evidence as it recedes in time. Standard models, such as the drift diffusion model, assume that evidence is gradually accumulated until it reaches a boundary and a decision is initiated. One recent model, the urgency gating model, has proposed that decision making does not require the accumulation of evidence at all. Instead, accumulation could be replaced by a simple urgency factor that scales with time. To distinguish between these fundamentally different accounts of decision making, we performed an experiment in which we manipulated the presence, duration, and valence of early evidence. We simulated the associated response time and error rate predictions from the drift diffusion model and the urgency gating model, fitting the models to the empirical data. The drift diffusion model predicted that variations in the evidence presented early in the trial would affect decisions later in that same trial. The urgency gating model predicted that none of these variations would have any effect. The behavioral data showed clear effects of early evidence on the subsequent decisions, in a manner consistent with the drift diffusion model. Our results cannot be explained by the urgency gating model, and they provide support for an evidence accumulation account of perceptual decision making.     

Motivation sharpens exogenous spatial attention

Although both attention and motivation affect behavior, how these 2 systems interact is currently unknown. To address this question, 2 experiments were conducted in which participants performed a spatially cued forced-choice localization task under varying levels of motivation. Participants were asked to indicate the location of a peripherally cued target while ignoring a distracter. Motivation was manipulated by varying magnitude and valence (reward and punishment) of an incentive linked to task performance. Attention was manipulated via a peripheral cue, which correctly predicted the presence of a target stimulus on 70% of the trials. Taken together, our findings revealed that the signal detection measure, reflecting perceptual sensitivity, increased as a function of incentive value during both valid and invalid trials. In addition, trend analyses revealed a linear increase in detection sensitivity as a function of incentive magnitude for both reward and punishment conditions. Our results suggest that elevated motivation leads to improved efficiency in orienting and reorienting of exogenous spatial attention and that one mechanism by which attention and motivation interact involves the sharpening of attention during motivationally salient conditions.     

Orthogonal stimulus–response compatibility effects emerge even when the stimulus position is task irrelevant

The above-right/below-left mapping advantage with vertical stimuli and horizontal responses is known as the orthogonal stimulus–response compatibility (SRC) effect. We investigated whether the orthogonal SRC effect emerges with irrelevant stimulus dimensions. In Experiment 1, participants responded with a right or left key press to the colour of the stimulus presented above or below the fixation. We observed an above-right/below-left advantage (orthogonal Simon effect). In Experiment 2, we manipulated the polarity in the response dimension by varying the horizontal location of the response set. The orthogonal Simon effect decreased and even reversed as the left response code became more positive. This result provides evidence for the automatic activation of the positive and negative response codes by the corresponding positive and negative stimulus codes. These findings extended the orthogonal SRC effect based on coding asymmetry to an irrelevant stimulus dimension.     

无意识信息的刺激表征及其时间特性

无意识信息是否存在刺激表征有待解决。实验采用字母Flanker任务, 通过目标和flanker在刺激水平和反应水平上的冲突效应, 重点考察阈下flanker在刺激水平的表征。在相同的实验设计下, flanker可觉察时(实验1A), 观察到经典的刺激冲突效应和反应冲突效应; 而flanker无意识时(实验1B), 重复了反应冲突效应, 却观察到刺激冲突效应发生反转, 提示了无意识信息的反应加工及刺激加工。实验2采用符号材料促使刺激−反应的自动联结, 减少刺激−反应规则的难度, 结果重复了实验1B的发现--无意识信息引起反转的刺激冲突。刺激冲突下反转效应的一致结果表明无意识信息的刺激表征影响了认知加工。实验3考察这种影响在时间进程上的特点。无意识刺激表征的影响随反应时变化：在快速反应中观察到刺激冲突效应, 之后该效应发生反转且反转量随反应时增加而增大。相反, 无意识反应表征的影响在不同反应时下保持稳定。以上结果提供了无意识信息存在刺激表征的行为学证据并揭示了其时间特性, 提供了无意识领域中不一致研究结果的整合思路。     

Categorization response time with multidimensional stimuli

Categorization response time (RT) was examined in three separate experiments, in each of which exemplars varied on two physical dimensions. Three different types of stimuli were used: (1) horizontal and vertical line segments of varying length that were joined at an upper left corner, (2) rectangles of varying width and height, and (3) circles or semicircles of varying size with a radial arm of varying orientation. No evidence was found that stimulus familiarity or the category prototypes played any special role in determining categorization RT. Instead, RT decreased with distance from the stimulus to the categorization decision bound.     

The speed and accuracy of perceptual decisions in a random-tone pitch task

Research in perceptual decision making is dominated by paradigms that tap the visual system, such as the random-dot motion (RDM) paradigm. In this study, we investigated whether the behavioral signature of perceptual decisions in the auditory domain is similar to those observed in the visual domain. We developed an auditory version of the RDM task, in which tones correspond to dots and pitch corresponds to motion (the random-tone pitch task, RTP). In this task, participants have to decide quickly whether the pitch of a “sound cloud” of tones is moving up or down. Stimulus strength and speed–accuracy trade-off were manipulated. To describe the relationship between stimulus strength and performance, we fitted the proportional-rate diffusion model to the data. The results showed a close coupling between stimulus strength and the speed and accuracy of perceptual decisions in both tasks. Additionally, we fitted the full drift diffusion model (DDM) to the data and showed that three of the four participants had similar speed–accuracy trade-offs in both tasks. However, for the RTP task, drift rates were larger and nondecision times slower, suggesting that some DDM parameters might be dependent on stimulus modality (drift rate and nondecision time), whereas others might not be (decision bound). The results illustrate that the RTP task is suitable for investigating the dynamics of auditory perceptual choices. Future studies using the task might help to investigate modality-specific effects on decision making at both the behavioral and neuronal levels.     

Hemispheric differences for feature perception

Summary Hemisphere differences for featural processing were investigated in three experiments. Stimulus arrays composed of the same background letter were presented tachistoscopically and the subject instructed to detect an embedded target letter. Background and target letter features were manipulated across studies, while stimulus arrays were presented at different retinal loci within experiments. Signal detection analysis revealed that left hemisphere stimulus presentations demonstrated slightly better detection when target and background features were relatively dissimilar, while right hemisphere stimulus presentations demonstrated better detection when target and background features were highly similar. Retinal locus generally decreased detection performance when the stimulus letters were dissimilar and interacted with hemispheric advantages. Both of these factors also were affected by changes in response criterion across experiments which were linked to target/background perceptual confusions. The findings suggest that the left and right hemispheres differ in their feature extraction capabilities during the early stages of visual stimulus processing.     

A new framework for modeling decisions about changing information: The Piecewise Linear Ballistic Accumulator model

In the real world, decision making processes must be able to integrate non-stationary information that changes systematically while the decision is in progress. Although theories of decision making have traditionally been applied to paradigms with stationary information, non-stationary stimuli are now of increasing theoretical interest. We use a random-dot motion paradigm along with cognitive modeling to investigate how the decision process is updated when a stimulus changes. Participants viewed a cloud of moving dots, where the motion switched directions midway through some trials, and were asked to determine the direction of motion. Behavioral results revealed a strong delay effect: after presentation of the initial motion direction there is a substantial time delay before the changed motion information is integrated into the decision process. To further investigate the underlying changes in the decision process, we developed a Piecewise Linear Ballistic Accumulator model (PLBA). The PLBA is efficient to simulate, enabling it to be fit to participant choice and response-time distribution data in a hierarchal modeling framework using a non-parametric approximate Bayesian algorithm. Consistent with behavioral results, PLBA fits confirmed the presence of a long delay between presentation and integration of new stimulus information, but did not support increased response caution in reaction to the change. We also found the decision process was not veridical, as symmetric stimulus change had an asymmetric effect on the rate of evidence accumulation. Thus, the perceptual decision process was slow to react to, and underestimated, new contrary motion information.     

Orthogonal stimulus-response compatibility effects emerge even when the stimulus position is task irrelevant

The above-right/below-left mapping advantage with vertical stimuli and horizontal responses is known as the orthogonal stimulus-response compatibility (SRC) effect. We investigated whether the orthogonal SRC effect emerges with irrelevant stimulus dimensions. In Experiment 1, participants responded with a right or left key press to the colour of the stimulus presented above or below the fixation. We observed an above-right/below-left advantage (orthogonal Simon effect). In Experiment 2, we manipulated the polarity in the response dimension by varying the horizontal location of the response set. The orthogonal Simon effect decreased and even reversed as the left response code became more positive. This result provides evidence for the automatic activation of the positive and negative response codes by the corresponding positive and negative stimulus codes. These findings extended the orthogonal SRC effect based on coding asymmetry to an irrelevant stimulus dimension.     

Slow and steady? Strategic adjustments in response caution are moderately reliable and correlate across tasks

Speed-accuracy trade-offs are often considered a confound in speeded choice tasks, but individual differences in strategy have been linked to personality and brain structure. We ask whether strategic adjustments in response caution are reliable, and whether they correlate across tasks and with impulsivity traits. In Study 1, participants performed Eriksen flanker and Stroop tasks in two sessions four weeks apart. We manipulated response caution by emphasising speed or accuracy. We fit the diffusion model for conflict tasks and correlated the change in boundary (accuracy – speed) across session and task. We observed moderate test-retest reliability, and medium to large correlations across tasks. We replicated this between-task correlation in Study 2 using flanker and perceptual decision tasks. We found no consistent correlations with impulsivity. Though moderate reliability poses a challenge for researchers interested in stable traits, consistent correlation between tasks indicates there are meaningful individual differences in the speed-accuracy trade-off.     

The optimal experimental design for multiple alternatives perceptual search

Perceptual bias is inherent to all our senses, particularly in the form of visual illusions and aftereffects. However, many experiments measuring perceptual biases may be susceptible to nonperceptual factors, such as response bias and decision criteria. Here, we quantify how robust multiple alternative perceptual search (MAPS) is for disentangling estimates of perceptual biases from these confounding factors. First, our results show that while there are considerable response biases in our four-alternative forced-choice design, these are unrelated to perceptual biases estimates, and these response biases are not produced by the response modality (keyboard vs. mouse). We also show that perceptual bias estimates are reduced when feedback is given on each trial, likely due to feedback enabling observers to partially (and actively) correct for perceptual biases. However, this does not impact the reliability with which MAPS detects the presence of perceptual biases. Finally, our results show that MAPS can detect actual perceptual biases and is not a decisional bias towards choosing the target in the middle of the candidate stimulus distribution. In summary, researchers conducting a MAPS experiment should use a constant reference stimulus, but consider varying the mean of the candidate distribution. Ideally, they should not employ trial-wise feedback if the magnitude of perceptual biases is of interest.     

Variance misperception explains illusions of confidence in simple perceptual decisions

Confidence in a perceptual decision is a judgment about the quality of the sensory evidence. The quality of the evidence depends not only on its strength (‘signal’) but critically on its reliability (‘noise’), but the separate contribution of these quantities to the formation of confidence judgments has not been investigated before in the context of perceptual decisions. We studied subjective confidence reports in a multi-element perceptual task where evidence strength and reliability could be manipulated independently. Our results reveal a confidence paradox: confidence is higher for stimuli of lower reliability that are associated with a lower accuracy. We show that the subjects’ overconfidence in trials with unreliable evidence is caused by a reduced sensitivity to stimulus variability. Our results bridge between the investigation of miss-attributions of confidence in behavioral economics and the domain of simple perceptual decisions amenable to neuroscience research.     

The hierarchy of task decision and response selection: A task-switching event related potentials study

According to “hierarchical” multi-step theories, response selection is preceded by a decision regarding which task rule should be executed. Other theories assume a “flat” single-step architecture in which task information and stimulus information are simultaneously considered. Using task switching, the authors independently manipulated two kinds of conflict: task conflict (with information that potentially triggers the relevant or the competing task rule/identity) and response conflict (with information that potentially triggers the relevant or the competing response code/motor response). Event related potentials indicated that the task conflict effect began before the response conflict effect and carried on in parallel with it. These results are more in line with the hierarchical view.     

知觉冲突信息对他人印象控制策略的影响:以直接信息与间接信息为例

个体根据知觉选择、反应偏向以及实时更新的情境信息调节自身状态,以适应性地促进对当前知觉信息的灵活编码,这一过程即为印象形成的认知控制。采用词语判断任务操控直接信息与间接信息,通过侧抑制任务的变式对知觉对象进行高、低负载两种水平的加工,考察了不同类型的冲突信息及其知觉负载对他人印象控制策略的影响。结果发现:知觉负载对印象控制策略的调节作用会依据知觉信息的类型(冲突vs.相容)而变化。具体而言,当知觉信息相容时,个体的印象控制策略仅受知觉负载的调节而产生效应,即高知觉负载的个体易采取主动性控制策略而进行自上而下的线索驱动性加工,低知觉负载的个体则易采取反应性控制策略而进行自下而上的探测驱动性加工; 当知觉信息冲突时,个体的知觉负载效应消失,即对冲突信息的印象控制策略受到知觉信息的类型(冲突vs.相容)与知觉负载双重调节:高知觉负载的个体易采取反应性控制策略而激活反刻板印象,从而在印象加工中出现冲突适应偏向; 低知觉负载的个体则易采取主动性控制策略而激活刻板印象,从而在印象加工中出现冲突抑制偏向。这些结果表明,仅当他人信息不存在冲突时,知觉负载对印象控制策略的调节才发挥单一效应。     

High working memory load leads to more Ebbinghaus illusion

The evidence that distractor processing increases with greater load on working memory has come mainly from Stroop-type interference tasks, making it difficult to establish whether cognitive load affects distractor processing at the perceptual level or during response selection. We measured the Ebbinghaus illusion under varying levels of working memory load to test whether cognitive control is also relevant for preventing processing of distractors that do not produce any response conflict, and instead affect target processing at the perceptual level. The Ebbinghaus illusion was greater under high working memory load, suggesting that availability of cognitive control functions is critical to reduce distractor processing even for distractors that are not associated with a response. We conclude that the effect of loading working memory during selective attention leads to greater distractor perception.     

Comparison of perceptual and motor latencies via anticipatory and reactive response times

To compare the timing of perceptual and motor decisions, distinct tasks have been designed, all of which have yielded systematic differences between these two moments. These observations have been taken as evidence of a sensorimotor dissociation. Inasmuch as the distinction between perceptual and motor decision moments is conceptually warranted, this conclusion remains debatable, since the observed differences may reflect the dissimilarity between the stimulations/tasks used to assess them. Here, we minimize such dissimilarities by comparing response time (RT) and anticipatory RT (ART), an alternative technique with which to infer the relative perceptual decision moments. Observers pressed a key either in synchrony with the third of a sequence of three stimuli appearing at a constant pace (ART) or in response to the onset of this third stimulus presented at a random interval after the second (RT). Hence, the two stimulation sequences were virtually identical. Both the mean and the variance of RT were affected by stimulus intensity about 1.5 times more than were the mean and the variance of ART. Within the framework of two simple integration-to-bound models, these findings are compatible with the hypothesis that perceptual and motor decisions operate on the same internal signal but are based on distinct criteria, with the perceptual criterion lower than the motor one.     

Attention to local form information can prevent access to semantic information.

Humphreys and Boucart (1997) have shown that when processing of local form is required for response, surrounding global information is automatically processed to a semantic level. The generality of this effect was investigated in two experiments in which the perceptual load of the relevant local form information was manipulated, as was uncertainty about perceptual load. Participants attended to a single line segment inside a picture of an animal or a vehicle and then decided which of two pictures in the target/distractor display that followed contained a line segment that matched the first in orientation. The perceptual load of the relevant local form information was either low (the matching line segment was one of the solitary line segments presented in the centre ofthe target and distractor pictures), or high (the matching line segment was part of one of the solitary letters presented in the centre of the target and distractor pictures). The semantic relations among the pictures were manipulated, and when perceptual load remained constant across trials, semantic relations affected performance in the low-load but not in the high-load condition. When perceptual load varied from trial to trial, there was no evidence of any semantic processing on either low- or high-load trials. The results suggest that in form-matching tasks, attentional priority can be given to local information, thus preventing access to semantic information derived from global shape. They further suggest that the distribution of attention is not dictated entirely by the actual perceptual demands of the relevant stimulus, indicating an important role for top-down processing.     

Consonant recognition with two levels of decision complexity

The perceptual tuning hypothesis can be expressed as a prediction that discrimination of a particular stimulus dimension will be enhanced if it is the only dimension requiring discrimination and not one of a set of dimensions in a multidimensional discrimination task. In previous tests of the tuning hypothesis, using speech material, the size of a message set has been manipulated as an indirect means of controlling the number of dimensions an observer is required to discriminate. In the present experiments the particular items appearing in a message set have been selected in order to control precisely the number of dimensions relevant to the discrimination task, and performance is estimated in terms of the discrimination of each relevant dimension. No evidence is found for a perceptual tuning effect even though it is argued that the conditions of the present experiment represent those most favourable for its elicitation.     

On the relation between decision rules and perceptual representation in multidimensional perceptual categorization

This article examines the relation between changing categorization decision rules and the nature of the underlying perceptual representation. Observers completed a matching task that required them to adjust the length and orientation of a single line stimulus until they perceived it to "match" a second line stimulus (Alfonso-Reese, 1996, 1997). The same observers then completed four categorization tasks with the same stimuli. Data from the matching task were used to estimate a perceptual representation for each stimulus and observer. Three hypotheses regarding potential interactions between categorization decision rules and perceptual representation were examined. One assumed that there was no interaction between decision rules and perceptual representation. The second assumed that linear categorization rules affect the perceptual representation differently from nonlinear categorization rules. The third assumed that dimensional integration rules affected the perceptual representation differently from decision rules that require the observer to set a criterion along one stimulus dimension while ignoring the other; this is referred to as decisional selective attention. The results suggested that (1) the matching task perceptual representation provided a good account of the categorization data, (2) decisional selective attention affected the perceptual representation differently from decisional integration, and (3) decisional selective attention generally decreased the perceptual variability along the attended dimension.