Differential effects of voluntary expectancies on reaction times and event-related potentials: evidence for automatic and controlled expectancies.

Expectancy has been used to explain the effects of stimulus sequences both on reaction times (RTs) and on the P300 component of the human event-related potential. However, there are conflicting views about the control obtainable over these underlying expectancies. We compared the effects of voluntary expectancies for stimulus changes or repetitions in random tone series on RTs and the P300. Ss responded according to either stimulus identity (Experiment 1) or stimulus sequence (Experiment 2). In both experiments RTs were strongly affected by event expectedness. P300 amplitude, on the other hand, was affected (as a trend) only in Experiment 2. The results suggest that there are at least 2 types of "expectancy", one that is largely automatic and inflexible, reflected in P300 amplitude, and a second, controlled process that is reflected mainly in RT. The latter type of expectancy appears to affect processing stages beyond stimulus evaluation and classification.     

The effect of intentional expectancy on mental processing: a chronopsychophysiological investigation

Expected events are processed faster than unexpected ones. Previously, we have reported evidence that passive expectancies determined by the preceding event sequence mainly affected the duration of motoric processes. Here we examined the effects of instructed, intentional expectancies in a two-choice reaction time (RT) task. As predicted, RTs were shorter for expected than unexpected events. Onset of the lateralized readiness potential as an index of selective response activation, and the latency of the P300 component of the event-related potential, reflecting the duration of perceptual processing, indicated that intentional expectancy affected the time demands for central processing but did not influence the duration of early perceptual or motoric processes. Together the present and our previous results provide evidence that different kinds of expectancy can be distinguished by their locus of action within the information processing system.     

Expectancy and stimulus frequency: A comparative analysis in rats and humans

We examined whether expectancy, one of several factors influencing attention, is similarly affected in rats and humans by manipulation of relative stimulus frequency, A two-choice reaction time (RT) task was developed for rats, and an analogous task was used for humans. Errors, RTs, discriminability, and response bias were measured. Both rats and humans shifted their response bias to the more frequent stimulus, with no change in overall discriminability. As stimulus probability or stimulus repetition increased, RTs and errors decreased. These results illustrate the similarity of expectancy in rats and humans. This two-choice RT task for rats can be used in future studies to examine the neuronal mechanisms of expectancy and attention.     

奖赏预期对面孔情绪加工的影响：一项事件相关电位研究

采用事件相关电位(ERPs)技术考察了奖赏预期对人类面孔情绪识别的影响。实验采用线索-目标范式, 分别记录了被试在奖赏预期条件下以及无奖赏预期条件下对正性、中性和负性面孔进行情绪辨别任务的ERP数据。行为结果显示, 被试在奖赏预期条件下的反应时快于无奖赏预期条件下的反应时, 对情绪面孔的反应时快于对中性面孔的反应时。ERPs数据显示, 奖赏线索比无奖赏线索诱发了更正的P1、P2和P300成分。目标刺激诱发的P1、N170波幅以及N300均受到奖赏预期的调节, 在奖赏预期条件下目标诱发了更正的ERPs。P1、N170、VPP等成分没有受到面孔情绪的影响, 而额中央位置的N300波幅显示情绪(正性与负性)面孔与中性面孔加工的差异。重要的是, N300波幅出现奖赏预期与情绪的交互作用, 正、负情绪加工效应以及负性偏向效应受奖赏预期的差异性影响。正性情绪加工效应不受奖赏预期的影响, 而负性情绪加工效应和负性偏向效应在奖赏预期条件下显著大于无奖赏预期条件下。这些结果说明, 奖赏预期能够调节对面孔情绪的加工, 且不同加工进程中奖赏对情绪加工的调节作用不同。动机性信息调节注意资源的分配, 促进了个体在加工面孔情绪时的负性偏向。     

Expectancy and stimulus frequency: a comparative analysis in rats and humans.

We examined whether expectancy, one of several factors influencing attention, is similarly affected in rats and humans by manipulation of relative stimulus frequency. A two-choice reaction time (RT) task was developed for rats, and an analogous task was used for humans. Errors, RTs, discriminability, and response bias were measured. Both rats and humans shifted their response bias to the more frequent stimulus, with no change in overall discriminability. As stimulus probability or stimulus repetition increased, RTs and errors decreased. These results illustrate the similarity of expectancy in rats and humans. This two-choice RT task for rats can be used in future studies to examine the neuronal mechanisms of expectancy and attention.     

Anticipatory attention during the sleep onset period

To examine whether anticipatory attention or expectancy is a cognitive process that is automatic or requires conscious control, we employed a paired-stimulus event-related potential (ERP) paradigm during the transition to sleep. The slow negative ERP wave observed between two successive stimuli, the Contingent Negative Variation (CNV), reflects attention and expectancy to the second stimulus. Thirteen good sleepers were instructed to respond to the second stimulus in a pair during waking sessions. In a non-response paradigm modified for sleep, participants then fell asleep while tones played. As expected, N1 decreased and P2 increased in amplitude systematically with the loss of consciousness at sleep onset; the CNV was increasingly more positive. Sleep onset latency was correlated with the amplitude of the CNV. The systematic attenuation of the CNV waveform at sleep onset and its absence in sleep indicates that anticipatory attention requires endogenous conscious control.     

Affective recognition memory processing and event-related brain potentials

Recognition memory was examined for visual affective stimuli using behavioral and event-related brain potential (ERP) measures. Images from the International Affective Picture System (IAPS) that varied systematically in arousal level (low, high) and valence direction (unpleasant, pleasant) were first viewed passively. Then, during a response phase, the original images were intermixed with an equal number of new images and presented, and participants were instructed to press a button to indicate whether each stimulus picture was previously viewed (target) or new (foil). Participants were more sensitive to unpleasant- than to pleasant-valence stimuli and were biased to respond to high-arousal unpleasant stimuli as targets, whether the stimuli were previously viewed or new. Response times (RTs) to target stimuli were systematically affected by valence, whereas RTs to foil stimuli were influenced by arousal level. ERP component amplitudes were generally larger for high than for low arousal levels. The P300 (late positive component) amplitude was largest for high-arousal unpleasant target images. These and other amplitude effects suggest that high-arousal unpleasant stimuli engage a privileged memory-processing route during stimulus processing. Theoretical relationships between affective and memory processes are discussed.     

In the face of emotions: event-related potentials in supraliminal and subliminal facial expression recognition

Is facial expression recognition marked by specific event-related potentials (ERPs) effects? Are conscious and unconscious elaborations of emotional facial stimuli qualitatively different processes? In Experiment 1, ERPs elicited by supraliminal stimuli were recorded when 21 participants viewed emotional facial expressions of four emotions and a neutral stimulus. Two ERP components (N2 and P3) were analyzed for their peak amplitude and latency measures. First, emotional face-specificity was observed for the negative deflection N2, whereas P3 was not affected by the content of the stimulus (emotional or neutral). A more posterior distribution of ERPs was found for N2. Moreover, a lateralization effect was revealed for negative (right lateralization) and positive (left lateralization) facial expressions. In Experiment 2 (20 participants), 1-ms subliminal stimulation was carried out. Unaware information processing was revealed to be quite similar to aware information processing for peak amplitude but not for latency. In fact, unconscious stimulation produced a more delayed peak variation than conscious stimulation.     

Evaluating the relationship between explicit and implicit knowledge in a sequential reaction time task

Can knowledge underlying a simple perceptual-motor skill be unconscious? Three experiments (a) trained participants on a 4-choice reaction time (RT) task in which the stimulus on each trial was determined by a repeating 12-element sequence and (b) studied the extent to which participants' knowledge of this sequence was implicit, that is, unavailable for conscious access. Participants proved via an indirect test to have acquired knowledge of the sequence, because their RTs increased when the sequence was changed. To evaluate whether this knowledge was consciously accessible, participants were asked to perform an "objective" free-generation or recognition test of sequence knowledge. Results show that sequence knowledge is fully accessible on these objective tests. Moreover, it is demonstrated in this procedure that old-new recognition cannot be explained by unconscious attribution of perceptual-motor fluency. The question is raised whether distinct implicit (procedural) and explicit (declarative) forms of knowledge are acquired when participants learn a perceptual-motor skill.     

GKT范式在确定犯罪嫌疑人中的应用：一项ERP测谎研究

刑事犯罪已成为当今各国面临的普遍性社会问题,因此急需可靠有效的测谎技术以适应当前打击犯罪的严峻形势。本研究采用犯罪知识测试范式（Guilty knowledge test, GKT）,以犯罪嫌疑人为对象,以真实犯罪现场为素材,探究真实环境下与测谎探测相关的脑电指标（P300、CNV）的有效性和可靠性。行为数据显示,目标刺激的反应正确率显著小于探测和无关刺激,探测刺激的反应时显著小于目标刺激和无关刺激。脑电数据显示,相较于目标刺激和无关刺激,探测刺激诱发的P300波幅最大且P300的检出率为92.5%,而在CNV指标上目标刺激诱发的波幅最大, 无关刺激次之,探测刺激最小。结果表明,与CNV相比,P300能够有效检测被试所隐藏的犯罪细节信息,且检出率较高,稳定性较好,是一种较为可靠的测谎指标。     

Verbal predictions of unexpected stimuli and choice reaction time

In two choice reaction time (RT) experiments, subjects verbally predicted the stimulus alternative that was either most or least likely to be presented on each trial. An expectancy interpretation of prediction effects requires that stimuli matching least likely predictions yield the longest RTs. In Experiment 1, with four stimulus alternatives, RTs to stimuli matching the verbalized stimulus, both most likely and least likely predictions, were shorter than RTs to stimuli that matched neither the most nor the least likely predictions. However, matching most likely predictions produced faster responses with two alternatives. In Experiment 2, multiple predictions of both most and least likely stimuli were compared with joint predictions of first and second most likely alternatives. RTs to stimuli matching least likely predictions were longer than RTs to most likely matches, implicating prediction type as a partial determinant of RT. Matching least likely stimuli were responded to more quickly than unpredicted alternatives, demonstrating the importance of generating a prediction per se over the implied level of expectancy. Results from both experiments were contrasted with nonparametric predictions from an ordered memory scanning model.     

Combined expectancy effects: an accumulator model

When participants use cues to prepare for a likely stimulus or a likely response, reaction times are facilitated by valid cues but prolonged by invalid cues. In studies on combined expectancy effects, two cues give information regarding two dimensions of the forthcoming task. When the two cues consist of two separable stimuli their effects are approximately additive. When cues are presented as an integrated stimulus, cueing effects interact. A model is presented that simulates effects like these. The model assumes that cues affect different processing stages. When implicit information suggests that expectancies are unrelated, as for instance with separated cues, cueing effects at early and late levels of processing remain independent. When implicit information suggests that expectancies are related, as with integrated cues, however, a mechanism that is sensitive to the validity of the early stage cue, leads to an adjustment of the cueing effect at the late stage. The model is based on neurophysiologically plausible assumptions, it is given explicitly in mathematical terms, and it provides a good fit to a large body of empirical data.     

P300 stimulus sequence effects in children and adults

Immediate memory capability for 12 children (8 years) and 12 adults (21 years) was assessed electrophysiologically by using P300 event-related brain potential (ERP) stimulus sequences. These were derived from an auditory discrimination paradigm in which participants detected target stimuli in a series of target (T) and standard (S) tones that were varied by randomly presenting one of four sequence patterns (SSSS, TTTT, TTTS, SSST). Short-term memory capability was assessed behaviorally by recall performance of a 20-word list. Children and adults showed virtually identical P300 amplitude sequence patterns, such that for both groups component size increased systematically as the discrepancy between standard and target stimuli increased across sequence patterns. P300 latency evinced similar, albeit weaker, stimulus sequence effects, with children having longer component peak latencies. Memory recall performance was substantially weaker for the children than for adult participants, especially for recency effects. The findings suggest that immediate memory for stimulus sequences is fully developed in young children, although long-term memory is not.     

Inhibition of return for expected and unexpected targets

Inhibition of return (IOR) refers to slower reaction times (RTs) to targets that occur in the same, rather than in a different, location as a preceding onset cue. The present study examined IOR for expected (likely) and unexpected (unlikely) targets under conditions in which stimulus-response (S-R) expectancies were generated on a trial-by-trial basis or maintained across a block of trials. Three boxes were aligned along the vertical midline. In Experiments 1 and 2, the appearance of a cue in the upper or lower box was a signal to generate an expectancy about the most likely color of an impending discrimination target. In Experiment 3, one target color was more likely than another across a block of trials. In all cases, cue location did not predict target location. When S-R expectancies were generated on a trial-by-trial basis, IOR occurred for Unlikely targets but not for Likely targets; this was true across a range of cue-target stimulus onset asynchronies. In contrast, when S-R expectancies were maintained over a block of trials, IOR was larger for Likely than for Unlikely targets. These findings reveal a critical interaction of S-R expectancies with IOR. This interaction not only demonstrates the modulation of IOR by cognitive expectancies, but in doing so also provides evidence that is consistent with the view that IOR reflects a conservative response bias.     

无空间线索化下视觉注意空间等级的ERP研究

采用事件相关电位技术考察无空间线索化下视觉注意资源的在不同空间等级的分布情况。在“预警信号-目标探测”范式下,目标刺激随机出现在直径视角为3.2°、6.4°以及9.6°的三个空间等级圆上。反应时结果显示：随着注意空间直径视角增大,对目标刺激的探测速度逐渐下降。脑电结果显示：三种条件下目标刺激诱发的早期N1和晚期P3成分产生了不同程度分离,主要表现为两成分的波幅随着注意空间视角增大而减小。这说明个体在无空间线索化下自动地对不同空间等级进行有选择性的资源分配。     

Endogenous temporal orienting of attention in detection and discrimination tasks

Endogenous temporal-orienting effects were studied using a cuing paradigm in which the cue indicated the time interval during which the target was most likely to appear. Temporal-orienting effects were defined by lower reaction times (RTs) when there was a match between the temporal expectancy for a target (early or late) and the time interval during which the target actually appeared than when they mismatched. Temporal-orienting effects were found for both early and late expectancies with a detection task in Experiment 1. However, catch trials were decisive in whether temporal-orienting effects were observed in the early-expectancy condition. No temporal-orienting effects were found in the discrimination task. In Experiments 2A and 2B, temporal-orienting effects were observed in the discrimination task; however, they were larger when temporal expectancy was manipulated between blocks, rather than within blocks.     

Inductive parsimony and the Methodological Argument

Studies on so-called Change Blindness and Inattentional Blindness have been taken to establish the claim that conscious perception of a stimulus requires the attentional processing of that stimulus. One might contend, against this claim, that the evidence only shows attention to be necessary for the subject to have access to the contents of conscious perception and not for conscious perception itself. This "Methodological Argument" is gaining ground among philosophers who work on attention and consciousness, such as Christopher Mole. I find that, without the supporting evidence of inaccessible consciousness, this argument collapses into an indefensible form of inductive parsimony. The Methodological Argument is thus shown to be unsuccessful when used against the claim that attention is required for conscious perception, though I suggest that it may be successful against the more ambitious claim that attention is necessary for all conscious experience.     

The psychological refractory period and vertex evoked potentials

The averaged sensory evoked potential (EP) was recorded from the scalp (vertex to mastoid) in a psychological refractory period experiment in which 12 young adults participated. Reaction times (RTs) were measured to either both or only the second of pairs of stimuli, in different trial blocks, with inter-stimulus intervals (ISIs) of 100, 200, 300 and 400 msec occurring in random sequence. EPs were recorded at each ISI. No latency changes could be found in the prominent non-specific components (P1-N1-P2) of the EP to stimulus 2 even at ISIs where the RT was substantially delayed. Thus the notions that the RT2 delay is due to occupation of a single channel central processor by S1 and that non-specific EP components reflect the time course of information processing in underlying neural tissue, do not lend each other mutual support. Furthermore, as profound amplitude refractoriness in components P1-N1 and N1-P2 persisted at ISIs where RT was as fast or faster than simple RT, there appears to be a dissociation between “psychological refractoriness” and “physiological refractoriness”. The implications of these results are discussed.     

ERPs reveal similar effects of social gaze orienting and voluntary attention, and distinguish each from reflexive attention

Spatial attention can be reflexively captured by a physically salient stimulus, effortfully directed toward a relevant location, or involuntarily oriented in the direction of another person's gaze (i.e., social gaze orienting). Here, we used event-related potentials to compare the effects of these three types of orienting on multiple stages of subsequent target processing. Although gaze orienting has been associated more strongly with reflexive capture than with voluntary attention, the present data provide new evidence that the neural effects of social gaze orienting are markedly different from the effects of reflexive attentional capture by physically salient stimuli. Specifically, despite their similar behavioral effects, social gaze orienting and reflexive capture produce different effects on both early sensory processing (~120 ms; P1/N1 components) and later, higher-order processing (~300 ms; P3 component). In contrast, the effects of social gaze orienting were highly similar to those of voluntary orienting at these stages of target processing.     

What the experimenter’s prime tells the observer’s brain

The presentation of a stimulus below the threshold of conscious awareness can exert an influence on the processing of a subsequent target. One such consequence of briefly presented “primes” is seen in the negative compatibility effect. The response time (RT) to determine the left—right orientation of an arrow (i.e., the target) is relatively slow if a prime is also an arrow whose direction corresponds to that of the target. When the direction of the arrow is opposite that of the prime, RTs are relatively fast. In four experiments, we examined whether the prime shifts attention from the location of the subsequent target and whether this attention shift influences target processing. Results showed that the prime does indeed move attention. The consequence of this attention movement is that the representation of direction is affected. Specifically, RTs to process an arrow are shorter if the arrow’s direction is compatible with the last shift of attention. Furthermore, this interference occurs at a conceptual level concerning the representation of left and right rather than at the motor planning level. We argue that a shift in attention brought about by the prime can create a negative compatibility-like effect.