知觉组织对时序知觉的双重影响:同时判断任务的证据

本研究探讨知觉组织对时序知觉的双重影响。实验采用三条线段构成的C形为实验材料,操纵图形朝向和SOA水平(实验1和实验2)、图形颜色(实验3)以及反应限制(实验4),要求被试完成同时判断任务。结果发现,在不同的SOA条件下,图形对向条件的同时判断频率均显著高于图形反向条件(实验1),即使在知觉组织线索弱化时这种现象仍然存在(实验2和实验3),而且知觉组织对时序知觉的影响不是由于被试的反应偏向导致的(实验4)。结果说明知觉组织对时序知觉存在双重影响:当两个刺激同时出现时,知觉组织能够提高时序知觉表现; 而当两个刺激非同时出现时,知觉组织显著降低时序知觉表现。     

判断框架对时序知觉位置启动效应的影响

研究采用包含两种判断框架（判断刺激出现的先后次序）的时序判断任务探讨了决策偏向对时序知觉位置启动效应的影响。实验结果表明,时序知觉中存在着位置启动效应,而且在两个靶刺激出现时间间隔不同时,被试在“哪个靶刺激先出现”和“哪个靶刺激后出现”两种判断框架下的正确率存在显著差异,但在两个靶刺激同时出现时并没有出现显著的判断框架效应。因此,本研究推测时序知觉位置启动效应的作用机制不仅包括知觉增强加工过程,而且也与认知决策有关,这为反应偏向理论提供了新的支持证据。     

反应选项对时序知觉重复启动效应的影响

先前研究采用两项反应任务发现了时序知觉重复启动效应, 这可能是反应选项导致的虚假效应, 本研究采用三项反应任务对此进行了检验。实验1运用三项判断任务以消除缺乏中间选项所致的反应偏向, 结果发现重复启动显著影响“哪个图形先出现”和“两个图形同时出现”的时序判断; 实验2在实验1的基础上对“同时出现”反应选项进行两种指导语操作, 实验结果不仅与实验1一致, 而且“有把握时判断为同时出现”和“有无把握都判断为同时出现”之间没有显著差异, 说明被试能够识别时序加以判断, 不支持反应偏向的前提条件。因此, 时序知觉重复启动效应不是反应选项产生的反应偏向引发的虚假效应, 重复启动对“系列性”和“同时性”时序知觉都存在显著影响。     

关于知觉干扰效应的ERP研究

利用ERP技术,采用知觉干扰效应的经典实验范式,首次从神经生理水平上探究知觉干扰效应的内部机制。结果发现,递进条件和标准条件均诱发了P2,P3,N400和晚期正成分LPC。在P2,P3和LPC成分上,标准条件的波幅均显著大于递进条件;在N400成分上,递进条件比标准条件波幅更负,潜伏期更长。此外,对递进条件下靶字各模糊水平（Level 1～Level 5）的ERPs进行比较分析表明,N400成分的波幅在各模糊水平间的差异均不显著。基本支持失匹配理论及词汇自动加工理论。     

重复启动对时序知觉的影响

在时序判断任务中,重复启动导致被试把启动的靶刺激知觉为先出现的。知觉加工增强观和决策反应偏向观都试图解释其机制,但仍存在争议。本研究采用图形材料,通过三个实验系统考察了重复启动对时序知觉的影响。实验结果显示,启动和指导语都具有显著效应。这说明,重复启动对时序知觉的影响涉及知觉加工和决策水平两个方面。实验还首次发现,在启动的靶刺激先出现时发生了重复启动效应的反转。最后,研究提出了双加工表征匹配调节假说,用以综合解释目前的研究结果     

视觉工作记忆参与融景知觉

融景知觉现象是指观察者任意时刻虽然只能观察到部分刺激模式,却能基于部分刺激模式形成完整知觉。完成融景知觉的关键在于需要将时间序列上的信息进行整合。根据视知觉与视觉工作记忆动态交互模型,完成信息整合需视觉工作记忆的参与。然而以往研究均关注融景现象的知觉加工特性,尚未涉及视觉工作记忆在该现象中的作用机制。笔者采用双任务范式,要求被试完成规则或不规则刺激模式的融景知觉,同时操纵工作记忆负荷,以考察记忆负荷对融景知觉的影响。结果发现,高记忆负荷显著降低不规则刺激的融景知觉绩效(实验一);且该效应并非由记忆负荷对融景刺激维持阶段的影响所致(实验二)。上述结果说明,至少对不规则图形的融景知觉需要视觉工作记忆参与。     

重复启动对时序知觉和时距知觉的影响

采用时序判断和时距估计任务,探讨重复启动对时序知觉和时距知觉的影响。结果表明：在时序判断中,当未启动的靶刺激先出现时出现了显著的启动效应,启动的靶刺激被知觉为早出现;在启动的靶刺激先出现时产生了启动效应的反转,启动的靶刺激被知觉为后出现。在时距估计中,启动条件下的两个靶刺激之间的时距长度被知觉为显著长于未启动条件下的时距长度。因此,在同一时间历程中,重复启动对时序知觉和时距估计都存在显著影响,启动刺激所引发的表征激活和反应抑制双加工过程在时序知觉中是按照表征匹配机制、在时距知觉中是基于唤醒机制起作用,这为时间认知分段综合模型的理论构想提供了支持证据。     

时序知觉研究方法及其影响因素

时序知觉是个体对直接作用于感觉器官的客观事件顺序性的知觉。时序判断任务和同时性判断任务是研究时序知觉的经典实验范式。时序知觉不仅受机体变量,刺激变量及反应变量的影响,还受注意和通道等中介变量的影响。个体的意识和潜意识在同时性、非同时性和序列性时间知觉中的作用问题有待进一步探索。     

聋生1秒以下与以上的视时距知觉研究

采用时距二分任务,探讨聋生在视觉通道的1s以下和1s以上时距知觉的特点。结果发现,在1s以下条件下,聋生时距判断准确性低于普通学生;聋生CNV峰值与LPCt波幅低于普通学生,CNV潜伏期短于普通学生,LPCt峰值潜伏期长于普通学生。在1s以上条件下,聋生时距判断准确性高于普通学生;聋生N1、P2、CNV与LPCt成分各项指标与普通学生均没有显著差异。这说明,听觉丧失损伤了聋生1s以下的时距记忆与决策过程,支持了普遍缺陷假设;但听觉丧失未对聋生1s以上时距加工产生显著影响,支持了感觉补偿机制。因此,时距长度在听觉丧失对视觉时距知觉的影响中具有调节作用,为时间认知的分段综合模型提供了新的支持证据。     

语言范畴影响面部表情知觉的电生理学证据

本研究探讨了语言范畴影响面部表情知觉的时程及大脑偏侧化特点。采用从快乐到恐惧渐变的4张人类面孔表情图片为实验材料，以分视野呈现刺激的oddball范式设计脑电实验，并以分心任务使被试不注意实验表情图片之间的差异。实验结果显示，表情知觉诱发的ERP成分N1和N2上均出现了偏右视野-左脑表情范畴知觉，即在右视野呈现的条件下，范畴间偏差刺激比范畴内偏差刺激诱发了更大的vMMN效应，而在左视野呈现的条件下，两类偏差刺激诱发的vMMN效应无显著差异。这一结果表明表情范畴知觉发生在表情知觉的早期感觉水平加工及后知觉加工阶段，且具有偏右视野-左脑特性，提示语言范畴会同时影响早期、注意前表情知觉及后知觉加工，支持了沃尔夫假说。     

Developmental versus sensory deficit effects on perceptual processing in the reading disabled

Thirty children and 5 adults participated in two experiments designed to compare visual processing in normal and reading disabled children. The children were aged 8, 10, and 12 years. In Experiment 1, subjects were asked to detect the temporal order of two briefly presented stimuli. In Experiment 2, subjects sorted cards containing bracket stimuli that did or did not produce perceptual grouping effects. Poor readers required more time to make accurate temporal order judgments and showed stronger perceptual grouping effects. For both good and poor readers, the amount of time necessary to make a correct temporal order judgment decreased, and perceptual grouping effects became weaker with age. However, the magnitude of the difference between the groups did not lessen with age. These results suggest that there are visual processing differences between good and poor readers that do not appear to correct by age 12.     

Visual training improves perceptual grouping based on basic stimulus features

Training on visual tasks improves performance on basic and higher order visual capacities. Such improvement has been linked to changes in connectivity among mediating neurons. We investigated whether training effects occur for perceptual grouping. It was hypothesized that repeated engagement of integration mechanisms would enhance grouping processes. Thirty-six participants underwent 15 sessions of training on a visual discrimination task that required perceptual grouping. Participants viewed 20?×?20 arrays of dots or Gabor patches and indicated whether the array appeared grouped as vertical or horizontal lines. Across trials stimuli became progressively disorganized, contingent upon successful discrimination. Four visual dimensions were examined, in which grouping was based on similarity in luminance, color, orientation, and motion. Psychophysical thresholds of grouping were assessed before and after training. Results indicate that performance in all four dimensions improved with training. Training on a control condition, which paralleled the discrimination task but without a grouping component, produced no improvement. In addition, training on only the luminance and orientation dimensions improved performance for those conditions as well as for grouping by color, on which training had not occurred. However, improvement from partial training did not generalize to motion. Results demonstrate that a training protocol emphasizing stimulus integration enhanced perceptual grouping. Results suggest that neural mechanisms mediating grouping by common luminance and/or orientation contribute to those mediating grouping by color but do not share resources for grouping by common motion. Results are consistent with theories of perceptual learning emphasizing plasticity in early visual processing regions.     

Disrupting perceptual grouping of face parts impairs holistic face processing

Face perception is widely believed to involve integration of facial features into a holistic perceptual unit, but the mechanisms underlying this integration are relatively unknown. We examined whether perceptual grouping cues influence a classic marker of holistic face perception, the “composite-face effect.” Participants made same–different judgments about a cued part of sequentially presented chimeric faces, and holistic processing was indexed as the degree to which the task-irrelevant face halves impacted performance. Grouping was encouraged or discouraged by adjusting the backgrounds behind the face halves: Although the face halves were always aligned, their respective backgrounds could be misaligned and of different colors. Holistic processing of face, but not of nonface, stimuli was significantly reduced when the backgrounds were misaligned and of different colors, cues that discouraged grouping of the face halves into a cohesive unit (Exp. 1). This effect was sensitive to stimulus orientation at short (200 ms) but not at long (2,500 ms) encoding durations, consistent with the previously documented temporal properties of the holistic processing of upright and inverted faces (Exps. 2 and 3). These results suggest that grouping mechanisms, typically involved in the perception of objecthood more generally, might contribute in important ways to the holistic perception of faces.     

Visual grouping by motion precedes the relative localization between moving and flashed stimuli

A flashed stimulus is perceived as spatially lagging behind a moving stimulus when they are spatially aligned. When several elements are perceptually grouped into a unitary moving object, a flash presented at the leading edge of the moving stimulus suffers a larger spatial lag than a flash presented at the trailing edge (K. Watanabe. R. Nijhawan. B. Khurana, & S. Shimojo. 2001). By manipulation of the flash onset relative to the motion onset, the present study investigated the order of perceptual operations of visual motion grouping and relative visual localization. It was found that the asymmetric mislocalization was observed irrespective of physical and/or perceptual temporal order between the motion and flash onsets. Thus, grouping by motion must be completed to define the leading-trailing relation in a moving object before the visual system explicitly represents the relative positions of moving and flashed stimuli.     

Dynamic grouping and interpolation induced by flickering stimuli

A novel grouping and interpolation effect induced by flickering stimuli is described: a matrix of flickering elements forms stick-like clusters, then the clusters gradually dissociate back into the discrete elements within a few seconds. On continuous viewing, this flicker-induced grouping and interpolation repeatedly disappeared and reappeared. The perceived strength of this phenomenon peaked when the luminance of the flickering elements was alternately darker and lighter than the background; thus, the reversal of the luminance contrast polarity was responsible for flicker-induced grouping. The temporal dynamics of flicker-induced grouping showed the stochastic nature of perceptual alternation, which depended on the global structure of the stimulus. From these results, it is concluded that flicker-induced grouping reflects multiple stages of visual processing.     

Crossmodal duration perception involves perceptual grouping, temporal ventriloquism, and variable internal clock rates

Here, we investigate how audiovisual context affects perceived event duration with experiments in which observers reported which of two stimuli they perceived as longer. Target events were visual and/or auditory and could be accompanied by nontargets in the other modality. Our results demonstrate that the temporal information conveyed by irrelevant sounds is automatically used when the brain estimates visual durations but that irrelevant visual information does not affect perceived auditory duration (Experiment 1). We further show that auditory influences on subjective visual durations occur only when the temporal characteristics of the stimuli promote perceptual grouping (Experiments 1 and 2). Placed in the context of scalar expectancy theory of time perception, our third and fourth experiments have the implication that audiovisual context can lead both to changes in the rate of an internal clock and to temporal ventriloquism-like effects on perceived on- and offsets. Finally, intramodal grouping of auditory stimuli diminished any crossmodal effects, suggesting a strong preference for intramodal over crossmodal perceptual grouping (Experiment 5).     

Time course of perceptual grouping

An investigation was made of the time course of perceptual grouping that is based on two qualitatively different spatial relationships: proximity and alignment. An index of grouping capacity was used to assess the processing time required before a backward pattern mask interfered with grouping. Stimuli consisted of bistable arrays of disjunct dots that were followed by a mask. Grouping cues, either proximity or alignment, were randomly assigned to either the horizontal or vertical orientation, and subjects indicated whether the dots appeared grouped as a series of horizontal or vertical lines. Spatial metrics of the cues were systematically altered until they no longer served as a cue for grouping, thereby determining the grouping threshold. The stimulus onset asynchrony (SOA) of the mask, relative to the test stimulus, ranged from 33.3 to 150 msec. The SOA at which grouping thresholds first became elevated identified the point at which the mask first interfered with the grouping process, thereby identifying the processing time required for grouping by the specified cue. The processing time for grouping by proximity and alignment differed significantly, requiring means of 87.6 and 118.8 msec, respectively, for processing to be completed. These measurements serve to identify the processing time necessary for spatially integrating stimulus elements into unified forms, thereby delineating temporal constraints at this stage of visual processing.     

Electrophysiological evidence for a shared representational medium for visual images and visual percepts

Does mental imagery involve the activation of representations in the visual system? Systematic effects of imagery on visual signal detection performance have been used to argue that imagery and the perceptual processing of stimuli interact at some common locus of activity (Farah, 1985). However, such a result is neutral with respect to the question of whether the interaction occurs during modality-specific visual processing of the stimulus. If imagery affects stimulus processing at early, modality-specific stages of stimulus representation, this implies that the shared stimulus representations are visual, whereas if imagery affects stimulus processing only at later, amodal stages of stimulus representation, this implies that imagery involves more abstract, postvisual stimulus representations. To distinguish between these two possibilities, we repeated the earlier imagery-perception interaction experiment while recording event-related potentials (ERPs) to stimuli from 16 scalp electrodes. By observing the time course and scalp distribution of the effect of imagery on the ERP to stimuli, we can put constraints on the locus of the shared representations for imagery and perception. An effect of imagery was seen within 200 ms following stimulus presentation, at the latency of the first negative component of the visual ERP, localized at the occipital and posterior temporal regions of the scalp, that is, directly over visual cortex. This finding provides support for the claim that mental images interact with percepts in the visual system proper and hence that mental images are themselves visual representations.