掩蔽刺激对目标识别加工的作用：来自fNIRS的证据

信息掩蔽刺激(如随机字母群)对字母视觉搜索的干扰大于能量掩蔽刺激(如将字母群像素随机化后的散点), 但相应的中枢机理还不清楚。本研究采用记录脑代谢激活模式的功能性近红外光学脑成像技术(fNIRS), 考察年轻成年被试分别在字母掩蔽、字母碎片掩蔽、像素掩蔽条件下判断上、下、左、右四个目标字母是否相同时的大脑皮层氧合血红蛋白浓度的变化。结果显示, 依字母、字母碎片、随机散点掩蔽条件顺序, 被试的搜索任务成绩显著递增, 而顶-枕皮层的激活范围与程度显著递减, 表明信息掩蔽较匹配的能量掩蔽对视觉搜索有更大的干扰作用, 并在初级和联合视觉皮层引发更大的激活。在字母碎片掩蔽条件下, 视觉初级皮层部分区域的激活水平与搜索行为绩效的相关显著, 而在字母掩蔽条件下, 视觉联合皮层部分区域的激活水平与搜索行为绩效的相关显著。这进一步说明信息掩蔽中的字母掩蔽和字母碎片掩蔽的掩蔽作用在大脑皮层上所造成的加工负载存在差异。     

Selective attention fails to alter the dichotic listening lag effect: evidence that the lag effect is preattentional

Berlin et al. (1973) reported that either stimulus from a dichotic pair of consonant-vowel syllables is processed preferentially when its presentation is delayed by 30-60 ms. In the first of three experiments with 60 normal right-handed adults, we replicated the Berlin et al. "lag effect," but only for asynchronies between 60 and 90 ms. In Experiment 2 subjects focused attention selectively on one ear. The results indicated that focused attention and stimulus asynchrony have additive effects: Performance improved at the attended ear irrespective of stimulus asynchrony, but the lag effect remained unchanged relative to the divided-attention condition. Experiment 3 entailed a signal detection task that allowed separate analysis of detection and localization accuracy. As in previous studies, selective attention to one ear increased the accuracy of localization but not detection at the attended ear. Both dependent measures indicated a lag effect that remained invariant as attention was manipulated. These findings imply that the lag effect is attributable to a preattentional stage of auditory processing.     

Masking the face: Recognition of emotional facial expressions as a function of the parameters of backward masking

Four experiments are reported investigating recognition of emotional expressions in very briefly presented facial stimulus. The faces were backwardly masked by neutral facial displays and recognition of facial expressions was analyzed as a function of the manipulation of different parameters in the masking procedure. The main conclusion was that stimulus onset asynchrony between target and mask proved to be the principal factor influencing recognition of the masked expressions. In general, confident recognitions of facial expressions required about 100–150 msec, with shorter time for happy than for angry expressions. The manipulation of the duration of both the target and the mask, by itself, had only minimal effects.     

Backward masking: evidence of reduced subcortical amygdala engagement in autism

Recent data suggest that subthreshold presentation of emotional information is relayed to the amygdala along subcortical pathways. We examined the effect of backward masked neutral and anxious faces on the social decisions of a group of high functioning children with autism ages 7-13 years and matched controls. Participants were asked to select the friendliest of two faces, one of which was associated with the subthreshold (33 ms) presentation of an anxious face (A/N) and the other a subthreshold neutral face (N/N). Neutral paired faces were selected more often than A/N paired faces by both groups. However, children with autism selected significantly fewer N/N stimuli and more A/N stimuli than controls. These results suggest that the social choices of children with autism were influenced less by emotional information presented subconsciously and suggest a subcortical contribution to the social/emotional processing deficits observed in autism.     

阅读知觉广度研究中掩蔽刺激干扰效应的眼动研究

本研究对汉语阅读知觉广度研究中掩蔽刺激的干扰效应进行了探讨。两个实验分别以大学生为被试,采用单因素实验设计,探测了汉语阅读眼动研究中移动窗口范式和中央凹掩蔽范式下四种掩蔽条件(星号掩蔽、繁体字掩蔽、相似汉字掩蔽和控制条件)的干扰作用。两个实验比较一致的支持了在两种范式呈现条件下星号掩蔽材料的干扰效应较小,而繁体字和相似汉字的干扰效应较大。     

汉语双字词句知觉广度的眼动研究

阅读知觉广度通常指阅读者在阅读文本过程中每次注视能获取有用视觉信息的范围。既往的汉语知觉广度的研究一般把单字作为基本的知觉呈现单元,但在某些呈现条件下,此类呈现方式会导致阅读过程中的语义加工的完整性被破坏。本研究采用眼动追踪技术,使用移动窗口范式和中央凹掩蔽范式,使用双字词句作为阅读材料,双字词作为基本的知觉呈现单元,探讨在保证知觉呈现单元语义完整性的基础上大学生的汉语阅读知觉广度。实验一采用移动窗口范式,结果发现,知觉广度范围为注视词左侧1个双字词及右侧1-2个双字词的空间。实验二采用中央凹掩蔽范式,结果验证了实验一的研究结果。该结果表明,在汉语阅读过程中,以双字词为基本的视觉呈现单元,较既往研究中单字为基本呈现单元的情况,更好地保证了阅读中语义的完整性,从而获得了更大的知觉范围。该结果建立于视觉呈现单元的语义完整性的基础上,是对现有的汉语阅读知觉广度理论的完善和扩展。     

The role of convexity in perception of symmetry and in visual short-term memory

Visual perception of shape is affected by coding of local convexities and concavities. For instance, a recent study reported that deviations from symmetry carried by convexities were easier to detect than deviations carried by concavities. We removed some confounds and extended this work from a detection of reflection of a contour (i.e., bilateral symmetry), to a detection of repetition of a contour (i.e., translational symmetry). We tested whether any convexity advantage is specific to bilateral symmetry in a two-interval (Experiment 1) and a single-interval (Experiment 2) detection task. In both, we found a convexity advantage only for repetition. When we removed the need to choose which region of the contour to monitor (Experiment 3) the effect disappeared. In a second series of studies, we again used shapes with multiple convex or concave features. Participants performed a change detection task in which only one of the features could change. We did not find any evidence that convexities are special in visual short-term memory, when the to-be-remembered features only changed shape (Experiment 4), when they changed shape and changed from concave to convex and vice versa (Experiment 5), or when these conditions were mixed (Experiment 6). We did find a small advantage for coding convexity as well as concavity over an isolated (and thus ambiguous) contour. The latter is consistent with the known effect of closure on processing of shape. We conclude that convexity plays a role in many perceptual tasks but that it does not have a basic encoding advantage over concavity.     

Perception of Genuine and Masking Smiles in Children and Adults: Sensitivity to Traces of Anger

The authors examined children's and adults' sensitivity to traces of anger in masking smiles by presenting participants with short video excerpts of smiles that differed by the intensity of an anger component. Fifty-two children, aged 6 to 12 years, and 26 adults were asked to judge whether a stimulus person was really happy or pretending to be happy. Six- and 7-year-old children were found to be sensitive to traces of anger, but less so than older children and adults. Researchers found evidence of explicit knowledge of the emotion hidden in masking smiles only in adult participants.     

Local Dynamic Stability of the Locomotion of Lower Extremity Joints and Trunk During Backward Upslope Walking

Backward slope walking was considered as a practical rehabilitation and training skill. However, its gait stability has been hardly studied, resulting in its limited application as a rehabilitation tool. In this study, the effect of walking direction and slope grade were investigated on the local dynamic stability of the motion of lower extremity joints and trunk segment during backward and forward upslope walking (BUW/FUW). The local divergence exponents (λ_S) of 16 adults were calculated during their BUW and FUW at grades of 0%, 5%, 10%, and 15%. Mean standard deviation over strides (MeanSD) was analyzed as their gait variability. Backward walking showed larger λ_S for the abduction-adduction and rotational angles of knee and ankle on inclined surface than forward walking, while λ_S for hip flexion-extension angle at steeper grades was opposite. No grade effect for any joint existed during BUW, while λ_S increased with the increasing grade during FUW. As to the trunk, walking direction did little impact on λ_S. Still, significant larger λ_S for its medial-lateral and vertical motion were found at the steeper grades during both FUW and BUW. Results indicate that during BUW, the backward direction may influence the stability of joint motions, while the trunk stability was challenged by the increasing grades. Therefore, BUW may be a training tool for the stability of both upper and lower body motion during gait.     

Involuntary attention in the absence of visual awareness

ABSTRACT

Previous studies have found a dissociation between voluntary attention and awareness. Here, we examined the relationship between involuntary attention and awareness. We presented a masked cue such that participants were unaware of the cue. This was followed by a search array, for which participants detected the presence of a shape target. Even though the cue was task irrelevant and unconscious, we observed faster reaction times when either the cue’s location or colour was congruent with shape target. We conclude an unconscious stimulus can elicit both space- and feature-based attention. These results provide further evidence for the dissociation between attention and consciousness.