Lateral biases in assumptions of lighting position

People presume that the light source in pictures comes from above, and there is some evidence that this phenomenon also demonstrates lateral biases. When investigators present multiple ambiguous stimuli or visually complex objects, people assume that the source of light is from above, and to the left. However, when single relatively simple stimuli are presented, this lateral bias is not readily observed. To investigate whether lateral bias is dependent on the number of stimuli presented, the present experiment employs a within-subjects design to present single spheres or pairs of spheres. Contrary to our expectations, leftward biases were exhibited in both the single-sphere condition and the paired-spheres condition. Single spheres that were lit from the left were more likely to be judged as convex than comparable spheres lit from the right. Similarly, when pairs of laterally lit spheres were presented and participants were asked to judge which sphere appeared to be more convex, participants chose spheres lit from the left regardless of the angle of illumination. Collectively, these results suggest that there are lateral biases in assumptions of illumination position and that these biases do not depend on the number of stimuli being perceived at any given time.     

“Where is the sun” for hemi-neglect patients?

Human observers use prior constraints to disambiguate a scene; in particular, light is preferentially seen as coming from above but also slightly from the left. One explanation of this lateral bias could be a cerebral hemispheric difference. The aim of the present study was to determine the preferred light source position for neglect patients. For this purpose, we used the ambiguous shaded “Polo Mint” stimulus, a ring divided into eight equal sectors. All sectors but one were the same shape, convex or concave, as determined by the light source position. Participants had to report the side (left or right) of the odd sector or, in a separate experiment, to report its shape (convex or concave). Eight patients with spatial neglect (left neglect N = 7, right neglect N = 1) after a right or left temporo-parietal or thalamic lesion and 14 control participants ran the experiment. Left neglect patients showed a significantly different light bias from the bias observed for controls and for the right neglect patient (i.e., a reduction of the left bias or a right bias rather than a left bias). We conclude that some disabilities presented by patients with spatial neglect may be due to difficulties processing information that is not present in the visual field or imagined in the representational scene.     

Selective attention and avoidance on a pictorial cueing task during stress in clinically anxious and depressed participants

Although it is well established that attentional biases exist in anxious populations, the specific components of visual orienting towards and away from emotional stimuli are not well delineated. The present study was designed to examine these processes. We used a modified spatial cueing task to assess the speed of engagement and disengagement from supraliminal and masked pictorial cues depicting threat, dysphoria, or neutral content in 36 clinically anxious, 41 depressed and 41 control participants. Participants were randomly assigned to a stress or neutral condition. During stress, anxious participants were slow to disengage from masked left hemifield pictures depicting threat or dysphoria, but were quick to disengage from supraliminal threat pictures. Information processing in anxious participants during stress was characterized by early selective attention of emotional stimuli, occurring prior to full conscious awareness, followed by effortful avoidance of threat. Depressed participants were distinct from the anxious group, displaying selective attention for stimuli depicting dysphoria, but not threat, during the neutral condition. In sum, attentional biases in clinical populations are associated with difficulties in the disengagement component of visual orienting. Further, a vigilant-avoidant pattern of attentional bias may represent a strategic attempt to compensate for the early activation of a fear response.     

Free viewing perceptual asymmetries for judgment of brightness and quantity: dependence on stimulus orientation

Previous research has indicated that normals exhibit strong leftward biases during free-viewing perceptual judgments of brightness and quantity. When participants view two symmetrical objects and they are forced to choose which object appears darker or more numerous, participants usually select the stimulus with the relevant feature on the left side. The present study investigated the possibility that these perceptual asymmetries are dependent on scanning a stimulus horizontally across the midline by administering a task with two rectangular reversed stimuli presented either horizontally or vertically. When the stimuli were presented horizontally (crossing the midline), participants exhibited leftward biases, but these biases disappeared when the stimuli were presented vertically. This result supports the position that free-viewing perceptual asymmetries are dependent on scanning the stimuli across the midline.     

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。     

低自尊个体注意偏向的ERP研究

本研究以高兴、愤怒和中性面孔图片为实验材料,采用空间线索任务,借助事件相关电位技术(ERP)探讨低自尊个体注意偏向的内在机制及生理基础,即从电生理的角度,探讨注意偏向的内在机制是反映了注意的快速定向还是注意的解脱困难,亦或是既有快速注意定向又伴随注意的解脱困难。行为数据发现,高低自尊个体在有效提示下的反应显著快于无效提示条件。脑电数据发现,无效提示条件下,愤怒面孔后的靶子比高兴和中性面孔后的靶子在低自尊个体中诱发了更大的P1和更小的N1波幅,有效提示下无显著差异;高自尊个体在N1和P1波幅上无显著结果。晚期P300成分上,无效提示比有效提示诱发了更正的波幅,未发现自尊相关的显著差异。结果表明,低自尊个体对评价性威胁信息(愤怒)的注意偏向是对威胁信息(愤怒)的注意解脱困难。     

Multitask investigation of individual differences in hemispheric asymmetry

Right-handed subjects (N = 120) participated in four different laterality tasks designed to measure aspects of cerebral hemisphere asymmetry: identification of dichotically presented consonant-vowel syllables (CVs), examination of the effects of concurrent repetition of CVs and concurrent anagram solution on finger-tapping by the right and left hands, lateralized identification of CVs presented tachistoscopically to the left and right visual fields, and left/right biases on a free-vision face task involving judgments of emotion. Ear differences in the dichotic listening task were related to the pattern of lateralized interference in the dual-task finger-tapping paradigm. There were no other significant relations between pairs of tasks, but when the present results are considered in the light of other recent experiments, there appears to be a relation between lateral bias on the free-vision face task and visual field differences in tachistoscopic identification. The pattern of results has implications for hypothesized individual differences among right-handers in cerebral dominance for verbal processes, input pathway dominance, and asymmetric arousal of the two cerebral hemispheres.     

Young infants’ sensitivity to shading stimuli with radial motion1

Abstract: The purpose of this study was to examine 5‐month‐old infant's sensitivity to a shading cue with radial motion. Our stimuli were radially expanding or contracting circles with vertical or horizontal shadings. We tested infants’ preference for vertical (top‐ and bottom‐lit) and horizontal (left‐ and right‐lit) shadings. The results indicate that infants tested with the vertical shading showed significant preference for the top‐lit shading, whereas infants tested with the horizontal shading did not show any significant preference. The fact that the significant preference was observed only in the vertical shading condition suggests that 5‐month‐old infants might use shading information on the basis of the “light‐from‐above assumption.” We revealed that even 5‐month‐old infants are sensitive to shading information when they are exposed to shading stimuli with radial motion.     

Coherence and specificity of information-processing biases in depression and social phobia

Research has not resolved whether depression is associated with a distinct information-processing bias, whether the content of the information-processing bias in depression is specific to themes of loss and sadness, or whether biases are consistent across the tasks most commonly used to assess attention and memory processing. In the present study, participants diagnosed with major depression, social phobia, or no Axis I disorder, completed several information-processing tasks assessing attention and memory for sad, socially threatening, physically threatening, and positive stimuli. As predicted, depressed participants exhibited specific biases for stimuli connoting sadness; social phobic participants did not evidence such specificity for threat stimuli. It is important to note that the different measures of bias in memory and attention were not systematically intercorrelated. Implications for the study of cognitive bias in depression, and for cognitive theory more broadly, are discussed.     

No effect of synesthetic congruency on temporal ventriloquism

A sound presented in temporal proximity to a light can alter the perceived temporal occurrence of that light (temporal ventriloquism). Recent studies have suggested that pitch-size synesthetic congruency (i.e., a natural association between the relative pitch of a sound and the relative size of a visual stimulus) might affect this phenomenon. To reexamine this, participants made temporal order judgements about small- and large-sized visual stimuli while high- or low-pitched tones were presented before the first and after the second light. We replicated a previous study showing that, at large sound-light intervals, sensitivity for visual temporal order was better for synesthetically congruent than for incongruent pairs. However, this congruency effect could not be attributed to temporal ventriloquism, since it disappeared at short sound-light intervals, if compared with a synchronous audiovisual baseline condition that excluded response biases. In addition, synesthetic congruency did not affect temporal ventriloquism even if participants were made explicitly aware of congruency before testing. Our results thus challenge the view that synesthetic congruency affects temporal ventriloquism.     

Perceptual biases in the horizontal and vertical dimensions are driven by separate cognitive mechanisms

Perceptual attention in healthy participants is characterized by two biases, one operating in the horizontal plane, which draws attention leftward, and the other operating in the vertical plane, which draws attention upward. Given that these biases are reliably found in the same individual, and appear similar at a surface level, a number of researchers have investigated the relationship between horizontal and vertical attentional biases. To date, these investigations have failed to find an association, and this may be due to the fact that one-dimensional vertical and horizontal stimuli were presented separately rather than being measured from a single, two-dimensional stimulus. Across three experiments, two dimensional stimuli were presented, and participants marked the centre of the stimuli. In addition, the shapes of the stimuli were manipulated to determine whether this produced the same modulation of the two biases. Across 13 stimuli and three experiments there were no correlations between the vertical and horizontal biases. In addition, manipulations of stimulus shape, which affected biases in one dimension, did not affect biases in the other dimension. There were, however, consistent correlations between the degree of bias within each dimension across the different stimuli. This study has produced converging evidence that horizontal and vertical biases in spatial judgments rely on separate cognitive mechanisms. To account for these results we discuss a model whereby horizontal asymmetries rely more on space-based mechanisms whereas vertical asymmetries rely more on object-based mechanisms.     

Cognitive bias and emotion in neuropsychological models of depression

Neuropsychological models of depression were tested by examining encoding and recognition biases elicited by emotional stimuli manifested in regional brain wave activity. Participants were pre-exposed to emotional stimuli. These stimuli were presented again embedded in new stimuli, and event-related brain potentials (ERPs) were recorded while participants judged whether they had viewed each stimulus previously. Controls showed an enhanced P300 during encoding and reduced P300 during recognition of positive stimuli, indicating a response bias for positive information. In contrast, participants diagnosed with major depression showed no valence difference during encoding of new stimuli or recognition of old stimuli. These results suggest positive cognitive biases in controls and a lack of such a biases in depressed individuals. Additionally, regression analyses demonstrated that a substantial proportion of P300 variance was related to clinical scale     

Material-illumination ambiguities and the perception of solid objects

The appearance of objects depends on their material, shape, and on the illumination conditions. Conversely, object appearance provides us with cues about the illumination and the material. This so-called inverse problem is basically underdetermined and therefore we expect that material and illumination perception are confounded. To gain insight into the relevant mechanisms, we rendered a set of artificial spheres for vastly different canonical light fields and reflectance functions. We used four physics-based bidirectional reflectance distribution functions (BRDFs) representing glossy, pitted, velvety, and matte material. The six illumination conditions were collimated illumination from four directions, hemispherical diffuse illumination, and fully diffuse (Ganzfeld) illumination. In three sub-experiments we presented pairs of stimuli and asked human observers to judge whether the material was the same, whether the illumination was the same, and for a subset in which either the illumination or the material was the same to judge which of the two was constant. We found that observers made many errors in all sub-experiments. In experiment 2 the illumination direction was chosen at random. Using an interactive interface, we asked human observers to match the illumination direction of a sphere of one of the four materials with that of a Lambertian sphere. We found systematical material-dependent deviations from veridical performance. Theoretical analysis of the radiance patterns suggests that judgments were based mainly on the position of the shadow edge. In conclusion, we found no evidence for 'material constancy' for perception of smooth rendered spheres despite vast quantitative and qualitative differences in illumination and in BRDF between the stimuli. Although human observers demonstrated some 'illumination constancy', they made systematic errors depending on the material reflectance, suggesting that they used mainly the location of the shadow edge. Our results suggest that material perception and light-field perception are basically confounded.     

Attentional bias to angry faces using the dot-probe task? It depends when you look for it

A number of studies using the dot-probe task now report the existence of an attentional bias to angry faces in participants who rate highly on scales of anxiety; however, no equivalent bias has been observed in non-anxious populations, despite evidence to the contrary from studies using other tasks. One reason for this discrepancy may be that researchers using the dot-probe task have rarely investigated any effects which might emerge earlier than 500 ms following presentation of the threat-related faces. Accordingly, in the current study we presented pairs of face stimuli with emotional and neutral expressions and probed the allocation of attention to these stimuli for presentation times of 100 and 500 ms. Results showed that at 100 ms there was an attentional bias towards the location of the relatively threatening stimulus (the angry face in angry/neutral pairs and the neutral face in neutral/happy pairs) and this pattern reversed by 500 ms. Comparisons of reaction time (RT) scores with an appropriate baseline suggested that the early bias toward threatening faces may actually arise through inhibition of the relatively least threatening member of a face pair rather than through facilitation of, or vigilance towards, the more threatening stimulus. However the mechanisms governing the observed biases are interpreted, these data provide evidence that probing for the location of spatial attention at 500 ms is not necessarily indicative of the initial allocation of attention between competing emotional facial stimuli.     

Time course of attentional bias for fear-relevant pictures in spider-fearful individuals

The time course of attentional biases for spider stimuli was assessed in two groups of individuals with high or low levels of spider fear. Pairs of photographs of spiders and cats were presented in a visual probe task with three exposure durations: 200, 500 and 2000 ms. Results indicated greater attentional bias for spider stimuli in high fear, than in low fear, individuals in the 200 ms condition. The attentional bias in the high fear group significantly reduced as stimulus exposure duration increased, with no significant biases found in the longer exposure conditions. Results support the view that high fear is associated with an enhanced initial attentional bias for fear-relevant stimuli, but that this attentional bias is not maintained over time.     

Selective attention, visual laterality, awareness, and perceiving the meaning of parafoveally presented words

Four experiments are reported investigating the effect of selective attention on the semantic encoding of parafoveally presented words. In Experiments 1 and 2 a right visual field (RVF) performance bias was found when subjects attended to words that could appear either left or right of centre (attend-side condition). When subjects attended centrally and ignored lateral distractor words (attendcentre condition) there was an inhibitory effect of word meaning from left visual field (LVF) distractors. Both inhibitory and facilitatory effects of semantic category were observed from unattended words in Experiments 3 and 4. The pattern of effects depended upon the direction of spatial bias in an attend-side condition. Both kinds of effect occurred even for subjects who were unable to make consciously directed semantic category decisions to words at the same eccentricity (4°) and exposure time (15 msec) as ignored distractors in the attend-centre condition. Implications of these findings for theories of selective attention, for the issue of semantic encoding independent of conscious awareness, and for theories of the relationship between lateral performance biases and functional hemispheric asymmetry are discussed.     

Footprints sticking out of the sand. Part 1: Children's perception of naturalistic and embossed symbol stimuli

The shading information in images that depict surfaces of three-dimensional objects cannot be perceived correctly unless the direction of the illuminating light source is known, and, in the absence of this knowledge, adults interpret such images by assuming that light comes from above. In order to investigate if children make use of a similar assumption, we analysed data from 171 children between the ages of 4.6 and 10.8 years using 10 images (shown upright and upside-down) that could be perceived as either convex or concave. Each of five images depicted a naturalistic picture (e.g., a footprint), each of the other five depicted an embossed symbol (e.g., a square). On each of 20 trials, a child was presented with either an upright or upside-down image, and indicated whether the depicted shape appeared convex or concave. Our main findings are that (i) naturalistic stimuli are significantly more likely to be perceived as if light comes from above than symbol stimuli, and (ii) children's propensity to interpret stimuli as if light comes from above increases significantly with age, and at a similar rate for naturalistic and symbol stimuli. These results suggest that, irrespective of any innate competence, children's ability to interpret shading information is gradually refined throughout childhood.     

Money talks in attention bias modification: Reward in a dot-probe task affects attentional biases

Attention bias modification (ABM) aimed at correcting dysfunctional biases in anxiety patients has met with only mild success. Inspired by recent studies showing large effects of financial reward upon attention shifts, we contrasted effects of traditional dot-probe ABM and reward upon attention biases in a between-subject 2 × 2 design. Twenty-seven participants in group cognitive behavioural therapy (GCBT) for social anxiety disorder (SAD) were randomly assigned to undergo six sessions of a dot-probe task consisting of ABM or placebo ABM along with random or high reward following neutral stimuli. There was no influence of ABM on participants' attention bias over and above the influence of GCBT. Reward, however, had a strong influence on attention bias. Neither ABM nor reward reduced SAD symptoms over and above the effects of GCBT. The results add to the growing evidence that benefits of ABM through dot-probe training are unreliable but suggest on the other hand that rewarding attention may strongly influence dysfunctional attention biases.     

Fear of negative evaluation and attentional bias for facial expressions: An event-related study

Numerous studies have shown an exacerbation of attentional bias towards threat in anxiety states. However, the cognitive mechanisms responsible for these attentional biases remain largely unknown. Further, the authors outline the need to consider the nature of the attentional processes in operation (hypervigilance, avoidance, or disengagement). We adapted a dot-probe paradigm to record behavioral and electrophysiological responses in 26 participants reporting high or low fear of evaluation, a major component of social anxiety. Pairs of faces including a neutral and an emotional face (displaying anger, fear, disgust, or happiness) were presented during 200 ms and then replaced by a neutral target to discriminate. Results show that anxious participants were characterized by an increased P1 in response to pairs of faces, irrespective of the emotional expression included in the pair. They also showed an increased P2 in response to angry–neutral pairs selectively. Finally, in anxious participants, the P1 response to targets was enhanced when replacing emotional faces, whereas non-anxious subjects showed no difference between the two conditions. These results indicate an early hypervigilance to face stimuli in social anxiety, coupled with difficulty in disengaging from threat and sustained attention to emotional stimuli. They are discussed within the framework of current models of anxiety and psychopathology.     

The influence of autism-like traits on cheek biases for the expression and perception of happiness

People with autism show attenuated cerebral lateralisation for emotion processing. Given growing appreciation of the notion that autism represents a continuum, the present study aimed to determine whether atypical hemispheric lateralisation is evident in people with normal but above average levels of autism-like traits. One hundred and twenty-seven right-handed participants (M = 43, F = 84) completed the AQ questionnaire (Baron-Cohen, Wheelwright, Skinner, Martin, & Clubley, 2001), and then (a) posed for a photo expressing happiness, and (b) viewed pairs of left and right cheek poses, making a forced-choice decision indicating which image appeared happier (half the images were mirror-reversed to control for perceptual biases). Results indicated that irrespective of AQ status, people were intuitively aware that the left cheek is more emotionally expressive: participants offered the left cheek when posing to appear happy, and perceived left poses as happier than right poses. As the left cheek is predominantly controlled by the right hemisphere, these findings strongly support the right hemisphere hypothesis. The fact that people with normal but above average levels of autism-like traits did not show a reduced leftward bias for either task indicates that the attenuated emotion lateralisation pattern noted in the clinical population does not extend into the normal spectrum. Instead, the results suggest that people with normal but above average levels of AQ traits are as sensitive to the silent social/emotional cues signalled by a left cheek pose as those with lower AQ scores.