Depth,size and distance in stereoscopic vision

Evidence is presented to show that in stereoscopic vision a constant ratio of perceived size to perceived distance corresponds to a constant visual angle (the size-distance invariance hypothesis). The functions relating the size/ distance ratio to visual angle and the depth/distance ratio to disparity are determined for three as using the methods of magnitude estimation and magnitude production. The results for each a may be represented by power functions, the depth/ distance function having the higher exponent. These scales are used to predict the outcome of an experiment in which depth is matched to size. The agreement of predictions with results is good for the combined data of the group, but significant deviations occur from curves predicted for individual as. An experiment in which an oblique line is matched to a frontal extent yields data consistent with Luneburg’s hypothesis that the intrinsic geometry of visual space is non-Euclidean. The indicated curvature is negative for two as and varying from positive to negative for the third.     

Apparent image rotation in stereoscopic vision: The unbalance of the pupils

In binocular vision the apparent rotation of an object relative to the frontal plane seldom corresponds with the actual rotation. The reason for this is a difference in the brightness of the object in both eyes. It can be produced by a difference in the pupil size, adaptation, or sensitivity. One of the purposes of the pupils seems to be to compensate for this brightness unbalance and to make the apparent rotation come closer to the actual one. Unbalance was produced by placing a density filter before one eye, and the corresponding rotations were then measured. The rotations are affected by the irradiation in the eye, as a physical component, but also by the lateral inhibition in the visual nervous system. If the object and the background have a different color but there is no brightness difference on the edges of the object, there is no distorted rotation.     

Perceived size and perceived distance in stereoscopic vision and an analysis of their causal relations

Effects of visual angle and convergence upon the perceived sizes and perceived distances of a familiar object (playing card) and a nonrepresentational object (blank white card) were investigated by means of a projector stereoscope with polarizing filters. The results obtained with six Ss indicated that size estimates increased nearly proportionally as the visual angle increased and decreased nearly linearly as the convergence increased. Distance estimates decreased nearly linearly as either the visual angle or the convergence increased. The ratio of the size estimate to the distance estimate for a given visual angle was almost constant irrespective of convergence. In this sense, the size-distance invariance hypothesis held. No clear effect of familiarity was found. Partial correlations were used to discriminate direct and indirect causal relationships between the stimulus variables and perceptual estimates. Both perceived size and perceived distance were found to be determined directly by the two stimulus variables, but to be mutually related only indirectly.     

The stereoscopic sliver: a comparison of duration thresholds for fully stereoscopic and unmatched versions

Just as positional disparities of image features seen with both eyes provide depth information, the presence of an area visible to one eye but not the other within a binocularly viewed scene can indicate an occlusion at a depth discontinuity. The close geometrical association between these two kinds of cues suggests they may both be exploited by stereopsis. To investigate this, we developed a novel binocular stimulus entirely lacking in classical disparity that contains an unmatched vertical sliver which elicits a warping of the surrounding surface to accommodate a depth discontinuity. We measured depth-discrimination performance at a range of stimulus durations, correcting for variations in stimulus visibility, to characterise the decline of the efficacy of the depth signal with limited integration time. Results show a close correspondence of performance for similar stimuli with unmatched features and classical binocular disparity across a sixtyfold range of viewing durations, supporting the notion of a close association between the two types of cues in human stereopsis. Control experiments excluded simple eye-of-origin cues and long-range false matches as explanatory factors.     

Development of visual attention: a stereoscopic view

Five-year-olds, 8-year-olds, and adults (20 each) tachistoscopically viewed random-dot stereograms containing either uniform depth or an elevated disk whose perimeter fell 1.5 degrees, 2.5 degrees, or 4 degrees beyond fixation. When subjects were forewarned as to the size of the disk to look for (precued trials), signal detection improved (d' increased) for all three groups, and 5-year-olds improved the most. Without forewarning (self-cued trials), the 5-year-olds performed more poorly than the other two groups, which performed alike. Although young children are able to allocate their visual attention selectively, they do not appear to deploy it as quickly or as effectively as their elders when the focus of attention is theirs to choose.     

The relation between electroencephalogram asymmetry and attention biases to threat at baseline and under stress

Electroencephalogram (EEG) asymmetry in the alpha frequency band has been implicated in emotion processing and broad approach-withdrawal motivation systems. Questions remain regarding the cognitive mechanisms that may help elucidate the observed links between EEG asymmetry and patterns of socioemotional functioning. The current study observed frontal EEG asymmetry patterns at rest and under social threat among young adults (N = 45, M = 21.1 years). Asymmetries were, in turn, associated with performance on an emotion-face dot-probe attention bias task. Attention biases to threat have been implicated as potential causal mechanisms in anxiety and social withdrawal. Frontal EEG asymmetry at baseline did not predict attention bias patterns to angry or happy faces. However, increases in right frontal alpha asymmetry from baseline to the stressful speech condition were associated with vigilance to angry faces and avoidance of happy faces. The findings may reflect individual differences in the pattern of response (approach or withdrawal) with the introduction of a mild stressor. Comparison analyses with frontal beta asymmetry and parietal alpha asymmetry did not find similar patterns. Thus, the data may reflect the unique role of frontal regions, particularly the dorsolateral prefrontal cortex, in cognitive control and threat detection, coupled with ruminative processes associated with alpha activity.     

Center-of-inattention: Position biases in decision-making

This paper examines centrality of physical position as a cue that leads to systematic biases in people’s decisions to retain or eliminate a participant from a group. Termed the “center-stage” effect, we argue that people use their belief that “important people sit in the middle” as a schematic cue that they substitute for individuating performance information for individuals who occupy central positions when the goal is to eliminate all but one of the group members. This leads to the errors of those in center-positions being overlooked: or making them the “centers-of-inattention.” Study 1 examines people’s lay beliefs regarding positions using two stylized placement tasks (a group interview and classroom seating scenarios). These suggest that people believe that more attention is paid to those in the center than those on the extremes. Study 2 tests the center-stage effect using observational data from a real television show, The Weakest Link. Results show that players assigned at random to central positions are more likely to win the game than those in extreme positions. Study 3, a laboratory experiment manipulating attention paid to the game shows that observers overlook the errors of players in the center to a greater extent than the errors of players in extreme positions. Study 4 replicates the game in the laboratory with direct process measures to show that players playing the game make the same error. Study 5 shows that in a stylized group interview setting, participants who believe that “important people sit in the middle” find the performance of candidates in the extreme position easier to recall than the performance of those in the central position, and are more likely to choose them. Study 6 shows that the “center-stage” effects are weaker when the end-game rule allows for two (vs one) contestants to be retained. Overall results converge to show that the use of the “center-stage” heuristic substitutes for the effortful processing of individuating information, leading to a biased (favorable) assessment of people in the center. Implications for decision-making are discussed.     

Attentional and interpretative biases in appearance concern: An investigation of biases in appearance-related information processing

The present study examined associations between high levels of appearance concern and information processing biases in interpretation and attention. An opportunity sample (N = 79) categorised ambiguous stimuli as related or unrelated to appearance. Participants then responded to the same stimuli in a modified visual dot-probe task assessing attentional bias. Participant responses were assessed in relation to level of appearance concern. The results indicated a valence specific bias towards interpretation of ambiguous stimuli as negative and appearance-related in individuals with higher levels of concern. There was also evidence of attentional bias towards information perceived as appearance-related in participants with higher levels of appearance concern. The study findings suggest that association between appearance-orientated information processing biases and level of appearance concern; this association may lead to mutually reinforcing bias and concern.     

Implicit interpretation biases affect emotional vulnerability: a training study

Cognitive theories of emotion propose that the interpretation of emotion-eliciting situations crucially shapes affective responses. Implicit or automatic biases in these interpretations may hinder emotion regulation and thereby increase risk for the onset and maintenance of psychological disorders. In this study, participants were randomly assigned to a positive or negative interpretation bias training using ambiguous social scenarios. After the completion of the training, a stress task was administered and changes in positive and negative affect and self-esteem were assessed. The results demonstrate that the interpretation bias training was successful in that participants exhibited a tendency to interpret novel scenarios in accordance with their training condition. Importantly, the positive training condition also had a protective effect on self-esteem. Participants in this condition did not exhibit a decrease in self-esteem after the stress task, whereas participants in the negative condition did. These results demonstrate that implicit cognitive biases can be trained and that this training affects self-esteem. Implications of these findings for research on psychopathology and emotion regulation are discussed.     

The foreign-language effect: thinking in a foreign tongue reduces decision biases

Would you make the same decisions in a foreign language as you would in your native tongue? It may be intuitive that people would make the same choices regardless of the language they are using, or that the difficulty of using a foreign language would make decisions less systematic. We discovered, however, that the opposite is true: Using a foreign language reduces decision-making biases. Four experiments show that the framing effect disappears when choices are presented in a foreign tongue. Whereas people were risk averse for gains and risk seeking for losses when choices were presented in their native tongue, they were not influenced by this framing manipulation in a foreign language. Two additional experiments show that using a foreign language reduces loss aversion, increasing the acceptance of both hypothetical and real bets with positive expected value. We propose that these effects arise because a foreign language provides greater cognitive and emotional distance than a native tongue does.     

Interpretive biases in chronic insomnia: an investigation using a priming paradigm

Disorder-congruent interpretations of ambiguous stimuli characterize several psychological disorders and have been implicated in their maintenance. Models of insomnia have highlighted the importance of cognitive processes, but the possibility that biased interpretations are important has been minimally investigated. Hence, a priming methodology was employed to investigate the presence of an interpretive bias in insomnia. A sample of 78 participants, differing in the presence of a diagnosis of insomnia, severity of sleep disturbance, and sleepiness, was required to read ambiguous sentences and make a lexical decision about target words that followed. Sleepiness at the time of the experiment was associated with the likelihood with which participants made insomnia and threat consistent interpretations of ambiguous sentences. The results suggest that there is a general bias towards threatening interpretations when individuals are sleepy and suggests that cognitive accounts of insomnia require revision to include a role for interpretative bias when people are sleepy. Future research is required to investigate whether this interpretive bias plays a causal role in the maintenance of insomnia.     

Rightward biases in free-viewing visual bisection tasks: implications for leftward responses biases on similar tasks

Neurologically normal individuals exhibit strong leftward response biases during free-viewing perceptual judgments of brightness, quantity, and size. When participants view two mirror-reversed objects and they are forced to choose which object appears darker, more numerous, or larger, the stimulus with the relevant feature on the left side is chosen 60-75% of the time. This effect could be influenced by inaccurate judgments of the true centre-point of the objects being compared. In order to test this possibility, 10 participants completed three visual bisection tasks on stimuli known to elicit strong leftward response biases. Participants were monitored using a remote eye-tracking device and instructed to stare at the subjective midpoint of objects presented on a computer screen. Although it was predicted that bisection errors would deviate to the left of centre (as is the case in the line bisection literature), the opposite effect was found. Significant rightward bisection errors were evident on two of the three tasks, and the leftward biases seen during forced-choice tasks could be the result of misjudgments to the right of centre on these same tasks.     

Subjective contours in stereoscopic space

Stereoscopic depth and subjective contour clarity were manipulated by varying the type of monocular configuration as well as magnitude and direction of disparity. The clarity of the subjective contours was influenced significantly by both magnitude and direction of disparity and by the type of monocular configuration. Subjective contours were always less clear when the objective monocular contour was discontinuous regardless of disparity. Stereoscopic depth estimates varied directly with magnitude and direction of disparity; however, depth magnitude reports were truncated when the disparity was carried by discontinuously defined patterns.