Hemispheric asymmetries for global and local visual perception: Effects of stimulus and task factors.

Although neurological and physiological studies indicate a right hemisphere superiority in global processing and a left hemisphere superiority in local processing of Navon-type hierarchical letters (D. Navon, 1977), most investigations of lateralized perception in healthy participants report neither asymmetry. In 6 experiments the authors examined the influence of attentional demands, stimulus properties, and mode of response on perceptual asymmetries for global and local perception. Consistent with their theoretical predictions, asymmetries were more robust on divided- than focused-attention tasks and in response to stimuli in which local and global levels were equally salient compared with those with greater global than local saliency. Contrary to their prediction, perceptual asymmetries were not influenced by the complexity of the motor response. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Aging and the perceptual organization of 3-D scenes.

In the current study, the authors investigated whether the ground dominance effect (the use of ground surface information for the perceptual organization of scenes) varied with age. In Experiment 1, a scene containing a ground, a ceiling, and 2 vertical posts was presented. The scene was either in its normal orientation or rotated to the side. In Experiment 2, a blue dot was attached to each post, with location varied from bottom to top of the posts. In Experiment 3, a scene similar to that in Experiment 1 was presented in different locations in visual field. Observers judged which of the 2 objects (posts in Experiments 1 and 3, blue dots in Experiment 2) appeared to be closer. The results indicated that both younger (mean age = 22 years) and older observers (mean age = 73 years) responded consistently with the ground dominance effect. However, the magnitude of the effect decreased for older observers. These results suggest a decreased use of ground surface information by older observers for the perceptual organization of scene layout. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Children's spatial analysis of hierarchical patterns: Construction and perception.

Two experiments were reported that aimed at investigating the development of spatial analysis of hierarchical patterns in children between 3 and 9 years of age. A total of 108 children participated in the drawing experiment, and 224 children were tested in a force-choice similarity judgment task. In both tasks, participants were exposed to consistent and inconsistent targets for short (300-ms) and long (3-s) durations. The drawing task showed that 3-year-old children either preferred to draw the local level or reproduced both levels in a nonintegrated manner. Coordination between the 2 processes started to emerge at 4 years of age, and 6-year-old children produced essentially correct integrated responses. The similarity judgment task confirmed that local processing dominated at 3 years of age. Preference for global processing appeared at 5 years of age, and it gained in strength later. Significant effects of stimulus consistency and stimulus duration were also found. In particular, the use of inconsistent patterns in the similarity judgment task revealed a phenomenon of local-to-global interference in the 3-year-olds. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

On the nature of global dominance in object perception.

Taken together, the previous studies confirm that global information is favoured during the processing of compound stimuli. In addition, global dominance occurs during both preattentive and attentive processing. The nature of this dominance is affected by whether or not an object is attended. Preattentive analysis leads to an automatic categorization but not to the identification of global features, whereas attentive processing lead to an inevitable identification of global information. Finally, the studies demonstrated a fundamental difference between global and local processing which seem to differ in their automatically level; local processing is greatly affected by attentional set, whereas global processing appears less subject to high level cognitive strategy. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Psychosexual conflicts and defenses in visual perception.

Tachistoscopically presented stimulus material (Blacky pictures) is used to study perceptual defense and vigilance in persons with different psychosexual conflict dimensions and ego-defense preferences. It is hypothesized that when stimulus material is presented below the threshold of conscious recognition, perceptually vigilant behavior will be evoked under conditions where ego-defense mechanisms are not likely to operate, and perceptually defensive behavior will be evoked where ego-defense mechanisms are likely to operate. The vigilance and defense hypotheses are confirmed by the results. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Aging and perception of visual form from temporal structure.

In this study, the authors examined age-related changes in participants' ability to perceive global spatial structure defined by temporal fine structure among elements undergoing rapid, irregular change. Participants were also tested on a task involving form recognition from luminance contrast and on a task dependent on perception of 3-dimensional shape from motion. Compared with young adults, older individuals were less sensitive to spatial form defined by temporal structure. In contrast, older observers performed as well as young adults on the other two tasks that were not dependent on temporal sensitivity, ruling out nonsensory factors as the cause of the deficits on the temporal structure task. This selective deficit may reveal reduced sensitivity within the temporal impulse response of the aging visual system, a deficit that could be related to reduced effectiveness of neural inhibition. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Hemiface contributions to hemispheric dominance in visual speech perception.

Lateralized displays are used widely to investigate hemispheric asymmetry in language perception. However, few studies have used lateralized displays to investigate hemispheric asymmetry in visual speech perception, and those that have yielded mixed results. This issue was investigated in the current study by presenting visual speech to either the left hemisphere (LH) or the right hemisphere (RH) using the face as recorded (normal), a mirror image of the normal face (reversed), and chimeric displays constructed by duplicating and reversing just one hemiface (left or right) to form symmetrical images (left-duplicated, right-duplicated). The projection of displays to each hemisphere was controlled precisely by an automated eye-tracking technique. Visual speech perception showed the same, clear LH advantage for normal and reversed displays, a greater LH advantage for right-duplicated displays, and no hemispheric difference for left-duplicated displays. Of particular note is that perception of LH displays was affected greatly by the presence of right-hemiface information, whereas perception of RH displays was unaffected by changes in hemiface content. Thus, when investigated under precise viewing conditions, the indications are not only that the dominant processes of visual speech perception are located in the LH but that these processes are uniquely sensitive to right-hemiface information. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Metrics of visual form.

A review of research work relating perceptual response to physical form parameters. The parameters are classified into transitive, transpositional, and intransitive. The number of intransitive parameters, which comprise measures that specify the characteristics of shape contours proper and contain the bulk of all physical measures, is quite large, but only very recent work has begun to point to the existence of a common denominator of these measures and to the possibility of arriving at a limited set of related and homogeneous parameters based on both empirical evidence and a priori mathematical considerations. (64 ref.) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Perceptual organization of moving stimuli modulates the flash-lag effect.

When a visual stimulus is flashed at a given location the moment a second moving stimulus arrives at the same location, observers report the flashed stimulus as spatially lagging behind the moving stimulus (the flash-lag effect). The authors investigated whether the global configuration (perceptual organization) of the moving stimulus influences the magnitude of the flash-lag effect. The results indicate that a flash presented near the leading portion of a moving stimulus lags significantly more than a flash presented near the trailing portion. This result also holds for objects consisting of several elements that group to form a unitary percept of an object in motion. The present study demonstrates a novel interaction between the global configuration of moving objects and the representation of their spatial position and may provide a new and useful tool for the study of perceptual organization. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Dominance as a factor in interpersonal choice and perception.

The hypotheses herein tested were that a person chooses to interact with, and tends to perceive other people in terms of the complement of his own degree of dominance. Ss were shown a movie depicting the interaction between 4 people, 2 of whom displayed dominant behavior, 2, submissive. Measures of the Ss' own dominance were compared with their answers on a sociometric questionnaire which elicited Ss' preference for the actors. The results failed to support the hypotheses as stated. The findings were discussed in terms of their possible meaning, and their relationship to other findings. 25 refs. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Encouraging the perceptual underdog: Positive affective priming of nonpreferred local–global processes.

Two experiments examined affective priming of global and local perception. Participants attempted to detect a target that might be present as either a global or a local shape. Verbal primes were used in 1 experiment, and pictorial primes were used in the other. In both experiments, positive primes led to improved performance on the nonpreferred dimension. For participants exhibiting global precedence, detection of local targets was significantly improved, whereas for participants exhibiting local precedence, detection of global targets was significantly improved. The results provide support for an interpretation of the effects of positive affective priming in terms of increased perceptual flexibility. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

The validity of hypnotically induced visual hallucinations.

Varying degrees of visual distortion were found to be related to varying degrees of hypnotic trance. In general, hypnotically induced perceptual distortion was not as effective as the "real thing." (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

What does visual agnosia tell us about perceptual organization and its relationship to object perception?

The authors studied 2 patients, S.M. and R.N., to examine perceptual organization and its relationship to object recognition. Both patients had normal, low-level vision and performed simple grouping operations normally but were unable to apprehend a multielement stimulus as a whole. R.N. failed to derive global structure even under optimal stimulus conditions, was less sensitive to grouping by closure, and was more impaired in object recognition than S.M. These findings suggest that perceptual organization involves a multiplicity of processes, some of which are simpler and are instantiated in lower order areas of visual cortex (e.g., collinearity). Other processes are more complex and rely on higher order visual areas (e.g., closure and shape formation). The failure to exploit these latter configural processes adversely affects object recognition. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Practise strengthens haptic capture.

When do haptic estimates of discordant visual-haptic size capture vision? Observers looked at a square through a minifying lens (50%) whilst they simultaneously touched the square from below through a hand-concealing cloth. Their subsequent match of the square’s size, rendered by touching a set of comparison squares, was haptically biased when they practised estimating the square’s size (Experiment 1, N = 72), when they actively explored rather than passively touched the square (Experiment 2, N = 24), but not when they were uninformed before inspecting the square that they would estimate its size (Experiment 3, N = 36). Evidently, the haptic exploratory strategies occasioned by the practise influenced the integration of the felt size and the seen size by weighing the haptic input more than the visual input, and this weight shifting manifested itself by strengthening haptic capture. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

High-level aftereffects to global scene properties.

Adaptation is ubiquitous in the human visual system, allowing recalibration to the statistical regularities of its input. Previous work has shown that global scene properties such as openness and mean depth are informative dimensions of natural scene variation useful for human and machine scene categorization (Greene & Oliva, 2009b; Oliva & Torralba, 2001). A visual system that rapidly categorizes scenes using such statistical regularities should be continuously updated, and therefore is prone to adaptation along these dimensions. Using a rapid serial visual presentation paradigm, we show aftereffects to several global scene properties (magnitude 8–21%). In addition, aftereffects were preserved when the test image was presented 10 degrees away from the adapted location, suggesting that the origin of these aftereffects is not solely due to low-level adaptation. We show systematic modulation of observers' basic-level scene categorization performances after adapting to a global property, suggesting a strong representational role of global properties in rapid scene categorization. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Perceptual load alters visual excitability.

Increasing perceptual load reduces the processing of visual stimuli outside the focus of attention, but the mechanism underlying these effects remains unclear. Here we tested an account attributing the effects of perceptual load to modulations of visual cortex excitability. In contrast to stimulus competition accounts, which propose that load should affect simultaneous, but not sequential, stimulus presentations, the visual excitability account makes the novel prediction that load should affect detection sensitivity for both simultaneous and sequential presentations. Participants fixated a stimulus stream, responding to targets defined by either a color (low load) or color and orientation conjunctions (high load). Additionally, detection sensitivity was measured for a peripheral critical stimulus (CS) presented occasionally. Increasing load at fixation reduced sensitivity to the peripheral CSs; this effect was similar regardless of whether CSs were presented simultaneously with central stimuli or during the (otherwise empty) interval between them. Controls ruled out explanations of the results in terms of strategic task prioritization. These findings support a cortical excitability account for perceptual load, challenging stimulus competition accounts. (PsycINFO Database Record (c) 2011 APA, all rights reserved)     

The serial process in visual search.

The conditions for serial search are described. A multiple target search methodology (Thornton & Gilden, 2007) is used to home in on the simplest target/distractor contrast that effectively mandates a serial scheduling of attentional resources. It is found that serial search is required when (a) targets and distractors are mirror twins, and (b) when the search elements lack the Gestalt property of intrinsic orientation. The finding is put into the context of Feature Integration Theory (Treisman & Gelade, 1980) that first identified the occasions of serial search to be important to object perception and understanding. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Infant sensitivity to trajectory forms.

The authors investigated whether infants are sensitive to visual event trajectory forms, and whether they are sensitive to the underlying dynamics of trajectory forms. The authors habituated 8-month-old infants to a videotaped event run either forward or reversed in time and then switched them to the same event run in the opposite direction. Infants dishabituated when switched to the event with the novel direction in time, indicating sensitivity to the form of the trajectory. Infants exhibited equivalent habituation rates and looking times for forward and reversed events, thus failing to provide evidence that infants are sensitive to the underlying dynamics. In a partial replication of this first experiment, the same pattern of results was found. Both experiments revealed infant sensitivity to the trajectory forms, but not the underlying dynamics of events. The authors discuss implications for methods used in infant event perception studies. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Aging and visual marking: Selective deficits for moving stimuli.

The selective processing of new visual information can be facilitated by the top-down inhibition of old stimuli already in the visual field, a capacity-limited process termed visual marking (D. G. Watson & G. W. Humphreys, 1997). Three experiments assessed the effects of aging on visual marking using stationary (Experiment 1) and moving (Experiments 2 and 3) items. For young participants, visual marking was observed in all experiments. For older participants, visual marking was observed only with stationary items. The results are not consistent with any simple account of general age-related decrements and provide further support for the deployment of different methods of visual marking depending on the properties of the old items and the current task demands. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Experimental investigations of the genesis of visual space perception.

The methodology and findings of 3 categories of experimental studies are reviewed and evaluated: (a) studies of organisms that have been deprived of visual stimulation until the time of testing, (b) studies of newborn organisms that are tested soon after birth, and (c) studies in which E controls the visual stimulation to which O is exposed from birth to the time of testing. The evidence provided by these experiments suggests that conclusions about the genetic basis of space perception will differ depending on the stimulus correlates under consideration.—(47 ref.) (PsycINFO Database Record (c) 2010 APA, all rights reserved)