Visual context integration is not fully developed in 4-year-old children

Long-range horizontal interactions supporting contour integration were found to be weaker in children than in adults (Kovács et al, 1999 Proceedings of the National Academy of Sciences of the USA 96 12204-12209). In the present study, integration on a larger scale, between a target and its context was investigated. Contextual modulation of the percept of a local target can be directly measured in the case of geometric illusions. We compared the magnitude of a size contrast illusion (Ebbinghaus illusion or Titchener circles) in children and adults. 4-year-old children and adults performed 2AFC size comparisons between two target disks in the classical Ebbinghaus illusion display and in two other modified versions. We found that the magnitude of the illusion effect was significantly smaller in children than in adults. Our interpretation is that context integration is not fully developed in 4-year-old children. Closer-to-veridical-size estimations by children demonstrate that the perception of the local target is less affected by stimulus context in their case. We suggest that immature cortical connectivity is behind the reduced contextual sensitivity in children.     

Size perception is less context-sensitive in males

Context sensitivity of size perception has previously been used to study individual differences related to the distinction between local, analytic, or field-independent and global, holistic, or field-dependent perceptual styles. For example, it has been used in several recent studies of autistic spectrum disorders, which may involve an excessive bias toward local processing. Autism is much more common in males, and there is evidence that this may be in part because males in general tend to be less context-sensitive than females, and thus are more affected by conditions that further reduce context sensitivity. There is also evidence that a bias to local processing is more common in professions that require attention to detail. Context sensitivity of size perception was therefore studied as a function of sex and academic discipline in sixty-four university staff and students by a simple, sensitive, and specific psychophysical measure based on the Ebbinghaus illusion. The results show that in this task males are on average less context-sensitive than females, that the overlap is large, and that subjects with very high or very low context sensitivity tend to have the sex and profession predicted by the above hypotheses.     

Perception of the Ebbinghaus illusion in 5- to 8-month-old infants

The Ebbinghaus illusion is a geometric illusion based on a size-contrast between a central circle and surrounding circles. A central circle surrounded by small inducing circles is perceived as being larger than a central circle surrounded by large inducing circles. In the present study we investigated 5- to 8-month-old infants' perception of the Ebbinghaus illusion using a preferential-looking paradigm. We measured the preference between a central circle surrounded by small inducing circles (overestimated figure) and a central circle surrounded by large inducing circles (underestimated figure). Infants showed a significant preference for the overestimated figure when the central circle was flashing, but not when it was static. Furthermore, there was no preference between the two figures when the central circles were removed. These results suggest that infants' preference reflects their perception of the size illusion of the central circle. There is a possibility that 5- to 8-month-old infants perceive the Ebbinghaus illusion.     

Yang's iris illusion: External contour causes length‐assimilation illusions1

The Delboeuf illusion and the Ebbinghaus illusion (also known as the Titchener illusion) demonstrate that an external contour can lead to size‐assimilation and size‐contrast perception. This paper explores a novel illusion, revealing that neighboring external contours can also lead to a distortion in length perception. The illusion was originally discovered from a face stimulus (Experiment 1) in which a face was depicted alongside its mirror image so as to make the four irises absolutely equidistant. The distance between the middle two irises was underestimated in Asian faces, but overestimated in Caucasian faces. The illusion was also maintained when the facial stimuli were replaced by line drawings of eyes (Experiment 2). However, the illusion vanished when the irises were presented alone. Further scrutiny of the differences in facial characteristics between Asian and Caucasian faces reveals that the illusion might be elicited by the relative position of the eye shapes. This hypothesis was confirmed in Experiment 3, in which the distances between the eye shapes and the irises were manipulated.     

The Ebbinghaus illusion modulates visual search for size-defined targets: evidence for preattentive processing of apparent object size

Five search experiments investigated whether the apparent size of objects is, like their retinal size, coded in preattentive vision. Observers searched for a target circle that was either larger or smaller than distractor circles, with both types of test circles surrounded by context circles modulating apparent size (i.e., the Ebbinghaus illusion). The size ratio between the test and the context circles was manipulated in such a way that the test circles were surrounded by, for example, smaller context circles (making the larger target appear even larger) or by larger context circles (making the smaller distractors appear even smaller). Under optimal conditions, the detection reaction times were independent of the number of test circles in the display, and the Ebbinghaus illusion facilitated the detection of the target even in comparison with control conditions without any context circles. This finding is consistent with preattentive, spatially parallel processing of apparent size.     

More accurate size contrast judgments in the Ebbinghaus Illusion by a remote culture

The Ebbinghaus (Titchener) illusion was examined in a remote culture (Himba) with no words for geometric shapes. The illusion was experienced less strongly by Himba compared with English participants, leading to more accurate size contrast judgments in the Himba. The study included two conditions of inducing stimuli. The illusion was weaker when the inducing stimuli were dissimilar (diamonds) to the target (circle) compared with when they were similar (circles). However, the illusion was weakened to the same extent in both cultures. It is argued that the more accurate size judgments of the Himba derive from their tendency to prioritize the analysis of local details in visual processing of multiple objects, and not from their impoverished naming.     

Processing of audiovisually congruent and incongruent speech in school‐age children with a history of specific language impairment: a behavioral and event‐related potentials study

Previous studies indicate that at least some aspects of audiovisual speech perception are impaired in children with specific language impairment (SLI). However, whether audiovisual processing difficulties are also present in older children with a history of this disorder is unknown. By combining electrophysiological and behavioral measures, we examined perception of both audiovisually congruent and audiovisually incongruent speech in school‐age children with a history of SLI (H‐SLI), their typically developing (TD) peers, and adults. In the first experiment, all participants watched videos of a talker articulating syllables ‘ba’, ‘da’, and ‘ga’ under three conditions – audiovisual (AV), auditory only (A), and visual only (V). The amplitude of the N1 (but not of the P2) event‐related component elicited in the AV condition was significantly reduced compared to the N1 amplitude measured from the sum of the A and V conditions in all groups of participants. Because N1 attenuation to AV speech is thought to index the degree to which facial movements predict the onset of the auditory signal, our findings suggest that this aspect of audiovisual speech perception is mature by mid‐childhood and is normal in the H‐SLI children. In the second experiment, participants watched videos of audivisually incongruent syllables created to elicit the so‐called McGurk illusion (with an auditory ‘pa’ dubbed onto a visual articulation of ‘ka’, and the expectant perception being that of ‘ta’ if audiovisual integration took place). As a group, H‐SLI children were significantly more likely than either TD children or adults to hear the McGurk syllable as ‘pa’ (in agreement with its auditory component) than as ‘ka’ (in agreement with its visual component), suggesting that susceptibility to the McGurk illusion is reduced in at least some children with a history of SLI. Taken together, the results of the two experiments argue against global audiovisual integration impairment in children with a history of SLI and suggest that, when present, audiovisual integration difficulties in this population likely stem from a later (non‐sensory) stage of processing.     

Geometrical haptic illusions: The role of exploration in the Müller-Lyer,vertical-horizontal,and Delboeuf illusions

This article surveys studies of the occurrence, in the haptic modality, of three geometrical illusions well known in vision, and it discusses the nature of the processes underlying these haptic illusions.We argue that the apparently contradictory results found in the literature concerning them may be explained, at least partially, by the characteristics of manual exploratory movements. The Müller-Lyer illusion is present in vision and in haptics and seems to be the result of similar processes in the two modalities. The vertical-horizontal illusion also exists in vision and haptics but is due partly to similar processes (bisection) and partly to processes specific to each modality (anisotropy of the visual field and overestimation of radial vs. tangential manual exploratory movements). The Delboeuf illusion seems to occur only in vision, probably because exploration by the index finger may exclude the misleading context from tactile perception. The role of these haptic exploratory movements may explain why haptics is as sensitive as vision to certain illusions and less sensitive to others.     

Perception of the Ebbinghaus illusion in four-day-old domestic chicks (Gallus gallus)

In the Ebbinghaus size illusion, a central circle surrounded by small circles (inducers) appears bigger than an identical one surrounded by large inducers. Previous studies have failed to demonstrate sensitivity to this illusion in pigeons and baboons, leading to the conclusion that avian species (possibly also nonhuman primates) might lack the neural substrate necessary to perceive the Ebbinghaus illusion in a human-like fashion. Such a substrate may have been only recently evolved in the primate lineage. Here, we show that this illusion is perceived by 4-day-old domestic chicks. During rearing, chicks learnt, according to an observational-learning paradigm, to find food in proximity either of a big or of a small circle. Subjects were then tested with Ebbinghaus stimuli: two identical circles, one surrounded by larger and the other by smaller inducers. The percentage of approaches to the perceptually bigger target in animals reinforced on the bigger circle (and vice versa for the other group) was computed. Over four experiments, we demonstrated that chicks are reliably affected by the illusory display. Subjects reinforced on the small target choose the configuration with big inducers, in which the central target appears perceptually smaller; the opposite is true for subjects reinforced on the big target. This result has important implications for the evolutionary history of the neural substrate involved in the perception of the Ebbinghaus illusion.     

Mental reinstatement of the misinformation context and the misinformation effect in children and adults

The present study investigated the effects of mental reinstatement of the context in which misleading information about an event was presented on later recognition memory for the event. Five‐year‐olds, 7‐year‐olds and adults were shown a short video depicting a children's adventure and were asked a set of misleading questions to introduce misinformation one week later. Before the recognition memory test was administered another week later, half of the participants were given instructions to mentally reinstate the context of the misleading interview. Memory was assessed with a set of forced‐choice recognition questions once in the misleading interview context and for the children a second time at home one week later. When participants were instructed to mentally reinstate the context of the misleading interview prior to the recognition test, false memory reports occurred more often for adults than for children and had a stronger impact on peripheral information than on central information for both 7‐year‐olds and adults. When 5‐ and 7‐year‐olds were tested at home, false memory reports decreased. Thus, reinstating the context of an interview introducing misinformation can reduce the accuracy of memory reports; the context dependence of both accurate and inaccurate memory reports in children and adults is discussed. Copyright © 2003 John Wiley & Sons, Ltd.     

Outgroup homogeneity effect in perception: An exploration with Ebbinghaus illusion

An outgroup homogeneity (OH) effect implies that outgroup members are perceived to be more similar than ingroup members. At present, however, it is not clear whether the OH effect is truly perceptual. Here, we used an Ebbinghaus illusion to demonstrate the OH effect in perception. Participants were presented with one central face that was surrounded by four surrounding faces. The central face was judged to be smaller as the size of the surrounding faces increased, thereby demonstrating an Ebbinghaus illusion. As predicted, however, this illusion was significantly greater when the faces allegedly belonged to an outgroup than when they allegedly belonged to an ingroup. This perceptual OH effect bore no significant relationship with cognitive OH measures. The perceptual versus cognitive OH effects might therefore be mediated by separate mechanisms.     

Attenuation of size illusion effect in dual-task conditions

We over-estimate or under-estimate the size of an object depending its background structure (e.g., the Ebbinghaus illusion). Since deciding and preparing to execute a movement is based on perception, motor performance deteriorates due to the faulty perception of information. Therefore, such cognitive process can be a source of a failure in motor performance, although we feel in control of our performance through conscious cognitive activities. If a movement execution process can avoid distraction by the illusion-deceived conscious process, the effect of the visual illusion on visuomotor performance can be eliminated or attenuated. This study investigated this hypothesis by examining two task performances developed for a target figure inducing the Ebbinghaus size illusion: showing visually perceived size of an object by index finger-thumb aperture (size-matching), and reaching out for the object and pretending to grasp it (pantomimed grasping). In these task performances, the size of the index finger-thumb aperture becomes larger or smaller than the actual size, in accordance with the illusion effect. This study examined whether the size illusion effect can be weakened or eliminated by the dual-task condition where actors’ attention to judge the object’s size and to produce the aperture size is interrupted. 16 participants performed the size-matching and pantomimed grasping tasks while simultaneously executing a choice reaction task (dual task) or without doing so (single task). Using an optical motion capture system, the size-illusion effect was analyzed in terms of the aperture size, which indicates the visually perceived object size. The illusion effect was attenuated in the dual task condition, compared to it in the single task condition. This suggests that the dual task condition modulated attention focus on the aperture movement and therefore the aperture movement was achieved with less distraction caused by illusory information.     

Visual context processing and its development in gamers and non-gamers

Visual context processing was investigated in both action video game players and nonplayers using the Ebbinghaus illusion task (N = 312, 39.4% female) in a cross-sectional study design. When presented in context, players showed markedly poorer target size discrimination accuracy compared with nonplayers in the 6-, 7-, 8-, and 9-years old age groups, but this difference was reduced in 10-years old group and diminished in adults. When presented in isolation (no-context), the two groups displayed similar performance in all age groups. Furthermore, nonplayers (linear) and players (bell curve) showed profoundly different age-related differences in context processing. These findings provide evidence that players might have enhanced perceptual bias to process visual context in the transition from early childhood to early adolescence, and the differences between the two groups start at early ages and continue with distinct developmental profiles.     

Grasping visual illusions: no evidence for a dissociation between perception and action

Neuropsychological studies prompted the theory that the primate visual system might be organized into two parallel pathways, one for conscious perception and one for guiding action. Supporting evidence in healthy subjects seemed to come from a dissociation in visual illusions: In previous studies, the Ebbinghaus (or Titchener) illusion deceived perceptual judgments of size, but only marginally influenced the size estimates used in grasping. Contrary to those results, the findings from the present study show that there is no difference in the sizes of the perceptual and grasp illusions if the perceptual and grasping tasks are appropriately matched. We show that the differences found previously can be accounted for by a hitherto unknown, nonadditive effect in the illusion. We conclude that the illusion does not provide evidence for the existence of two distinct pathways for perception and action in the visual system.     

Making features similar: comparison processes affect perception

In this paper, the constructive nature of comparison processes (both similarity- and differenceoriented judgments) is examined through their effects on visual perception. Previous research has shown that comparison processes enhance the tendency to interpret ambiguous objects in the light of the unambiguous objects with which they are compared (Medin, Goldstone, & Gentner, 1993). In the present paper, it is argued that comparison processes affect not only the interpretation of objects, but also their perception. In addition, it is argued that the perceptual effects of similarity-oriented comparison processes differ from those of difference-oriented comparison processes. Accordingly, it is demonstrated that when estimation of an object’s size is preceded by similarity-oriented comparisons, the Ebbinghaus illusion practically disappears, whereas prior difference-oriented comparisons tend to enhance the illusion.     

Seeing the body distorts tactile size perception

Vision of the body modulates somatosensation, even when entirely non-informative about stimulation. For example, seeing the body increases tactile spatial acuity, but reduces acute pain. While previous results demonstrate that vision of the body modulates somatosensory sensitivity, it is unknown whether vision also affects metric properties of touch, and if so how. This study investigated how non-informative vision of the body modulates tactile size perception. We used the mirror box illusion to induce the illusion that participants were directly seeing their stimulated left hand, though they actually saw their reflected right hand. We manipulated whether participants: (a) had the illusion of directly seeing their stimulated left hand, (b) had the illusion of seeing a non-body object at the same location, or (c) looked directly at their non-stimulated right-hand. Participants made verbal estimates of the perceived distance between two tactile stimuli presented simultaneously to the dorsum of the left hand, either 20, 30, or 40 mm apart. Vision of the body significantly reduced the perceived size of touch, compared to vision of the object or of the contralateral hand. In contrast, no apparent changes of perceived hand size were found. These results show that seeing the body distorts tactile size perception.     

Computation of mean size is based on perceived size

The present study investigated whether computation of mean object size was based on perceived or physical size. The Ebbinghaus illusion was used to make the perceived size of a circle different from its physical size. Four Ebbinghaus configurations were presented either simultaneously (Experiment 1) or sequentially (Experiment 2) to each visual field, and participants were instructed to attend only to the central circles of each configuration. Participants’ judgments of mean central circle size were influenced by the Ebbinghaus illusion. In addition, the Ebbinghaus illusion influenced the coding of individual size rather than the averaging. These results suggest that perceived rather than physical size was used in computing the mean size.     

Comparison of grouping abilities in humans (Homo sapiens) and baboons (Papio papio) with the Ebbinghaus illusion

This research comparatively assessed grouping mechanisms of humans (n = 8) and baboons (n = 8) in an illusory task that employs configurations of target and surrounding circles arranged to induce the Ebbinghaus (Titchener) illusion. Analyses of response behaviors and points of subjective equality demonstrated that only humans misjudged the central target size under the influence of the Ebbinghaus illusion, whereas baboons expressed a more veridical perception of target sizes. It is argued that humans adopted a global mode of stimulus processing of the illusory figure in our task that has favored the illusion. By contrast, a strong local mode of stimulus processing with attention restricted to the target must have prevented illusory effects in baboons. These findings suggest that monkeys and humans have evolved modes of object recognition that do not similarly rely on the same gestalt principles.     

Fearful faces drive gaze‐cueing and threat bias effects in children on the lookout for danger

Most developmental studies of face emotion processing show faces in isolation, in the absence of any broader context. Here we investigate two types of interactions between expression and threat contexts. First, in adults, following of another person's direction of social attention is increased when that person shows fear and the context requires vigilance for danger. We investigate whether this also occurs in children. Using a Posner‐style eye‐gaze cueing paradigm, we tested whether children would show greater gaze‐cueing from fearful than happy expressions when the task was to be vigilant for possible dangerous animals. Testing across the 8–12‐year‐old age range, we found this fear priority effect was absent in the youngest children but developed to reach adult levels in the oldest children. However, even the oldest children were unable to sustain fear‐prioritization when the onset of the target was delayed. Second, we addressed the development of ‘threat bias’ – namely faster identification of dangerous animals than safe animals – in the social context provided by expressive faces. In our non‐anxious samples (i.e. with typical‐population levels of anxiety), adults showed a threat bias regardless of the expression or looking direction of the just‐seen cue face whereas 8–12‐year‐olds only showed a threat bias when the just‐seen cue face displayed fear. Overall, the results argue that some, but not all, aspects of expression–context interactions are mature by 12 years of age.     

Children's sensitivity to traffic hazard in peripheral vision

Although children and adults have poorer peripheral vision than foveal vision there is contradictory evidence about the developmental changes that occur in peripheral sensitivity. Previous research on detections of traffic hazard has not, however, provided any evidence that peripheral vision is implicated in the particualr vulnerability of children to pedestrain accidents. In the absence of differences in peripheral detections it was hypothesized that children may nevertheless be less efficient than adults in utilizing information presented in the periphery. Road traffic scenes depicting vehicles in potentially hazardous and non-hazardous positions for road crossings were presented to adults and to childre, aged 7, 9, and 11. Results confirmed that children were relatively no poorer than adults at hazard detection in peripheral vision than in foveal vision, but indicated that they were marginally poorer at utilizing information presented in the periphery, as measured by a vehicle recognition test. Against expectd developmental trends 9-year-olds were as fast as adults at hazard detection, but no different from the other groups of children in recognition performance. Evidence that information detected and assimilated in peripheral vision does not contribute to the high pedestrian accident rates of children comes from the absence of any sex differences favouring girls. Since girls have considerably lower accident rates than boys, it would have been expected that both their detection and recognition performance would have been higher.