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Drissi H, Jurkiewicz T, Vialatte A, Khan AZ, Pisella L. Impact of macular scotoma and tubular vision on oculomotor behavior and performance in visuospatial comparison tasks. J Vis 2024; 24:2. [PMID: 39226068 PMCID: PMC11373732 DOI: 10.1167/jov.24.9.2] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 09/04/2024] Open
Abstract
Our aim in this study was to understand how we perform visuospatial comparison tasks by analyzing ocular behavior and to examine how restrictions in macular or peripheral vision disturb ocular behavior and task performance. Two groups of 18 healthy participants with normal or corrected visual acuity performed visuospatial comparison tasks (computerized version of the elementary visuospatial perception [EVSP] test) (Pisella et al., 2013) with a gaze-contingent mask simulating either tubular vision (first group) or macular scotoma (second group). After these simulations of pathological conditions, all participants also performed the EVSP test in full view, enabling direct comparison of their oculomotor behavior and performance. In terms of oculomotor behavior, compared with the full view condition, alternation saccades between the two objects to compare were less numerous in the absence of peripheral vision, whereas the number of within-object exploration saccades decreased in the absence of macular vision. The absence of peripheral vision did not affect accuracy except for midline judgments, but the absence of central vision impaired accuracy across all visuospatial subtests. Besides confirming the crucial role of the macula for visuospatial comparison tasks, these experiments provided important insights into how sensory disorder modifies oculomotor behavior with or without consequences on performance accuracy.
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Affiliation(s)
- Hind Drissi
- Centre de Recherche en Neurosciences de Lyon (CRNL), Université Claude Bernard Lyon 1, INSERM U1028, Bron, France
| | - Tristan Jurkiewicz
- Centre de Recherche en Neurosciences de Lyon (CRNL), Université Claude Bernard Lyon 1, INSERM U1028, Bron, France
| | - Audrey Vialatte
- Centre de Recherche en Neurosciences de Lyon (CRNL), Université Claude Bernard Lyon 1, INSERM U1028, Bron, France
| | | | - Laure Pisella
- Centre de Recherche en Neurosciences de Lyon (CRNL), Université Claude Bernard Lyon 1, INSERM U1028, Bron, France
- https://orcid.org/0000-0001-6550-3774
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2
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Luo ZX, Pan WN, Zeng XJ, Gong LY, Cai YC. Endogenous attention enhances contrast appearance regardless of stimulus contrast. Atten Percept Psychophys 2024:10.3758/s13414-024-02929-z. [PMID: 38992320 DOI: 10.3758/s13414-024-02929-z] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 06/24/2024] [Indexed: 07/13/2024]
Abstract
There has been enduring debate on how attention alters contrast appearance. Recent research indicates that exogenous attention enhances contrast appearance for low-contrast stimuli but attenuates it for high-contrast stimuli. Similarly, one study has demonstrated that endogenous attention heightens perceived contrast for low-contrast stimuli, yet none have explored its impact on high-contrast stimuli. In this study, we investigated how endogenous attention alters contrast appearance, with a specific focus on high-contrast stimuli. In Experiment 1, we utilized the rapid serial visual presentation (RSVP) paradigm to direct endogenous attention, revealing that contrast appearance was enhanced for both low- and high-contrast stimuli. To eliminate potential influences from the confined attention field in the RSVP paradigm, Experiment 2 adopted the letter identification paradigm, deploying attention across a broader visual field. Results consistently indicated that endogenous attention increased perceived contrast for high-contrast stimuli. Experiment 3 employed equiluminant chromatic letters as stimuli in the letter identification task to eliminate potential interference from contrast adaption, which might have occurred in Experiment 2. Remarkably, the boosting effect of endogenous attention persisted. Combining the results from these experiments, we propose that endogenous attention consistently enhances contrast appearance, irrespective of stimulus contrast levels. This stands in contrast to the effects of exogenous attention, suggesting that mechanisms through which endogenous attention alters contrast appearance may differ from those of exogenous attention.
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Affiliation(s)
- Zi-Xi Luo
- Department of Psychology and Behavioral Sciences, Zhejiang University (Zijingang Campus), Yuhangtang Road No. 866, Zhejiang Province, 310058, People's Republic of China
| | - Wang-Nan Pan
- Department of Psychology and Behavioral Sciences, Zhejiang University (Zijingang Campus), Yuhangtang Road No. 866, Zhejiang Province, 310058, People's Republic of China
| | - Xiang-Jun Zeng
- Department of Psychology and Behavioral Sciences, Zhejiang University (Zijingang Campus), Yuhangtang Road No. 866, Zhejiang Province, 310058, People's Republic of China
| | - Liang-Yu Gong
- Department of Psychology and Behavioral Sciences, Zhejiang University (Zijingang Campus), Yuhangtang Road No. 866, Zhejiang Province, 310058, People's Republic of China
| | - Yong-Chun Cai
- Department of Psychology and Behavioral Sciences, Zhejiang University (Zijingang Campus), Yuhangtang Road No. 866, Zhejiang Province, 310058, People's Republic of China.
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3
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Chen L, Wu B, Yu H, Sperandio I. Network dynamics underlying alterations in apparent object size. Brain Commun 2024; 6:fcae006. [PMID: 38250057 PMCID: PMC10799746 DOI: 10.1093/braincomms/fcae006] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/21/2023] [Revised: 12/14/2023] [Accepted: 01/09/2024] [Indexed: 01/23/2024] Open
Abstract
A target circle surrounded by small circles looks larger than an identical circle surrounded by large circles (termed as the Ebbinghaus illusion). While previous research has shown that both early and high-level visual regions are involved in the generation of the illusion, it remains unclear how these regions work together to modulate the illusion effect. Here, we used functional MRI and dynamic causal modelling to investigate the neural networks underlying the illusion in conditions where the focus of attention was manipulated via participants directing their attention to and maintain fixation on only one of the two illusory configurations at a time. Behavioural findings confirmed the presence of the illusion. Accordingly, functional MRI activity in the extrastriate cortex accounted for the illusory effects: apparently larger circles elicited greater activation than apparently smaller circles. Interestingly, this spread of activity for size overestimation was accompanied by a decrease in the inhibitory self-connection in the extrastriate region, and an increase in the feedback connectivity from the precuneus to the extrastriate region. These findings demonstrate that the representation of apparent object size relies on feedback projections from higher- to lower-level visual areas, highlighting the crucial role of top-down signals in conscious visual perception.
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Affiliation(s)
- Lihong Chen
- Research Center of Brain and Cognitive Neuroscience, Liaoning Normal University, Dalian 116029, China
- Key Laboratory of Brain and Cognitive Neuroscience, Dalian 116029, Liaoning Province, China
| | - Baoyu Wu
- Research Center of Brain and Cognitive Neuroscience, Liaoning Normal University, Dalian 116029, China
- Key Laboratory of Brain and Cognitive Neuroscience, Dalian 116029, Liaoning Province, China
- Department of Psychology and Behavioral Sciences, Zhejiang University, Hangzhou 310058, China
| | - Haoyang Yu
- Research Center of Brain and Cognitive Neuroscience, Liaoning Normal University, Dalian 116029, China
- Key Laboratory of Brain and Cognitive Neuroscience, Dalian 116029, Liaoning Province, China
| | - Irene Sperandio
- Department of Psychology and Cognitive Science, University of Trento, Rovereto 38068, Italy
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4
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Kirsch W, Kunde W. On the origin of the Helmholtz's square illusion: An attentional account. Atten Percept Psychophys 2023; 85:2018-2032. [PMID: 37157009 PMCID: PMC10545586 DOI: 10.3758/s13414-023-02717-1] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 04/19/2023] [Indexed: 05/10/2023]
Abstract
A square filled with parallel horizontal or vertical lines appears perceptually extended in the direction orthogonal to the lines. Here, we suggest that this Helmholtz illusion arises due to changes in spatial attention that entail changes at very early stages of perceptual processing. Three experiments are reported which tested this assumption. In Experiment1 and Experiment2, transient attentional cues were flashed in such a way that they either promoted (congruent condition) or hindered (incongruent condition) the attentional state presumably induced by the target objects. We predicted a decline of the illusion in the incongruent condition compared with the congruent condition. This prediction was confirmed in both experiments. However, the influence of (in)congruent attention cuing on the Helmholtz illusion depended on more sustained distributions of attention as well. An influence of sustained attention on the illusion was confirmed in Experiment 3, in which changes of attentional focus were induced by a secondary task. Overall, the results were consistent with our claim that the origin of the Helmholtz illusion is closely linked to the distribution of spatial attention.
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Affiliation(s)
- Wladimir Kirsch
- Institut für Psychologie III der Universität Würzburg, Röntgenring 11, D-97070, Würzburg, Germany.
| | - Wilfried Kunde
- Institut für Psychologie III der Universität Würzburg, Röntgenring 11, D-97070, Würzburg, Germany
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5
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Urale PWB, Schwarzkopf DS. Effects of cortical distance on the Ebbinghaus and Delboeuf illusions. Perception 2023:3010066231175014. [PMID: 37335155 DOI: 10.1177/03010066231175014] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/21/2023]
Abstract
The Ebbinghaus and Delboeuf illusions affect the perceived size of a target circle depending on the size and proximity of circular inducers or a ring. Converging evidence suggests that these illusions are driven by interactions between contours mediated by their cortical distance in primary visual cortex. We tested the effect of cortical distance on these illusions using two methods: First, we manipulated retinal distance between target and inducers in a two-interval forced choice design, finding that targets appeared larger with a closer surround. Next, we predicted that targets presented peripherally should appear larger due to cortical magnification. Hence, we tested the illusion strength when positioning the stimuli at various eccentricities, with results supporting this hypothesis. We calculated estimated cortical distances between illusion elements in each experiment and used these estimates to compare the relationship between cortical distance and illusion strength across our experiments. In a final experiment, we modified the Delboeuf illusion to test whether the influence of the inducers/annuli in this illusion is influenced by an inhibitory surround. We found evidence that an additional outer ring makes targets appear smaller compared to a single-ring condition, suggesting that near and distal contours have antagonistic effects on perceived target size.
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Affiliation(s)
- Poutasi W B Urale
- School of Optometry & Vision Science, The University of Auckland, New Zealand
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6
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Wu X, Zhang T, Wang A, Zhang M. Different gain modulations of selective attention at short and long cue-target delays. Scand J Psychol 2023. [PMID: 36786056 DOI: 10.1111/sjop.12899] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/24/2022] [Revised: 12/08/2022] [Accepted: 01/02/2023] [Indexed: 02/15/2023]
Abstract
Previous studies have tested attentional gain patterns, for example, within the normalization model of attention (NMoA), by altering the relative sizes of the attention field and stimuli. Existing studies have not investigated whether the gain patterns of altering the relative exogenous cue size as compared with the target stimuli matches the prediction of NMoA and whether these gain patterns exist in the late stage of attentional processing. To resolve these questions, the present study maintained the target grating size and changed the exogenous cue size in both short and long cue-target onset asynchronies (CTOAs) conditions. The results revealed response gain for small cue/large target size conditions and contrast gain for large cue/small target size conditions, which was consistent with the NMoA. However, we observed the decrease in the contrast gain factor only with long CTOAs, regardless of whether the cue size was relatively small or large. This indicated that NMoA-related effects based on the relative attentional field dominated in the early stage and that the contrast gain dominated in the late stage.
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Affiliation(s)
- Xiaogang Wu
- Department of Psychology, Suzhou University of Science and Technology, Suzhou, China
| | - Tianyang Zhang
- Medical College of Soochow University, School of Public Health, Suzhou, China
| | - Aijun Wang
- Department of Psychology, Research Center for Psychology and Behavioral Sciences, Suzhou, China
| | - Ming Zhang
- Department of Psychology, Suzhou University of Science and Technology, Suzhou, China
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7
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Wu X, Liu M, Wang A, Zhang M. Different attentional focus sizes modulate the size-eccentricity effect. Psych J 2023; 12:25-33. [PMID: 36167945 DOI: 10.1002/pchj.604] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/27/2021] [Accepted: 08/16/2022] [Indexed: 02/04/2023]
Abstract
The size-eccentricity effect is a perceptual distortion phenomenon in which a peripherally located object is perceived to be smaller than a centrally located object. Although the increase in apparent object size caused by attention has been documented, little is known about the effect of different sizes of attentional focus on object appearance. The present study investigated how different sizes of attentional focus affect the size-eccentricity effect using a spatial pre-cueing paradigm. Additionally, we examined the influence of different task types on size perception. A peripheral object following a small attentional focus appeared larger, without observation of the size-eccentricity effect. In contrast, a peripheral object appeared smaller following a large attentional focus in both larger and smaller judgement tasks. These results suggest that the relative size of the attentional focus has opposite effects on the perception of object size, independent of task type. Furthermore, in addition to the structural properties of the retina and the locus of attention, the size of attentional focus determines the extent to which an object appears smaller in the periphery. The present study complements the attentional attraction field model of the size and density of population receptive fields in V1 and further explains how the effect of attention is restricted by retinal structure.
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Affiliation(s)
- Xiaogang Wu
- Department of Psychology, Suzhou University of Science and Technology, Suzhou, China
| | - Mingyuan Liu
- Department of Psychology, Research Center for Psychology and Behavioral Sciences, Soochow University, Suzhou, China
| | - Aijun Wang
- Department of Psychology, Research Center for Psychology and Behavioral Sciences, Soochow University, Suzhou, China
| | - Ming Zhang
- Department of Psychology, Suzhou University of Science and Technology, Suzhou, China
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8
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Tamè L, Limbu S, Harlow R, Parikh M, Longo MR. Size Constancy Mechanisms: Empirical Evidence from Touch. Vision (Basel) 2022; 6:vision6030040. [PMID: 35893757 PMCID: PMC9326730 DOI: 10.3390/vision6030040] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/01/2022] [Revised: 06/10/2022] [Accepted: 06/14/2022] [Indexed: 11/30/2022] Open
Abstract
Several studies have shown the presence of large anisotropies for tactile distance perception across several parts of the body. The tactile distance between two touches on the dorsum of the hand is perceived as larger when they are oriented mediolaterally (across the hand) than proximodistally (along the hand). This effect can be partially explained by the characteristics of primary somatosensory cortex representations. However, this phenomenon is significantly attenuated relative to differences in acuity and cortical magnification, suggesting a process of tactile size constancy. It is unknown whether the same kind of compensation also takes place when estimating the size of a continuous object. Here, we investigate whether the tactile anisotropy that typically emerges when participants have to estimate the distance between two touches is also present when a continuous object touches the skin and participants have to estimate its size. In separate blocks, participants judged which of two tactile distances or objects on the dorsum of their hand felt larger. One stimulation (first or second) was aligned with the proximodistal axis (along the hand) and the other with the mediolateral axis (across the hand). Results showed a clear anisotropy for distances between two distinct points, with across distances consistently perceived as larger than along distances, as in previous studies. Critically, however, this bias was significantly reduced or absent for judgments of the length of continuous objects. These results suggest that a tactile size constancy process is more effective when the tactile size of an object has to be approximated compared to when the distance between two touches has to be determined. The possible mechanism subserving these results is described and discussed. We suggest that a lateral inhibition mechanism, when an object touches the skin, provides information through the distribution of the inhibitory subfields of the RF about the shape of the tactile RF itself. Such a process allows an effective tactile size compensatory mechanism where a good match between the physical and perceptual dimensions of the object is achieved.
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Affiliation(s)
- Luigi Tamè
- School of Psychology, University of Kent, Canterbury CT2 7NP, UK
- Department of Psychological Sciences, Birkbeck, University of London, London WC1E 7HX, UK; (S.L.); (R.H.); (M.P.)
- Correspondence: (L.T.); (M.R.L.)
| | - Suzuki Limbu
- Department of Psychological Sciences, Birkbeck, University of London, London WC1E 7HX, UK; (S.L.); (R.H.); (M.P.)
| | - Rebecca Harlow
- Department of Psychological Sciences, Birkbeck, University of London, London WC1E 7HX, UK; (S.L.); (R.H.); (M.P.)
| | - Mita Parikh
- Department of Psychological Sciences, Birkbeck, University of London, London WC1E 7HX, UK; (S.L.); (R.H.); (M.P.)
| | - Matthew R. Longo
- Department of Psychological Sciences, Birkbeck, University of London, London WC1E 7HX, UK; (S.L.); (R.H.); (M.P.)
- Correspondence: (L.T.); (M.R.L.)
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9
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Jurkiewicz T, Salemme R, Froment C, Pisella L. Role of the Dorsal Posterior Parietal Cortex in the Accurate Perception of Object Magnitude in Peripheral Vision. Iperception 2021; 12:20416695211058476. [PMID: 34900214 PMCID: PMC8652191 DOI: 10.1177/20416695211058476] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/11/2021] [Accepted: 10/21/2021] [Indexed: 12/03/2022] Open
Abstract
Following superior parietal lobule and intraparietal sulcus (SPL-IPS) damage, optic ataxia patients underestimate the distance of objects in the ataxic visual field such that they produce hypometric pointing errors. The metrics of these pointing errors relative to visual target eccentricity fit the cortical magnification of central vision. The SPL-IPS would therefore implement an active “peripheral magnification” to match the real metrics of the environment for accurate action. We further hypothesized that this active compensation of the central magnification by the SPL-IPS contributes to actual object’ size perception in peripheral vision. Three optic ataxia patients and 10 age-matched controls were assessed in comparing the thickness of two rectangles flashed simultaneously, one in central and another in peripheral vision. The bilateral optic ataxia patient exhibited exaggerated underestimation bias and uncertainty compared to the control group in both visual fields. The two unilateral optic ataxia patients exhibited a pathological asymmetry between visual fields: size perception performance was affected in their contralesional peripheral visual field compared to their healthy side. These results demonstrate that the SPL-IPS contributes to accurate size perception in peripheral vision.
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Affiliation(s)
- Tristan Jurkiewicz
- Centre de Recherche en Neurosciences de Lyon (CRNL), Université de Lyon, Bron, France
| | - Romeo Salemme
- Centre de Recherche en Neurosciences de Lyon (CRNL), Université de Lyon, Bron, France
| | - Caroline Froment
- Centre de Recherche en Neurosciences de Lyon (CRNL), Université de Lyon, Bron, France
| | - Laure Pisella
- Centre de Recherche en Neurosciences de Lyon (CRNL), Université de Lyon, Bron, France
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10
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Han Y, Tan Z, Zhuang H, Qian J. Contrasting effects of exogenous and endogenous attention on size perception. BRITISH JOURNAL OF PSYCHOLOGY (LONDON, ENGLAND : 1953) 2021; 113:153-175. [PMID: 34435351 DOI: 10.1111/bjop.12529] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Subscribe] [Scholar Register] [Received: 02/01/2021] [Accepted: 08/16/2021] [Indexed: 11/30/2022]
Abstract
Although neuroimaging studies have shown that exogenous and endogenous attention are dissociable, only a few behavioural studies have explored their differential effects on visual sensitivity, and none have directly focused on visual appearance. Here, we show that exogenous and endogenous attention produces contrasting effects on apparent size. Participants performed a spatial pre-cueing comparative judgement task that had been frequently used to test the attentional effects on visual perception. The results showed that a smaller stimulus within the focus of exogenous attention was perceived to be equal in size as a larger unattended stimulus, whereas a larger stimulus within the focus of endogenous attention was perceived to be equal in size as a smaller unattended stimulus. In other words, exogenous attention increased the perceived size while endogenous attention decreased the perceived size. The contrasting effects may be attributed to the mechanism that exogenous attention favours parvocellular processing for which more neurons with smaller receptive fields (RFs) are activated for a given size, whereas endogenous attention favours magnocellular processing for which fewer neurons with larger RFs are activated. This finding shows that exogenous and endogenous attention acts differentially on size perception, and provides supportive evidence for the distinct mechanisms underlying the two types of attentional processing.
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Affiliation(s)
- Yifei Han
- Department of Psychology, Sun Yat-Sen University, Guangzhou, China.,State Key Laboratory of Brain and Cognitive Science, Institute of Psychology, Chinese Academy of Sciences, Beijing, China.,Department of Psychology, University of Chinese Academy of Sciences, Beijing, China
| | - Zhihao Tan
- Department of Psychology, Sun Yat-Sen University, Guangzhou, China
| | - Huang Zhuang
- Department of Psychology, Sun Yat-Sen University, Guangzhou, China
| | - Jiehui Qian
- Department of Psychology, Sun Yat-Sen University, Guangzhou, China
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11
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Kirsch W, Kunde W. On the origin of the Ebbinghaus illusion: The role of figural extent and spatial frequency of stimuli. Vision Res 2021; 188:193-201. [PMID: 34364022 DOI: 10.1016/j.visres.2021.07.016] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/21/2021] [Revised: 07/20/2021] [Accepted: 07/27/2021] [Indexed: 11/17/2022]
Abstract
An object is perceived as larger when it is surrounded by smaller context objects than when it is surrounded by larger context objects. The origin of this well-known phenomenon, called as Ebbinghaus or Titchener circles illusion, is still puzzling. Here we introduce a basic explanation of how this illusion could emerge and provide some preliminary empirical support for this idea. In essence, we suggest that changes in the figural extent and in the spatial frequency of the stimulus pattern entail adjustments of the size and resolution of the attentional field, which are accompanied by changes in spatial coding. This approach is consistent with previous observations and can enable a deeper understanding of geometric illusions.
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Affiliation(s)
| | - Wilfried Kunde
- Department of Psychology, University of Würzburg, Germany
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12
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Abstract
The present study explored the origin of perceptual changes repeatedly observed in the context of actions. In Experiment 1, participants tried to hit a circular target with a stylus movement under restricted feedback conditions. We measured the perception of target size during action planning and observed larger estimates for larger movement distances. In Experiment 2, we then tested the hypothesis that this action specific influence on perception is due to changes in the allocation of spatial attention. For this purpose, we replaced the hitting task by conditions of focused and distributed attention and measured the perception of the former target stimulus. The results revealed changes in the perceived stimulus size very similar to those observed in Experiment 1. These results indicate that action’s effects on perception root in changes of spatial attention.
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13
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Abstract
Although spatial attention has been found to alter the subjective appearance of visual stimuli in several perceptual dimensions, no research has explored whether exogenous spatial attention can affect depth perception, which is a fundamental dimension in perception that allows us to effectively interact with the environment. Here, we used an experimental paradigm adapted from Gobell and Carrasco (Psychological Science, 16[8], 644-651, 2005) to investigate this question. A peripheral cue preceding two line stimuli was used to direct exogenous attention to either location of the two lines. The two lines were separated by a certain relative disparity, and participants were asked to judge the perceived depth of two lines while attention was manipulated. We found that a farther stereoscopic depth at the attended location was perceived to be equally distant as a nearer depth at the unattended location. No such effect was found in a control experiment that employed a postcue paradigm, suggesting that our findings could not be attributed to response bias. Therefore, our study shows that exogenous spatial attention shortens perceived depth. The apparent change in stereoscopic depth may be regulated by a mechanism involving direct neural enhancement on those tuned to disparity, or be modulated by an attentional effect on apparent contrast. This finding shows that attention can change not only visual appearance but also the perceived spatial relation between an object and an observer.
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