Size Constancy Mechanisms: Empirical Evidence from Touch
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 (alon...
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| Format: | Article |
| Language: | English |
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MDPI AG
2022-07-01
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| Series: | Vision |
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| Online Access: | https://www.mdpi.com/2411-5150/6/3/40 |
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| author | Luigi Tamè Suzuki Limbu Rebecca Harlow Mita Parikh Matthew R. Longo |
| author_facet | Luigi Tamè Suzuki Limbu Rebecca Harlow Mita Parikh Matthew R. Longo |
| author_sort | Luigi Tamè |
| collection | DOAJ |
| description | 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. |
| first_indexed | 2024-03-09T22:12:23Z |
| format | Article |
| id | doaj.art-7a49bb9d62974954b4ea36d4ceedda46 |
| institution | Directory Open Access Journal |
| issn | 2411-5150 |
| language | English |
| last_indexed | 2024-03-09T22:12:23Z |
| publishDate | 2022-07-01 |
| publisher | MDPI AG |
| record_format | Article |
| series | Vision |
| spelling | doaj.art-7a49bb9d62974954b4ea36d4ceedda462023-11-23T19:29:22ZengMDPI AGVision2411-51502022-07-01634010.3390/vision6030040Size Constancy Mechanisms: Empirical Evidence from TouchLuigi Tamè0Suzuki Limbu1Rebecca Harlow2Mita Parikh3Matthew R. Longo4School of Psychology, University of Kent, Canterbury CT2 7NP, UKDepartment of Psychological Sciences, Birkbeck, University of London, London WC1E 7HX, UKDepartment of Psychological Sciences, Birkbeck, University of London, London WC1E 7HX, UKDepartment of Psychological Sciences, Birkbeck, University of London, London WC1E 7HX, UKDepartment of Psychological Sciences, Birkbeck, University of London, London WC1E 7HX, UKSeveral 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.https://www.mdpi.com/2411-5150/6/3/40touchanisotropybody representationssizedistanceconstancy |
| spellingShingle | Luigi Tamè Suzuki Limbu Rebecca Harlow Mita Parikh Matthew R. Longo Size Constancy Mechanisms: Empirical Evidence from Touch Vision touch anisotropy body representations size distance constancy |
| title | Size Constancy Mechanisms: Empirical Evidence from Touch |
| title_full | Size Constancy Mechanisms: Empirical Evidence from Touch |
| title_fullStr | Size Constancy Mechanisms: Empirical Evidence from Touch |
| title_full_unstemmed | Size Constancy Mechanisms: Empirical Evidence from Touch |
| title_short | Size Constancy Mechanisms: Empirical Evidence from Touch |
| title_sort | size constancy mechanisms empirical evidence from touch |
| topic | touch anisotropy body representations size distance constancy |
| url | https://www.mdpi.com/2411-5150/6/3/40 |
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