Crowding

For the medical sociology concept, see Overcrowding.
A demonstration of the crowding effect. Fixate on the "x" and attempt to identify the central (or single) letter appearing to the right. The presence of flankers should make the task more difficult.

Crowding (or visual crowding) is a perceptual phenomenon where the recognition of objects presented away from the fovea is impaired by the presence of other neighbouring objects (sometimes called "flankers").[1] It has been suggested that crowding occurs due to mandatory integration of the crowded objects by a texture-processing neural mechanism,[2] but there are several competing theories about the underlying mechanisms.[3][4][5][6][7] It is considered a kind of grouping[8] since it is "a form of integration over space as target features are spuriously combined with flanker features."[9]

Crowding has long been thought to be predominantly a characteristic of peripheral vision. Yet, while it is indeed particularly prominent there, it is present in the whole of the visual field, with only its spatial extent varying (governed by Bouma's law; see below).[10] In particular, crowding is of utmost importance in foveal vision,[11] overriding the importance of visual acuity in pattern recognition and reading where crowding represents the bottleneck in processing.[12][4][10]

Crowding is prominently present in amblyopia and has been first mentioned in that context[13][10] and studied quantitatively there.[14] Crowding deficits have further been found in neuropsychiatric disorders such as schizophrenia and autism and may have clinical implications in these disorders.[15] It is also suggested that head injuries can cause a crowding effect.[16] Normally sighted children up to the age of about eight years further have more pronounced crowding than adults,[17] and this may be the reason for larger print in children's books.

  1. ^ Levi D (February 2008). "Crowding - an essential bottleneck for object recognition: a mini-review". Vision Research. 48 (5): 635–654. doi:10.1016/j.visres.2007.12.009. PMC 2268888. PMID 18226828.
  2. ^ Parkes L; Lund J; Angelucci A; Solomon JA; Morgan M (2001). "Compulsory averaging of crowded orientation signals in human vision". Nature Neuroscience. 4 (7): 739–744. doi:10.1038/89532. PMID 11426231. S2CID 10975462.
  3. ^ Tyler, C.W.; Likova, L.T. (2007). "Crowding: A neuroanalytic approach". Journal of Vision. 7 (2:16): 1–9. doi:10.1167/7.2.16. PMID 18217831.
  4. ^ a b Cite error: The named reference Levi_2008 was invoked but never defined (see the help page).
  5. ^ Strasburger, H. (2014). "Dancing letters and ticks that buzz around aimlessly – On the origin of crowding". Perception. 43 (9): 963–976. doi:10.1068/p7726. PMID 25420335. S2CID 26136221.
  6. ^ Rosenholtz, R. (2016). "Capabilities and limitations of peripheral vision". Annual Review of Vision Science. 2: 437–457. doi:10.1146/annurev-vision-082114-035733. PMID 28532349. S2CID 207728323.
  7. ^ Strasburger, H. (2020). "On the cortical mapping function (Preprint)". bioRxiv. doi:10.1101/621458. S2CID 149700090.
  8. ^ Herzog, M. H.; Sayim, B.; Chicherov, V.; Manassi, M. (2015). "Crowding, grouping, and object recognition: A matter of appearance". Journal of Vision. 15 (6:5): 1–18. doi:10.1167/15.6.5. PMC 4429926. PMID 26024452.
  9. ^ Wixted, John (2018). Stevens' Handbook of Experimental Psychology and Cognitive Neuroscience, Sensation, Perception, and Attention, Fourth Edition Volume 2. Hoboken, NJ: John Wiley & Sons. p. 833. ISBN 9781119170044.
  10. ^ a b c Strasburger, Hans (2020). "Seven myths on crowding and peripheral vision". i-Perception. 11 (2): 1–45. doi:10.1177/2041669520913052. PMC 7238452. PMID 32489576.
  11. ^ Foveal vision refers to the situation where the observer fixates a visual object and, depending on the latter, uses anything between the tiny region of highest acuity (in acuity measurements) or the whole of the fovea and more (in reading) for processing the visual input.
  12. ^ Pelli, D.G.; Tillman, K.A.; Freeman, J.; Su, M.; Berger, T.D.; Majaj, N.J. (2007). "Crowding and eccentricity determine reading rate". Journal of Vision. 7 (2:20): 1–36. doi:10.1167/7.2.20. PMID 18217835.
  13. ^ Ehlers, Holger (1936). "The movements of the eyes during reading". Acta Ophthalmologica. 14: 56–63. doi:10.1111/j.1755-3768.1936.tb07306.x. S2CID 73409510.
  14. ^ Stuart, J.A.; Burian, H.M. (1962). "A study of separation difficulty: its relationship to visual acuity in normal and amblyopic eyes". American Journal of Ophthalmology. 53: 471–477. doi:10.1016/0002-9394(62)94878-X. PMID 13917936.
  15. ^ Kraehenmann, Rainer; Vollenweider FX; Seifritz E; Kometer M (2012). "Crowding deficits in the visual periphery of schizophrenia patients". PLOS ONE. 7 (9): e45884. Bibcode:2012PLoSO...745884K. doi:10.1371/journal.pone.0045884. PMC 3458825. PMID 23049884.
  16. ^ Millichap, Gordon (2009). Attention Deficit Hyperactivity Disorder Handbook: A Physician's Guide to ADHD, Second Edition. New York: Springer Science+Business Media. p. 17. ISBN 9781441913968.
  17. ^ Atkinson, J.; Pimm-Smith, E.; Evans, C.; Harding, G.; Braddick, O. (1986). "Visual Crowding in Young Children". Detection and Measurement of Visual Impairment in Pre-Verbal Children. Documenta Ophthalmologica Proceedings Series. Vol. 45. pp. 201–213. doi:10.1007/978-94-009-4263-9_27. ISBN 978-94-010-8393-5.