Developmental changes during childhood in single letter-acuity and its crowding by surrounding contours

Seon Taek Jeon, Joshua Hamid, Daphne Maurer, Terri L. Lewis

Research output: Contribution to journalArticlepeer-review

57 Citations (Scopus)


Crowding refers to impaired target recognition caused by surrounding contours. We investigated the development of crowding in central vision by comparing single-letter and crowding thresholds in groups of 5-year-olds, 8-year-olds, 11-year-olds, and adults. The task was to discriminate the orientation of a Sloan letter E. Single-letter thresholds, defined as the stroke width forming the smallest discriminable E, were worse than those of adults (0.83 arcmin) at 5 years of age (1.05 arcmin) but not at older ages (8-year-olds: 0.81 arcmin; 11-year-olds: 0.78 arcmin). The maximum distances over which crowding occurred, as measured in multiples of threshold stroke width, were smaller in adults (2.83) than in the three groups of children, who did not differ from each other (5-year-olds: 7.03; 8-year-olds: 7.84; 11-year-olds: 7.13). Thus, even 11-year-olds are more affected than adults by surrounding contours despite having single-letter acuity that has been mature for several years. The stronger influence of crowding in children may be caused by immaturities in the brain areas beyond the primary visual cortex (V1) where early visual inputs are combined and may contribute to their slower reading speed.
Original languageEnglish
Pages (from-to)423-437
Number of pages15
JournalJournal of Experimental Child Psychology
Early online date14 Jul 2010
Publication statusPublished - Dec 2010


  • visual perception
  • single letter acuity
  • crowding


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