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

• Published in: Journal of experimental child psychology 2010-12, Vol.107 (4), p.423-437
• Main Authors: Jeon, Seong Taek, Hamid, Joshua, Maurer, Daphne, Lewis, Terri L.
• Format: Article
• Language: English
• Subjects: Adolescent; Adult; Adults; Age Differences; Age Factors; Biological and medical sciences; Brain; Change; Child; Child Development; Child Development - physiology; Child, Preschool; Children; Comparative Analysis; Crowding; Development; Developmental psychology; Female; Fundamental and applied biological sciences. Psychology; Humans; Male; Pattern Recognition, Visual - physiology; Preadolescents; Psychology. Psychoanalysis. Psychiatry; Psychology. Psychophysiology; Psychophysics; Reading Rate; Recognition (Psychology); Recognition (Psychology) - physiology; Sensory perception; Single-letter acuity; Task Performance and Analysis; Visual Acuity; Visual Acuity - physiology; Visual perception; Visualization; Young Adult; Young Children
• ISSN: 0022-0965; 1096-0457
• DOI: 10.1016/j.jecp.2010.05.009

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 5years 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.