title: The effect of aging on crowded letter recognition in the peripheral visual field.
abstract: OBJECTIVE
  Crowding describes the increased difficulty in identifying a target object when it is surrounded by nearby objects (flankers). A recent study investigated the effect of age on visual crowding and found equivocal results: Although crowded visual acuity was worse in older participants, crowding expressed as a ratio did not change with age. However, the spatial extent of crowding is a better index of crowding effects and remains unknown. In the present study, we used established psychophysical methods to characterize the effect of age on visual crowding (magnitude and extent) in a letter recognition task.
  
  
  METHODS
  Letter recognition thresholds were determined for three different flanker separations in 54 adults (aged 18-76 years) with normal vision. Additionally, the spatial extent of crowding was established by measuring spacing thresholds: the flanker-to-target separation required to produce a given reduction in performance. Uncrowded visual acuity, crowded visual acuity, and spacing thresholds were expressed as a function of age, avoiding arbitrary categorization of young and old participants.
  
  
  RESULTS
  Our results showed that uncrowded and crowded visual acuities do not change significantly as a function of age. Furthermore, spacing thresholds did not change with age and approximated Bouma's law (half eccentricity).
  
  
  CONCLUSIONS
  These data show that crowding in adults is unaffected by senescence and provide additional evidence for distinct neural mechanisms mediating surround suppression and visual crowding, since the former shows a significant age effect. Finally, our data suggest that the well-documented age-related decline in peripheral reading ability is not due to age-related changes in visual crowding.
authors.affiliation: Visual Neuroscience Group, School of Psychology, University of Nottingham, Nottingham, United Kingdom.
authors.forename: Andrew T
authors.initials: AT
authors.lastname: Astle
authors.affiliation: Visual Neuroscience Group, School of Psychology, University of Nottingham, Nottingham, United Kingdom.
authors.forename: Alan J
authors.initials: AJ
authors.lastname: Blighe
authors.affiliation: Visual Neuroscience Group, School of Psychology, University of Nottingham, Nottingham, United Kingdom.
authors.forename: Ben S
authors.initials: BS
authors.lastname: Webb
authors.affiliation: Visual Neuroscience Group, School of Psychology, University of Nottingham, Nottingham, United Kingdom.
authors.forename: Paul V
authors.initials: PV
authors.lastname: McGraw
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D000375:Aging / Q000502:physiology*; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D010364:Pattern Recognition, Visual / Q000502:physiology*; D010470:Perceptual Masking / Q000502:physiology*; D011601:Psychophysics / Q000379:methods; D011932:Reading; D012016:Reference Values; D013028:Space Perception; D014792:Visual Acuity; D014794:Visual Fields; D055815:Young Adult
keywords: aging; critical spacing; crowding; reading; visual acuity