Letter identification declines with increasing retinal eccentricity at the same rate for normal and dyslexic readers

Area of Science:

• Cognitive Psychology
• Neuroscience
• Developmental Psychology

Background:

• Previous research suggested dyslexics have a flatter acuity/eccentricity function, performing better in peripheral vision.
• This hypothesis was based on studies with a procedural flaw, presenting targets only to the right of fixation.

Purpose of the Study:

• To investigate if visual acuity differences at varying visual field eccentricities contribute to reading impairments in dyslexia.
• To re-evaluate the acuity/eccentricity function in dyslexic individuals using a methodologically sound approach.

Main Methods:

• Target letters were presented at 16 randomized locations (four eccentricities, four directions: up, down, left, right).
• Participants included dyslexic teenagers and good/poor adult readers.
• Letter identification accuracy was measured at each location.

Main Results:

• Letter identification accuracy decreased with increasing visual eccentricity at a similar rate for all participant groups.
• No significant difference was found in the acuity/eccentricity function between dyslexic and normal readers.

Conclusions:

• The findings do not support the theory that variations in the acuity/eccentricity function are a cause of reading differences.
• This study suggests that visual processing differences in the peripheral visual field are unlikely to explain reading difficulties in dyslexia.