The case for the visual span as a sensory bottleneck in reading

Area of Science:

• Cognitive psychology
• Visual perception
• Reading science

Background:

• The visual span is the number of letters readable without eye movements.
• The visual-span hypothesis posits that visual span size limits reading speed.
• Stimulus attributes like character size and contrast may influence reading speed by altering visual span size.

Purpose of the Study:

• To test the prediction that reading speed changes with character size or contrast are mediated by changes in visual span size.
• To investigate the relationship between visual span size and reading speed under varying stimulus conditions.

Main Methods:

• Two experiments measured visual span size and reading speed in five subjects each.
• The trigram method characterized visual span size.
• Rapid Serial Visual Presentation (RSVP) measured reading speed.

Main Results:

• Visual span size and reading speed exhibited similar dependencies on character size and contrast.
• Both measures peaked at the same critical points and showed high inter-subject correlations.
• An increase of one letter in visual span size was associated with a 39% increase in RSVP reading speed.

Conclusions:

• The findings confirm the visual-span hypothesis.
• A theoretical framework is provided for understanding how stimulus attributes affect reading speed.
• Reading speed is influenced by bottom-up sensory limitations, independent of attentional or linguistic factors.