Dissociating spatial and letter-based word length effects observed in readers' eye movement patterns

Area of Science:

• Cognitive Psychology
• Psycholinguistics
• Human-Computer Interaction

Background:

• Previous eye movement research on word length effects has confounded spatial width with the number of letters.
• McDonald (2006) attempted to unconfound these factors by using constant spatial width for all words.

Purpose of the Study:

• To investigate the distinct contributions of the number of letters and spatial width to word length effects in reading.
• To determine how these factors influence fixation duration, location, and word skipping.

Main Methods:

• Utilized Arial font (proportional spacing) to vary letter count while maintaining constant spatial width.
• Employed Courier font (monospaced spacing) to assess the impact of spatial width on reading behavior.
• Measured single fixation duration, fixation locations, and word skipping probability.

Main Results:

• The number of letters in a word significantly affected single fixation duration.
• The spatial width of a word determined fixation locations within the word.
• Spatial width also influenced the probability of skipping a word.

Conclusions:

• The findings support the existence of distinct subsystems for visual attention control during reading (where and when to move eyes).
• The number-of-letters effect on fixation duration may be attributed to visual acuity, crowding, or serial letter processing.