Effects of handedness and script types on visual-field differences in the mental addition task

Area of Science:

• Cognitive Psychology
• Neuroscience
• Linguistics

Background:

• Cerebral lateralization, the dominance of one brain hemisphere for certain functions, varies between individuals.
• Handedness is often used as an indicator of brain lateralization, but its relationship with cognitive tasks, especially across different writing systems, is complex.

Purpose of the Study:

• To investigate the influence of handedness and numeral script types (Arabic, Kanji, Mixed) on visual field performance in a mental addition task.
• To explore differences in cerebral lateralization patterns between right-handers and left-handers (familial and nonfamilial) using a Japanese language context.

Main Methods:

• Participants (right-handers, familial left-handers, nonfamilial left-handers, native Japanese speakers) performed mental addition of two numbers presented tachistoscopically in either the left or right visual field, or center.
• Number stimuli were presented in Arabic numerals, Kanji numerals, or a mix of both (Mixed stimuli).

Main Results:

• Right-handers exhibited a right visual-field advantage specifically for Arabic numeral conditions.
• No significant visual-field differences were observed for right-handers with Kanji or Mixed stimuli.
• Left-handers (both familial and nonfamilial) showed no visual-field differences across all numeral conditions.

Conclusions:

• The findings indicate distinct patterns of cerebral lateralization for number processing between right-handers and left-handers.
• Cerebral lateralization for left-handers appears consistent, regardless of familial history, and differs from that of right-handers, particularly when processing Arabic numerals.