Handedness and lexical skills in undergraduates

Area of Science:

• Neuroscience
• Cognitive Psychology
• Genetics

Background:

• The right shift (RS) theory proposes that genetic factors influence handedness and cerebral dominance, impacting cognitive functions.
• Human dextrality (right-handedness) prevalence is linked to a gene (RS+) facilitating left-hemisphere speech specialization at a potential cost to right-hemisphere function.
• Genotypes RS-- show random brain/hand asymmetries, while RS++ exhibit strong right shift.

Purpose of the Study:

• To investigate the association between patterns of cerebral dominance, as predicted by the RS theory, and specific cognitive function risks.
• To examine the relationship between handedness, phonological processing, and real word homophone discrimination.
• To explore the genetic influence on handedness using sibling comparisons.

Main Methods:

• Three undergraduate samples were assessed using tests for phonological processing and real word homophone discrimination.
• Participants' hand preference was recorded to establish laterality.
• Sibling handedness was analyzed to support the genetic influence hypothesis.

Main Results:

• Phonological processing was weaker on the left of the laterality continuum, while homophone discrimination was weaker on the right.
• Individuals with poor phonology showed less dextral hand preference; those with poor homophone discrimination were more dextral.
• Sibling handedness variations supported a genetic basis for handedness.

Conclusions:

• Cerebral dominance patterns, influenced by the right shift (RS) theory, are associated with differential risks in cognitive functions like phonology and homophone discrimination.
• Handedness, influenced by genetic factors, correlates with specific cognitive strengths and weaknesses.
• The findings support the RS theory's explanation for handedness and its implications for cognitive specialization.