Handedness and dyslexia: a meta-analysis

Area of Science:

• Neuroscience
• Developmental Psychology
• Genetics

Background:

• The association between handedness and dyslexia has been studied for over 50 years.
• Previous reviews, like Bishop's in 1990, found limited evidence for a link.
• The right-shift theory proposes a biological basis for variations in handedness.

Purpose of the Study:

• To re-evaluate the association between non-right-handedness and dyslexia.
• To determine if newer meta-analysis techniques reveal a reliable link.
• To assess findings in light of the right-shift theory of handedness.

Main Methods:

• Reanalysis of existing studies that met stringent methodological criteria.
• Application of modern meta-analysis procedures.
• Comparison of dyslexic and non-dyslexic populations regarding handedness distribution.

Main Results:

• A small but statistically reliable increase in the proportion of non-right-handers among individuals with dyslexia was found.
• The results support the predictions of Annett's right-shift theory.
• The reanalysis contradicts earlier conclusions of no significant association.

Conclusions:

• There is a reliable association between dyslexia and non-right-handedness.
• The findings support the right-shift theory, suggesting a shared underlying biological mechanism.
• Further research into the neurodevelopmental aspects of handedness and reading disorders is warranted.