Pathological left-handedness: is it familial?

Area of Science:

• Neuroscience
• Genetics
• Developmental Psychology

Background:

• Hand preference, particularly left-handedness, has been studied in relation to cognitive and developmental conditions.
• Existing theories propose a distinction between pathological left-handedness in special populations and familial left-handedness in the general population.

Purpose of the Study:

• To compare the incidence of hand preferences and familial sinistrality (left-handedness) between developmentally retarded individuals (including Down syndrome) and non-retarded individuals.
• To investigate whether the observed patterns of left-handedness in special groups align with established theories.

Main Methods:

• Comparative analysis of hand preference data.
• Assessment of familial left-handedness incidence across different developmental groups.

Main Results:

• Developmentally retarded individuals, including those with Down syndrome, exhibited a higher incidence of left-handedness compared to non-retarded individuals.
• The incidence of familial left-handedness was also elevated in the developmentally retarded groups.

Conclusions:

• The study's findings contradict the theoretical separation of pathological and familial left-handedness.
• Left-handedness in individuals with developmental disabilities may share common etiological factors with familial left-handedness.