We are pleased that our report has stimulated interest in the risk factors of left-handedness. The study by Professor Hicks and his colleagues should not be viewed as a replication of our study. Two major differences between our studies need to be emphasized. First, although parity and age correlate, they are not equivalent. Hicks et al evaluated maternal age as a risk factor of left-handedness, whereas we evaluated parity (birth order). Thus, in this regard our studies are only tenuously comparable. Bakan1,2 accepts the continuum of casualty hypothesis that risk factors of mortality are, when less intense or frequent, risk factors of more subtle damage to the newborn.3 Although the San Jose group does not accept the continuum of casualty hypothesis, they do use Bakan's terminology of "birth-risk." We have avoided the use of such terms, and suggest that such terms as "high risk pregnancy" do not appear
Leviton A, Kilty T. Birth Risk and Left-Handedness Reconsidered-Reply. Arch Neurol. 1979;36(2):120. doi:10.1001/archneur.1979.00500380090022
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