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January 1984

Handedness in Determination of Twin Types-Reply.

Author Affiliations

Psychiatric Hospital University of Iowa Hospitals and Clinics Iowa City, IA 52242

Arch Neurol. 1984;41(1):14. doi:10.1001/archneur.1984.04050130016005

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—I believe that Dr Segal is right. I recall a conversation about 50 years ago with Professor Horatio Hackett Newman of the University of Chicago. Dr Newman, who has published extensively on the subject of twins, advised me that mirror imaging is more frequent in monozygotic than in dizygotic twins, not only in handedness but also in clockwise v counterclockwise hair whorl and in palm prints, some of which are more characteristic of the right hand than of the left. My coauthor and I slipped into the error of grouping handedness resemblance with the other similarities as evidence of monozygosity. I stand corrected and thank Dr Segal for this correction.

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