Long-term studies of twins and adopted children suggest that "genetic factors" may predispose individuals to chronic criminal behavior, a California researcher said yesterday.
Dr. Sarnoff Mednick, a University of Southern California psychologist, stressed, however, that inheritance in no ways condemns a person to become a lifelong criminal.
"Child rearing and social factors are critical in helping determine whether this biological predisposition will be realized," he told the American Association for the Advancement of Science, adding that the "expression of genetic factors" was likely to be "less in the lower classes" because there is more exposure to adverse environmental factors.
He said that he and others have already identified certain physical characteristics, reflective of nervous system differences, which could help predict whether children are at increased risk of later becoming habitual criminals.
Mednick, who also directs the Psychological Institute in Copenhagen, urged that additional research be conducted so that this group could be identified "quite early in their careers" and offered "preventive intervention programs" that he contended could "have a marked effect on overall crime rates."
The sensitive implications of the federally funded research are likely to come under fire because of longstanding concerns about the dangers of labeling individuals as criminals or interfering with their civil rights.
Carnegie-Mellon crime expert Alfred Blumstein, a member of the AAAS panel, expressed concern about the "legitimacy and effectiveness of intervention." Dr. Edith Flynn, who moderated the AAAS panel, called his findings "controversial," but added that the research should not be "suppressed" because it is "potentially offensive."
Mednick's reputation was praised by Flynn and other scientists, including Dr. Melvin Sabshin, medical director of the American Psychological Association, and Dr. Saleem Shah, director of the Center for Studies of Crime and Delinquency at the National Institute of Mental Health.
Although he has not yet received a final report, Shah noted that "not only on the basis of Mednick's study but other studies, there does appear to be a genetic component influencing problem behavior." Shah added that intervention is a "separate issue," which could be subject to potential "abuse."
Mednick also emphasized that any future attempt at "early detection" of chronic criminals should be "voluntary." He said that the "overriding consideration is not to erode our civil rights."
His conclusion that there is a strong genetic component to repeat criminal behavior is based upon numerous studies with twins, including one in which identical pairs were shown to be about three times as likely to share criminal behavior as are fraternal twins.
Even "more convincing," he contended, is an extensive study he has conducted of over 14,000 children adopted in Denmark between 1924 and 1947 and their later criminal records. He found that the repeat criminal behavior "agrees more with that of the biological parents than that of adoptive parents" and that a biological parent who is a repeat criminal "greatly increases" the chance the child will be also. The link is apparently stronger for crimes of property, such as theft and burglary.
He found that environmental influences appeared to be stronger than genetics for boys with the opposite true for girls.