Mean mortality among Brazilian left- and right-handers: Modification or selective elimination?

Abstract

Many surveys report a higher incidence of left-handedness in younger than in older cohorts, and explanations for this phenomenon have centred around two rival hypotheses. The modification hypothesis attributes this trend to secular differences in the social tolerance of left-handed preferences, whereas the elimination hypothesis contends that left-handers have a shorter life-span than right-handers do, and hence are infrequent in the population above age 70. In order to evaluate these two hypotheses, data were collected on 513 decedents from kin informants. There were 465 right- and 48 left-handed decedents, including 18 switched sinistrals. Females lived significantly longer than males, and there was a nonsignficant survival advantage for left-handers. Switched left-handers were disproportionately represented among older compared to younger decedents, indicating an historical reduction of sanctions against left-handed writing. These results contradict the survival advantage for right-handers reported by Coren and Halpern (1991), providing evidence more favourable to a cultural conditioning explanation, rather than one emphasising selective mortality.