Shortly before the 1981 questionnaire survey of the Australian twin panel, researchers initiated an alcohol challenge study in which 206 young adult male and female twin pairs were tested with a challenge dose of alcohol (Martin et al. 1985). Schuckit hypothesized that the alcohol reactivity measures that he was using were, at least in part, genetically determined. The Australian Alcohol Challenge Twin Study (AACTS) confirmed significant evidence for genetic effects on body-sway increase and subjective intoxication rating after drinking alcohol, with a combined measure of alcohol reactivity (based on both body-sway and intoxication) showing 60 percent heritability (Heath et al. 1999).
