the time the response to alcohol was measured (Schuckit, 2009; Schuckit et al., 2008a; 2008b; Schuckit et al., in press; Volavka et al., 1996). The ability to control for baseline quantity is an important step to minimize the possibility that a low LR reflects tolerance acquired through a prior pattern of heavier drinking. The heritability of LR as established through family or twin studies is between 40% and 60% (Schuckit et al., 2001; Schuckit et al., 2005; Schuckit et al., 2006).
