Most of the literature on GXE for behavioral phenotypes in animal models focuses on the role of early experiences or later severe stressors inducing some relatively durable change in the organism. Commonly studied environments in other species include maternal behavior, how enriched or impoverished an environment is, various kinds of physical and social stressors, or early drug exposures (e.g., Barr et al., 2004; Cryan & Slattery, 2007; Holmes et al., 2005; Stevens et al., 2009). While these types of experiences appear relevant to drinking in some animal models (esp. the effect of peer-rearing and early exposure to ethanol in primates; Barr et al., 2004), implicit in all of these types of studies is that environmental exposures are creating some functional (and perhaps even structural) change in the organism that persists for some duration of time and is motivationally relevant to general approach or restraint tendencies. Most GXE interactions are studied within this framework.
