Do conditioned taste aversions result from activation of emetic mechanisms?

The conditioned taste aversion (CTA) literature is extensive, yet little is known about the mechanisms by which treatments induce CTA. This paper describes and evaluates Garcia's hypothesis (e.g., Garcia et al. 1985) that treatments produce taste aversions by activating the receptors and neural pathways proposed by Borison and Wang (1953) to underlie emesis. Research on the mechanisms by which various treatments induce emesis is reviewed and compared with similar research on CTA. Emetic mechanisms appear to be involved appear to be involved in the formation of CTAs produced by some treatments, but there is contrary evidence for other treatments. This suggests that some CTAs are mediated by emetic mechanisms and others are not, so that Garcia's hypothesis is not generally correct. However, methodological and theoretical ambiguities make it premature to draw this conclusion.