The acquisition of odour preferences via evaluative olfactory conditioning: Historical background and state of the art.

Odours are powerful in bringing back distant memories linked to emotional content. This inherent hedonic property of olfactory stimuli, together with poor accessibility to semantic processing and language, makes odour particularly suitable for studies on evaluative conditioning, a variant of Pavlovian classical conditioning, through which a neutral stimulus acquires the affective valence of another stimulus with which it is paired (Hermans & Baeyens, 2002; Levey & Martin, 1975, 1987). Investigations on olfactory evaluative learning have undergone a surge in recent decades, ranging from literature on taste aversions, emergence of phobias, unconscious and subliminal conditioning, and cross-modal conditioning (De Howver et al., 2001; Li et al., 2007; Rozin et al., 1998; Zucco et al., 2009), to the effect of odour conditioning on consuming attitude, cognitive performance, and somatic syndromes in humans (Schneider et al., 1999; Van den Bergh et al., 1999; Vermetten & Bremner, 2003; Zucco, Militello, & Doty, 2008). The aim of this chapter is, therefore, to examine the most relevant literature on preference acquisition via evaluative olfactory conditioning, from the earliest demonstrations to the most recent investigations.