Does olfactory memory depend on remembering odors?

The question mark in the title indicates that what follows is not a theory explaining odor memory, but a series of findings that question the traditional view of memory, in which acquisition and retrieval of ‘memory items’ dominate all questions asked. That such questions arise in an area that deals with odors is not surprising. Odors are the least palpable and most evanescent of stimuli. Odors are not ‘things’, unlike visual, auditory and tactile stimuli they do not have structured properties in space and/or time. Odors are notoriously hard to describe, classify and identify. We are surrounded by an almost infinite number of odors, although we usually do not pay attention to them. Our houses, our cities and we ourselves all smell different. We live amidst smells without noticing unless something happens that changes them. Lending your house or car to friends, a slight change in the flavor of your favorite marmalade are reminders that you have a good memory for odors that you could nevertheless not describe in any detail. Strangely enough, incidentally learned implicit odor memory has hardly been investigated. Most studies (see Herz and Engen, 1996; White, 1998) deal with remembering well-known odors presented under controlled laboratory conditions. Often subjects were instructed to inspect the odors attentively, to identify or to memorize them for later memory tests. Other studies explicitly associated odors with pictures or words to test the influence of smelling these odors on memory for the other stimuli or investigated the role of odors in evoking autobiographical memories. The few studies on spontaneous odor or flavor memory in everyday situations (Baeyens et al., 1996; Aggleton and Waskett, 1999; Haller et al., 1999; Garcia et al., 2001) showed that memory may have widespread and long-lasting effects, even if during learning no conscious effort at feature analysis or memorizing is made.