We wore ankle-length blue coats at my school, in the Tudor-style. When it rained, the wool of the coat gave off a pungent smell, rather like wet dog. Now when I encounter a similar scent, it propels me back in time to my school days. This effect is called the "Proustian phenomenon". The name comes from Proust's description in Remembrance of Things Past of how the smell of a tea-soaked madeleine biscuit transported him back in time to his childhood.

Smells do have this uncanny, evocative power, don't they? It's because of the relative proximity of the olfactory bulb (which processes smells) and the hippocampus and amygdala, which are involved in memory and emotions. Right?

Not so fast. In fact very little research has investigated whether smells really do evoke vivid and emotional memories, more than other sensory cues. What follows is a new, rare attempt.

Marieke Toffolo and her collaborators invited 70 female student participants to watch a disturbing 12-minute film featuring road traffic accidents, surgery and reports on the Rwandan genocide. Whilst the students watched the film, the smell of Cassis, a neutral berry-like odour, was sprayed into the room; coloured lights were projected onto the back wall; and inoffensive background music was played over speakers (no mention was made to the students of these cues; pilot work established that they were equally noticeable, pleasant and arousing). The researchers chose to focus only on female participants to keep things simple, because it's known that there are sex differences in olfactory perception.

A week later the students were called back and asked to write down as many memories about the film as they could. As they did so, either the smell, the lights or the music were presented again. The students also answered questions about the quality of their memories. The main finding is that students exposed again to the smell of Cassis rated their memories of the film as more detailed, unpleasant and arousing (but no more transporting or vivid) than students re-exposed to the music. However, the students re-exposed to the odour rated their memories no differently from students re-exposed to the lights. In other words, smell appeared to be more evocative than music, but no more evocative than lights.

"It could be argued that a necessary implication of the Proust phenomenon is that odours are more effective triggers of emotional memories than other-modality triggers," the researchers said. "Under such strong assumptions the results reported here do not confirm the Proust phenomenon. Nonetheless, our findings do extend previous research by demonstrating that odour is a stronger trigger of detailed and arousing memories than music, which has often been held to provide equally powerful triggers as odours."

Toffolo, M., Smeets, M., and van den Hout, M. (2012). Proust revisited: Odours as triggers of aversive memories. Cognition and Emotion, 26 (1), 83-92 DOI:
 What smells do you remember from your childhood and what memories do they evoke?