The perception of smell consists not only of the sensation of the odours themselves but of the experiences and emotions associated with these sensations. Smells can evoke strong emotional reactions. In surveys on reactions to odours, responses show that many of our olfactory likes and dislikes are based purely on emotional associations.
The association of fragrance and emotion is not an invention of poets or perfume-makers. Our olfactory receptors are directly connected to the limbic system, the most ancient and primitive part of the brain, which is thought to be the seat of emotion. Smell sensations are relayed to the cortex, where ‘cognitive’ recognition occurs, only after the deepest parts of our brains have been stimulated. Thus, by the time we correctly name a particular scent as, for example, ‘vanilla’ , the scent has already activated the limbic system, triggering more deep-seated emotional responses.
Although there is convincing evidence that pleasant fragrances can improve our mood and sense of well-being, some of these findings should be viewed with caution. Recent studies have shown that our expectations about an odour, rather than any direct effects of exposure to it, may sometimes be responsible for the mood and health benefits reported. In one experiment, researchers found that just telling subjects that a pleasant or unpleasant odour was being administered, which they might not be able to smell, altered their self-reports of mood and well-being. The mere mention of a positive odour reduced reports of symptoms related to poor health and increased reports of positive mood!
More reliable results have been obtained, however, from experiments using placebos (odourless sprays). These studies have demonstrated that although subjects do respond to some extent to odourless placebos which they think are fragrances, the effect of the real thing is significantly greater. The thought of pleasant fragrances may be enough to make us a bit more cheerful, but the actual smell can have dramatic effects in improving our mood and sense of well-being.
Although olfactory sensitivity generally declines with age, pleasant fragrances have been found to have positive effects on mood in all age groups.
In experiments involving stimulation of the left and right nostrils with pleasant and unpleasant fragrances, researchers have found differences in olfactory cortical neurone activity in the left and right hemispheres of the brain which correlate with the ‘pleasantness ratings’ of the odorants. These studies are claimed to indicate that positive emotions are predominantly processed by the left hemisphere of the brain, while negative emotions are more often processed by the right hemisphere. (The ‘pleasant’ odorant used in these experiments, as in many others, was vanillin.)
The positive emotional effects of pleasant fragrances also affect our perceptions of other people. In experiments, subjects exposed to pleasant fragrances tend to give higher ‘attractiveness ratings’ to people in photographs, although some recent studies have shown that these effects are only significant where there is some ambiguity in the pictures. If a person is clearly outstandingly beautiful, or extremely ugly, fragrance does not affect our judgement. But if the person is just ‘average’, a pleasant fragrance will tip the balance of our evaluation in his or her favour. So, the beautiful models used to advertise perfume probably have no need of it, but the rest of us ordinary mortals might well benefit from a spray or two of something pleasant. Beauty is in the nose of the beholder.
Unpleasant smells can also affect our perceptions and evaluations. In one study, the presence of an unpleasant odour led subjects not only to give lower ratings to photographed individuals, but also to judge paintings as less professional.
The mood-improving effects of pleasant smells may not always work to our advantage: by enhancing our positive perceptions and emotions, pleasant scents can cloud our judgement. In an experiment in a Las Vegas casino, the amount of money gambled in a slot machine increased by over 45% when the site was odorised with a pleasant aroma!
In another study – a consumer test of shampoos – a shampoo which participants ranked last on general performance in an initial test, was ranked first in a second test after its fragrance had been altered. In the second test, participants said that the shampoo was easier to rinse out, foamed better and left the hair more glossy. Only the fragrance had been changed.
Scent-preferences are often a highly personal matter, to do with specific memories and associations. In one survey, for example, responses to the question ‘What are your favourite smells?’ included many odours generally regarded as unpleasant (such as gasoline and body perspiration), while some scents usually perceived as pleasant (such as flowers) were violently disliked by certain respondents. These preferences were explained by good and bad experiences associated with particular scents. Despite these individual peculiarities, we can make some significant generalisations about smell-preference. For example, experiments have shown that we tend to ‘like what we know’: people give higher pleasantness ratings to smells which they are able to identify correctly. There are also some fragrances which appear to be universally perceived as ‘pleasant’ – such as vanilla, an increasingly popular ingredient in perfumes which has long been a standard ‘pleasant odour’ in psychological experiments (see Vanilla).
A note for perfume-marketers: one of the studies showing our tendency to prefer scents that we can identify correctly also showed that the use of an appropriate colour can help us to make the correct identification, thus increasing our liking for the fragrance. The scent of cherries, for example, was accurately identified more often when presented along with the colour red – and subjects’ ability to identify the scent significantly enhanced their rating of its pleasantness.