Australasian Science: Australia's authority on science since 1938

Scent of a Woman

By Tim Hannan

Does the lack of a sense of smell affect personal and sexual relationships?

The olfactory sense serves various functions. It influences food choice and appreciation, and assists in the detection of environmental dangers.

Its role in social behaviour is not understood well, but a study recently published in the journal Biological Psychology has suggested that those with a congenital disability in smell are affected in their social and sexual relationships. A team of German researchers led by Ilona Croy reported that those with reduced or absent sense of smell demonstrated a lower sense of security in social and intimate relationships, with affected men reporting markedly fewer sexual partners than healthy participants.

Although it is the least acute of the human senses, olfaction is known to provide the ability to detect as many as 10,000 different odours, even at low concentrations. Gastronomes may demonstrate even greater abilities in odour detection and discrimination.

Of course, the olfactory system of many animals is superior to humans due to a larger number of receptors in the olfactory epithelium. The average cat has about eight to ten times as many receptors as a human – as well as a larger number of neurons devoted to olfactory processing.

It has long been known that olfaction affects various neuropsychological systems, as well as involuntary visceral and homeostatic behaviours. Receptor neurons in the nasal cavity’s epithelium connect directly to both cortical and subcortical areas, enabling the detection of odours to influence learning, memory and emotion.

The association between smells, memories and feelings is well established. Most people have the experience of old memories triggered by specific aromas, even if few are driven by the Proustian impulse to compose seven volumes of reminiscences after dipping a madeleine cake in tea.

Research on individual differences in olfaction has found that women detect odours at lower concentrations and perform better at odour identification than men, though generally the reported sex differences are not large. With regard to social relationships, women state that a potential partner’s smell is more important than appearance in choosing a mate; men report the opposite view.

Given these important functions of the olfactory sense, how do people with an impaired sense of smell fare in social relationships? The study by Croy and colleagues compared 32 individuals with impaired olfaction – termed isolated congenital anosmia (ICA) – to matched controls. While no difference was found in the participants’ reports of eating behaviour or environmental hazards, the ICA group reported a greater insecurity about social relationships. The magnitude of this effect was largest in women, who reported greater insecurity regarding all social relationships, and in particular felt less secure about their partners.

The researchers proposed that those with a reduced sense of smell may be less skilled at reading social cues from others’ behaviour. Other studies have suggested that people are sensitive to chemosensory emotional signals, and that this ability to “smell fear” has a significant impact on social interaction. Another possibility is that those with an impaired sense of smell are socially insecure as a result of uncertainty over how they smell to others.

For men, the ICA and healthy groups differed markedly in their reported number of sexual relationships. Healthy men reported an average of five times the number of lifetime sexual relationships than men with ICA. The authors speculated that greater social insecurity may influence men’s explorative sexual behaviour, or that impaired olfaction may directly affect the selection and success of men’s mating strategies. Another study has linked impaired olfaction in men to reduced sexual desire, though not to sexual satisfaction.

It has also been shown that many people enjoy smelling the clothes of loved ones, particularly in their absence. In one survey of young adults, 52% of women and 13% of men reported sleeping dressed in another’s clothing because of the smell; usually the clothing’s owner was a romantic partner.

Together with the Croy study, these investigations add weight to the claim that olfactory information plays a major role in social relationships. For women, smelling their partner seems to be particularly important to the security of their relationship. For men it may affect the chances of obtaining a partner.

Tim Hannan is an Associate Professor of Clinical Psychology at Charles Sturt University, and the President of the Australian Psychological Society.