The smell of fear more powerful than previously realised

The novelists had it right – fear really can fill the air. Research shows smelling the odour of a scared person triggers activity in a swathe of emotion-related regions in the brain of the sniffer, and leads them to sniff harder and express a fearful facial expression. Still you have to wonder about the real-life impact of this effect. Fear is usually accompanied by the sight and sound of anxiety and we tend to think of these signals as dominant. Would the smell of fear really make much of an impact if it was experienced in the context of sights and sounds signalling no threat? No-one has looked into this before.

Jasper de Groot presented 30 right-handed women with neutral or scary clips of a woman – i.e. either chatting to a man or being assaulted by a man. At the same time, the participants were exposed either to a neutral odour or to the smell of fear. The odours were collected earlier from men's armpits as they watched scary film clips or a BBC nature documentary. The researchers chose female participants for the observation part of this study because they're known to have a superior sense of smell than men. Also, a female researcher dealt with the participants "as the presence of a male experimenter could increase female participants' mood." In science you can never be too careful.

Consistent with past research, the women couldn't tell the difference at a conscious level between the neutral and scary odours. But the take-home result is that the smell of fear led them to pull fearful facial expressions of their own (as recorded by electrodes on their face), and this was the case even when they were watching a neutral video clip. Watching a scary clip with a neutral smell provoked the same intensity of fearful expressions. Finally, a scary clip plus the smell of fear was additive leading to fearful expressions that were even more intense. This facial reaction in the women makes sense from a survival perspective, the researchers said – "raising the eyebrows and upper eye-lids increases a person's visual field size and instigates sensory vigilance processes."

de Groot's team said their results "argue against the commonly accepted view that human communication of emotions runs exclusively via linguistic or visual channels." Lots of questions remain for future research – for instance, would the same results apply for men exposed to fear odours collected from women?

Further reading

de Groot JH, Semin GR, and Smeets MA (2013). I Can See, Hear, and Smell Your Fear: Comparing Olfactory and Audiovisual Media in Fear Communication. Journal of experimental psychology. General PMID: 23855495