Unconscious Smells Tell You if You Like Somebody or Not

Just by a sniff, a dog can tell if you're a chicken or a trusty person, if it's better to avoid you or to beg for food and affection. But, a new research, made at the Northwestern University and published in the "Psychological Science" journal, showed that humans used infinitesimal scents, too, for assessing if they liked somebody or not.

"We evaluate people every day and make judgements about who we like or don�t like. We may think our judgements are based only on various conscious bits of information, but our senses also may provide subliminal perceptual information that affects our behavior." said lead author Wen Li, a post-doctoral fellow in the Cognitive Neurology and Alzheimer's Disease Centre, at Northwestern Feinberg School of Medicine.

In order to verify this, researchers put subjects to sniff bottles with 3 different scents: lemon (good), sweat (bad) and ethereal (neutral). The concentrations of the chemicals varied from doses that could be consciously perceived to those barely smelled. Most subjects were not aware of the smell in the case of the lowest concentrations.

After sniffing from each of the bottles, the subjects were presented a neutral expression face and had to score its likability in a scale of one to six, from extremely likable to extremely unlikeable. People that were slightly better than the average at perceiving the minimal smell were not influenced by the subliminal scents.

"The study suggests that people conscious of the barely noticeable scents were able to discount that sensory information and just evaluate the faces. It only was when smell sneaked in without being noticed that judgements about likability were biased." said Li.

This matches the results of recent researches showing that in the case of visual stimuli brain's top-down control mechanisms work in an unconscious level, individuals being not aware of this control. And this seems to be valid to hearing, as well.

"When sensory input is insufficient to provoke a conscious olfactory experience, subliminal processing prevails and biases perception. But as the awareness of a scent increases, greater executive control in the brain is engaged to counteract unconscious olfaction." said co-author Ken Paller, professor of psychology in the Weinberg College of Arts and Sciences at Northwestern.

"In general, people tend to be dismissive of human olfaction and discount the role that smell plays in our everyday life. Our study offers direct evidence that human social behavior is under the influence of minuscule amounts of odor, at concentrations too low to be consciously perceived, indicating that the human sense of smell is much keener than commonly thought." said senior author Jay Gottfried, assistant professor of neurology at Feinberg.