On the scent
New Scientist, 08 January 2000
PEOPLE feel differently about a smell depending on which nostril they sniff it through, say scientists in the US.
Cahill of the University of California at Irvine and his colleagues
asked 32 volunteers to sniff eight common odours, including lemon and
peppermint. The volunteers had to smell the odours through one nostril
and rate them for pleasantness on a scale of -5 to +5, and also try to
identify them. They came back later to repeat the test with the other
When a smell was inhaled through the right nostril, it
was rated on average as more pleasant than when sniffed through the
left. But the left nostril was more accurate when the volunteers were
trying to identify what they were breathing in.
Cahill says the
findings fit with ideas about how the brain processes smells. Earlier
research suggested that each nostril sends almost all its sensory
information to its own side of the brain. Because the right hemisphere
of the brain controls emotional processing, this could explain why
smells might be perceived to have a different degree of pleasantness
when sniffed through the right nostril.
"Your emotional reaction
to an odour actually depends on which hemisphere does the processing,"
Cahill concludes. He hopes to use brain imaging to watch how the two
hemispheres respond to the same odour.