Odor perception and odor awareness in congenital blindness

It is generally acknowledged that people blind from birth develop supra-normal sensory abilities in order to compensate for their visual deficit. While extensive research has been done on the somatosensory and auditory modalities of the blind, information about their sense of smell remains scant. The goal of this study was therefore to compare odor perception and odor awareness in a group of 11 congenitally blind and 14 sighted control subjects. We measured odor detection threshold, odor discrimination and odor identification using the Sniffin'Sticks test. Participants also filled in the Odor Awareness Scale (OAS) to assess consciousness of olfactory sensations. Our data showed that blind subjects had a lower odor detection threshold compared to the sighted. However, no group differences were found for odor discrimination and odor identification. Interestingly, the OAS revealed that blind participants scored higher for odor awareness. The largest group differences were found for items of the OAS that measure responses to body odors and fragrances. We conclude that blind subjects rely more on their sense of smell than the sighted in order to assess their environment and to recognize places and other people.