Brain Research Bulletin 84 (2011) 206–209 Contents lists available at ScienceDirect Brain Research Bulletin journal homepage: www.elsevier.com/locate/brainresbull Research report Odor perception and odor awareness in congenital blindness Mathilde Beaulieu-Lefebvre a,b , Fabien C. Schneider c,d , Ron Kupers e,∗ , Maurice Ptito a a École d’Optométrie, Université de Montréal, Montréal, QC, Canada H3C 3J7 b Department of Psychology, University of Montreal, Montreal, Canada H3C 3J7 c Radiology Department, Hospital of Saint-Etienne, University of Saint- Etienne, Jean Monnet, France d Centre de Neurosciences Cognitives UMR 5229, Bron, France e Institute of Neuroscience and Pharmacology, Panum Institute, University of Copenhagen, Copenhagen, Denmark article info Article history: Received 16 August 2010 Received in revised form 21 December 2010 Accepted 26 December 2010 Available online 12 January 2011 Key words: Blindness Olfaction Odor awareness Detection threshold Crossmodal plasticity abstract 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 dis- crimination 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. © 2011 Elsevier Inc. All rights reserved. 1. Introduction Despite the lack of visual input, congenitally blind subjects are able to find their way around, assess objects and their impor- tance, cook, read, and recognize their friends and kins. In short, they are well aware of their immediate environment. It is generally acknowledged that blind individuals develop supra-normal sen- sory abilities in their remaining senses in order to compensate for their visual deficit. Studies on auditory and tactile modalities sup- port this sensory advantage attributed to the blind. Several studies have indeed shown superior performance of the blind in tactile discrimination [1,5,13,15,35,39,42], sound localization and pitch discrimination [9,7,12,17,18,20,26,29–31,40,41]. In sharp contrast with the wealth of studies on tactile and audi- tory processing in the blind, little is known about their sense of smell. A Pubmed search of the literature listed only 10 published articles on the topic between 1889 and 2010 and with rather contradictory results. On the one hand, Griesbach (1889; cited in Smith et al. [37]) and Cherubino and Salis [6] and Boccuzzi [3] found no differences between the olfactory abilities of blind and ∗ Corresponding author at: Institute for Neuroscience and Pharmacology, Panum Institute, Faculty of Health Sciences, University of Copenhagen, Blegdamsvej 3B, 2200 Copenhagen, Denmark. Tel.: +45 35456890; fax: +45 35453989. E-mail address: ron@pet.rh.dk (R. Kupers). sighted subjects, whereas Mahner (1909) and Bertoloni (1942) (both cited in [37]) concluded that congenitally blind individuals have a more developed sense of smell. In addition, Murphy and Cain [25] reported that although the odor detection threshold was poorer for the blind, they could name 31% more familiar odors than a sighted control group. More recent and better-controlled studies on olfaction in the blind also produced some contradic- tory results. For instance, whereas a study by Smith et al. [37] showed that blind people (congenital and late onset) are not bet- ter at detecting, discriminating or identifying odors, Cuevas et al. [8] reported increased odor discrimination and odor identification. Also, Rosenbluth et al. [34] found that congenitally blind children are better and faster in a free identification of odors paradigm but not when using a multiple-choice paradigm, suggesting superior verbal abilities rather than enhanced perceptual abilities. One of the possible reasons for the discrepancy in results is that these studies did not standardize olfactory testing procedures. In fact, an eclectic assortment of testing procedures was used in the experi- ments cited above, ranging from home-made dilutions or odorant items from household placed in plastic bottles, to validated tests such as the University of Pennsylvania Smell Test [11] and the Sniffin’Sticks test [19]. With such diversity in testing procedures, it may not come as a surprise that the outcomes of the differ- ent studies lack congruity. Moreover, the clinical tests used may not have the power to discriminate normal from supranormal performance. 0361-9230/$ – see front matter © 2011 Elsevier Inc. All rights reserved. doi:10.1016/j.brainresbull.2010.12.014