Identifying odors within mixtures is a difficult task: humans are able to recognize only up to 4 odors within a mixture. We wanted to test the effects of olfactory training on this ability. We used 7 odorants to create 35 olfactory stimuli of 1, 2, 3, 4, or 5 odorants. The task consisted of identifying the odorants present within the mixture. We trained novices on this task for 5 days: they came to the laboratory to perform the task once a day before coming back for the final testing. Then, we compared them to sommeliers, thus olfaction experts, and untrained novices. Results showed that sommeliers outperformed the other groups with mixtures of up to 4 odorants but not with mixtures of 5 odorants. The short olfactory training allowed trained participants to perform as well as sommeliers when it came to identifying single odorants but was not enough to improve their performance when stimuli were mixtures of 2 or more odorants. This study supports the idea that the number of odors we can recognize within a mixture is limited but suggests training can improve the performance: a short olfactory training is enough to enhance the ability to identify single odorants, whereas expertise refines identification ability of mixtures of up to 4 odorants.

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