Temporal competition between odorants: effect of different time intervals on the perception of monorhinic and dichorhinic binary mixtures.

Backward masking and its possible connection with the perception of odour mixtures has been investigated. Temporal competition between odorants in a binary mixture was tested by artificially creating a delay between one odour (the target) and a second, stronger, odour (the mask) during a single natural sniff. To test the influence of central versus peripheral competition, the same mixture was presented either monorhinically or dichorhinically. The delay (100 to 400 ms) did not influence intensity perception, indicating that intensities are integrated during the sniff irrespective of the temporal arrangement. In contrast, the number of qualities perceived was influenced by the delay: delays of 200 to 400 ms gave significant increases in the frequency of detection of a mixture, whereas synchronous mixtures favoured the perception of a single odour. Masking was also significantly stronger in dichorhinic mixtures. These effects are discussed in terms of retroactive masking which seems to be enhanced by dichorhinic mixtures, suggesting that masking has an important central component.