The 'Gazette'
The sensory perception of a scent results from a rapid, even instantaneous stimulus that triggers a series of neurological and emotional reactions. This complex process can be broken down into three distinct levels: the chemical detection of odor molecules, their interpretation by the brain, and finally, the affective or memory-related response they evoke. In this article, we present these three stages in detail.
The qualitative perception is the recognition and identification of a smell, meaning what we associate it with. It therefore refers to our memory, but also our ability to name it.
The quantitative perception is the intensity of the smell. Different methods exist to quantify this intensity: the detection threshold and the recognition threshold (see below).
The hedonic or emotional perception refers to the pleasant or unpleasant character of a smell: the famous “I like” or “dislike it”. However, a pleasant smell may become unpleasant at very high concentrations.
They reflect the strength of a smell and vary depending on the odorous molecules, the complexity of the mixture, but also between individuals. For an odorous molecule, a distinction is made between:
– The detection threshold: which refers to the concentration at which there is a 50% chance of detecting the odour but without being able to describe it.
– The recognition threshold: which is higher than the perception threshold and is the concentration at which the odour can be described.
The mixture of several odorous molecules may lead to perceptive interactions, with changes in both the nature of the smell and its intensity. If the two molecules have very different smells and volatilities, they will both be perceived. However, if the volatilities are similar, it is possible to create a new smell in precise proportions, called “an accord ” by perfumers. In the next article, we’ll look at the types of mixtures and how they smell.
Richardson, J. T., & Zucco, G. M. (1989). Cognition and olfaction: a review. Psychological bulletin, 105(3), 352
Patte, F., Etcheto, M., & Laffort, P. (1975). Selected and standardized values of suprathreshold odor intensities for 110 substances. Chemical Senses & Flavor
R&D | March 2025 | Dr. Magali Picard