Making sense of scents: the colour and texture of odours.

The purpose of this study was to document colour and texture associations to odours using a variety of odours including both pleasant and unpleasant odours, some of which were likely to be unfamiliar. We asked non-synaesthetic adults (n = 78) to make colour and shape/texture associations to 22 odours. A subset of the participants (n = 41) smelled the odours a second time in order to identify them. Each odour stimulus was associated consistently to one or more specific colours and/or textures (all p's < 0.01 by binomial probability statistics). Associations to the four odours that were identified accurately (cinnamon, lemon, peppermint and licorice) seemed to be based on learning/memory (e.g. lemon = yellow). The associations to the 18 odours that were not identified accurately are less likely to be based on learning/memory (e.g. ginger = black, rough, sharp; lavender = green, white, liquid, sticky). We speculate that sensory associations to odours, like those to pitch and letters (e.g. Mondloch and Maurer, 2004; Spector and Maurer, 2008), may result from the joint influence of learning and natural biases linking dimensions across sensory systems. Such links may reflect inherent neural organization that is modifiable with learning and that can manifest as cross-modal associations or synaesthetic percepts.