Our sense of smell changes the colours we see: Study

NEW DELHI: Unconscious associations with our sense of smell or odour can even affect our perception of colours, finds a new study.

The researchers now emphasise the need to investigate how far-reaching such “crossmodal” associations between odours and colours are.

“Here we show that the presence of different odours influences how humans perceive colour,” said lead author Dr Ryan Ward, a senior lecturer at Liverpool John Moores University in Liverpool, UK.

One way our brain makes sense of an abundance of information is by combining information from two or more senses, such as between smells and the smoothness of textures, pitch, colour, and musical dimensions.

This sensory integration also causes us to associate higher temperatures with warmer colours, lower sound pitches with less elevated positions, and colours with the flavuor of particular foods – for example, the taste of oranges with the colour of the same name.

Now, a study in Frontiers in Psychology has shown experimentally that such unconscious 'crossmodal' associations with our sense of smell can affect our perception of colours.

Ward and colleagues tested for the existence and strength of odour-coloor associations in 24 adult women and men between 20 and 57 years of age.

The participants were seated in front of a screen in a room devoid of unwanted sensory stimuli for the duration of the experiments.

They wore no deodorants or perfumes, and none reported being colour-blind or having an impaired sense of smell.

All ambient odours in the isolation room were purged with an air purifier for four minutes.

Then one of six odours (chosen at random from caramel, cherry, coffee, lemon, and peppermint, plus oduorless water as a control) was broadcast into the room with an ultrasonic diffuser for five minutes.

“In a previous study, we had shown that the odour of caramel commonly constitutes a ‘crossmodal’ association with dark brown and yellow, just like coffee with dark brown and red, cherry with pink, red, and purple, peppermint with green and blue, and lemon with yellow, green, and pink,” explained Ward.

The results showed that participants had a weak but significant tendency to adjust one or both of the sliders too far away from neutral grey.

For example, when presented with the odour of coffee, they wrongly perceived ‘grey’ to be more of a red-brown colour than true neutral grey.

“These results show that the perception of grey tended towards their anticipated crossmodal correspondences for four out of five scents, namely lemon, caramel, cherry, and coffee,” said Ward.

“We need to know the degree to which odours influence colour perception,” the authors wrote.