They also sat in front of a screen filled with a random color, whilst an ultrasonic diffuser pumped one of six odors into the room – caramel, cherry, coffee, lemon, peppermint, or water as a control – for five minutes. Using two sliders, participants were then asked to manually adjust the color on the screen to what they perceived to be true neutral gray.

The study found that people had a weak but significant tendency to shift the color too far away from neutral gray, in different but predictable ways depending on the scent – except for peppermint. The smell of coffee made participants perceive gray as a more red-brown color, whilst caramel led to more of a yellow-brown. To be expected given their respective dullness, odorless water corresponded to true neutral gray.

– Read more in Our Sense Of Smell Changes How We See Color at IFLScience.