Our five senses are gathering information at all times. One way our brain sorts the abundance of information is by combining information from two or more senses, such as between smells and the smoothness of textures, or pitch, color, and musical dimensions.
It may be why we began to associate higher temperatures with warmer colors, lower sound pitches with less elevated positions, or colors with the flavor of particular foods.
A new paper argues that such unconscious 'crossmodal' associations with our sense of smell can even affect our perception of colors.