Smell and Color

Crossmodal association (or crossmodal perception, integration, or plasticity, depending on who's doing the research) refers to our tendency to blend perceptual data generated by our hearing, smelling, tasting, touching, and seeing apparatuses.

Synesthesia, which is the stimulation of one sense-associated brain pathway by an unrelated bit of sensory information (a color making us hear a sound, or a sound making us taste something, for instance) is a fairly well-known example of this, but there are also more obscure examples like the McGurk Effect, which involves perceiving a novel sound when the auditory component of an action is replaced with a different sound (if we see someone say "ga ga" but hear subbed-in audio that says "ba ba," we may think we heard something else entirely).

In both cases, our brains are trying to make sense of something we're perceiving, but either getting its wires crossed or inaccurately filling in blanks, which to the perceiver can be a disorienting or even disturbing experience, as our realities are shaped in part by the sensory information we collect and parse; so what we consider to be "real" and "true" can be distorted, in turn warping our intuitive understanding of tangible reality.