Which sense is most strongly tied to memory?

Smell has a shortcut the other senses do not. Sight, sound and touch are all routed through the thalamus, which acts as a relay station, before reaching the parts of the brain that handle memory and emotion. Smell goes almost directly into the olfactory bulb, which sits next door to the amygdala and hippocampus - the structures that handle emotion and the laying down of memory.

That anatomy is why a smell can produce a memory that arrives whole and unbidden, complete with the feeling attached, rather than the reconstructed version you get by trying to remember something on purpose. The effect is named after Proust, whose narrator is knocked sideways by a madeleine dipped in tea - though in the novel it is really the taste, and taste is mostly smell anyway.

It is also the sense people underrate most and lose most easily. Losing it is an early sign in Parkinson's and Alzheimer's disease, and became a familiar symptom in 2020. People who lose it often report the loss of appetite and a peculiar kind of grief, because the past stops arriving unannounced.