We've all experienced it: Suddenly, you catch a whiff of something and you're instantly transported to some time and place from months, years, or even decades in the past. No other sense has such power, and the reason is straightforward: Scents have a direct connection to the parts of your brain responsible for memory and emotion.
Every other sensation – sight and sound, for example – must first find their way to the thalamus, which acts like a way station and sends them on to another part of the brain.
Rachel Herz, an adjunct assistant professor of psychiatry and human behavior at Brown University, says that because scents go directly to the emotion-focused amygdala and the memory-holding hippocampus, they are "experienced as more emotional and more evocative."
Herz believes that this special quality of smell probably has an evolutionary basis. "Emotions tell us about approaching things and avoiding things, and that's exactly what the sense of smell does too," she said. "So, they're both very intimately connected to our survival."
The nose knows:
- A Rockefeller University study determined that people can detect about a trillion different scents.
- While people have up to 6 million cells that detect smells, dogs have 220 million.
- As with fingerprints, every person's odor identity is unique.