More similar than you might think:
According to a spate of recent studies, our noses are in fact exquisitely sensitive instruments that guide our everyday life to a surprising extent. Subtle smells can change your mood, behaviour and the choices you make, often without you even realising it. Our own scents, meanwhile, flag up emotional states such as fear or sadness to those around us. The big mystery is why we aren't aware of our nasal activity for more of the time.
An explanation for why a smell can conjure up a vivid memory:
[T]he very first time we associate a smell with an object, it evokes a much greater response in our brains than for any subsequent encounter with the smell or object, laying down stronger foundations for the memory. That doesn't happen with any other sense. Since those first encounters with a smell would have happened at a young age, this might explain why smells often transport us back to our childhood.
The Dish 