A Feynman propagator is constructed for the effective interaction between electrons which takes into account the polarizability of the medium of unexcited particles in the Fermi sea.
To put it simply, a smell made you remember something from your past, and it happened because of the way smells and memories are hard-wired into your brain.
There's something at the size of the model interacting with the kind of information that's in there and the chat method that has made them much more useful suddenly. It's a radical change in a very short period of time.