ABSTRACT
A smell always stimulates the same receptors except for minor differences in left-right intensity, immediately revealing the familiarity and desirability (or otherwise) of its source. Smells can be detected at a distance, which makes them useful for guiding locomotion. The olfactory sense is less useful for supervising manipulatory responses. For that, animals without vision use mainly tactual receptors of the face and mouth and, in some cases, paws.
