Smell

Olfaction, also known as smelling, was a method of detecting chemicals. Different types of creatures used different organs to smell; humans used the lining of their noses, insects used their antennae and Myxilinic frost-worms smelled from above the central mouth. (TDL: The Colour of Darkness) Though similar to a Human's, the Gallifreyans could do a chemical analysis of the air using their sense of smell. (DWN: Doctor Who and the Carnival of Monsters)

In many species, like Humans, the olfactory system used the same parts of the brain as memory and emotion. This was a weakness that the Dreamspinner, Shas-Raklat, exploited by changing the Karagulan's perception of events in order to abduct their children for spare sensory parts. (TDL: The Colour of Darkness)