Contiguity theory or law of contiguity was introduced by American philosopher, mathematician and psychologist Edwin Gurthie. It emphasizes that the only necessary condition for the association of a stimulus with a response is a close temporal relationship between the two.

Gurthie attempted to explain learning through association of stimuli with responses. All learning, according to Gurthie, was a consequence of associating a particular stimulus with a particular response. This association will only occur if stimuli and responses occur soon enough one after another (contiguity law). The association is established on the first experienced instance of the stimulus. Repetitions or reinforcement do not influence the strength of this connection. This was according to Gurthie the only type of learning.