Jerzy Konorski was a Polish neurophysiologist who further developed the work of Ivan Pavlov by discovering secondary conditioned reflexes and operant conditioning. He also proposed the idea of gnostic neurons, a concept similar to the grandmother cell. He coined the term neural plasticity, and he developed theoretical ideas regarding it that are similar to those proposed soon after by Donald Hebb.

Operant conditioning, also called instrumental conditioning, is a learning process where voluntary behaviors are modified by association with the addition of reward or aversive stimuli. The frequency or duration of the behavior may increase through reinforcement or decrease through punishment or extinction.