In the Skinner Box:

Phase 1: The electric shock turns on. The rat presses the bar and the shock goes off immediately.

Phase 2: After phase 1, the electric shock turns on. The rat presses the bar, but the shock stays on.

What is phase 1?

Escape training/conditioning.

Explanation:

The Skinner box or operant conditioning chamber is a laboratory system created to study animal behavior by American psychologist B. F. Skinner (March 20, 1904 - August 18, 1990).

It has a mechanism that conditions animal behaviour by subsequent introduction of reward or punishment. In this example, the rat is conditioned or in other wards is trained to escape punishment in the form of the electric shock by pressing the bar.