Eva was very stressed and feeling constant anxiety. recently she discovered an on-line game of tetris, and soon she was playing for hours a day. while eva plays tetris, her anxiety is removed, or at least out of her awareness, and when she stops, the anxiety returns. thus, eva has learned to play tetris through the mechanism

Negative reinforcement

Explanation:

In psychology, negative reinforcement is a type of classical conditioning and therefore, a type of learning by which the individual strengths a certain behavior by removing a negative stimuli that occurs when the behavior is not taking place.

In this example, Eva is feeling constant anxiety but she starts playing Tetris and her anxiety is removed and when she stops, it comes back. The playing of Tetris is being reinforced because it helps Eva remove a negative stimulus (the anxiety) that occurs when she is not playing. Therefore, she ends up playing Tetris through the mechanism of negative reinforcement.