reward at the opposite end of the maze will demonstrate extinction learning when the food reward is later withdrawn, and extinction learning will be expressed behaviorally as a suppression of the original running approach response. Decrements of the original behavior constitute the most commonly cited outcome of extinction training and serve as the dominant measure of extinction learning and memory in most studies.

In the first half of the 20th century, extinction was interpreted in the context of learning theory, which at the time was dominated by two opposing viewpoints: the stimulus-response (S-R) view and the cognitive view. Clark L. Hull, who provided the most complete iteration of the S-R view at this time, suggested that initial acquisition of a memory may be likened to an acquired reflex, tocover the open access fee.

[^1]: Edited by: Michael A. Yassa, University of California, Irvine, United States

[^2]: Reviewed by: José M. Delgado-Garcìa, Universidad Pablo de Olavide, Spain; Marco Cambiaghi, Columbia University, United States
