“…Similar evidence comes from studies with animals, which exhibit poor performance when the environmental context is modified between training and testing. Such alterations of the context may concern external stimuli, change of experimental room (Gordon, McCracken, Dess-Beech, & Mowrer, 1981), slight modifications of the training apparatus (Perkins & Weyant, 1958;W. R. McAllister & D. E. McAllister, 1963), or internal stimuli, such as changes in the internal state of the animal following injections of drugs (cf.…”