Figure 1

Test of memory for order with the decline-test option. After touching the green ready square to initiate a trial, monkeys saw and touched a list of five images in sequence. On two-thirds of trials, monkeys were given the option to accept or decline the memory test. If the test was accepted, monkeys were reinforced for selecting from two images the one that had occurred first in the study list. Images from the study list were not responsive to touch until the monkeys selected the accept-test symbol (check mark icon), after which monkeys could complete the memory test and receive a comparatively large reward of two pellets if correct. Errors resulted in no reward and a time-out during which the screen was blank. Selecting the decline-test option (thumbs down icon) resulted in escape from the test, followed by a smaller guaranteed reward of one pellet. On one-third of trials only the accept-test option, forcing monkeys to take the memory test.