Figure 3.

Probability of declining tests on normal trials and on probe trials lacking an image to study. Dark bars show the proportion of normal trials in which monkeys declined tests; the light bars represent this proportion in probe trials. Error bars are standard errors. Inset in each bar is the percent of each test type declined only in the first session of testing. These results indicate that it is the absence of a memory that causes the monkeys to decline tests. If some factor other than the absence of memory per se, such as distracting noises, variation in motivation, or fatigue, controlled the decision to decline tests, normal and probe trials would be affected equally.