Figure 9. Behavioral change-detection experiment. A, Trial structure of the experiment. Subjects studied a set of six sample face images, followed by masks generated from scrambled face images. The subjects' task was to remember all six faces during the following brief delay. After the delay, a single probe face was presented at one of the six locations, and subjects indicated whether or not the probe face matched the sample face that had been studied at that location. B, Example pairs of sample and probe faces with high (top row), medium (middle row), and low (bottom row) eigenface score similarity. The z-scored Euclidean distances between the eigenface scores were −2.23, 0.01, and 2.72, respectively. C, Logistic regression testing for the relationship between the probability of making a “match” response on nonmatch trials and eigenface score similarity between the sample and probe faces. The numbers of correct and incorrect trials were controlled to be identical within each subject. Each dot indicates a single trial in the nonmatch condition, and trials from all subjects are shown. A value of 1 on the y-axis represents a “match” response, and a value of 0 represents a “nonmatch” response. Smaller values on the x-axis represent higher similarity (lower Euclidean distance) between the faces. Solid line indicates the fitted logistic regression line. The shaded area represents 95% bootstrapping confidence intervals. **p < 0.01.