Experimental design.

<p>Note: A/A* to E/E* represent pairs of difficult to discriminate stimuli. A within-subjects factorial design was used that manipulated exposure type (intermixed, blocked, and control) and stimulus type (dots, faces, scenes). Each presented image was shown 5 times for 2 seconds each with a 1 second ISI. After an exposure stage (A/A* and B/B* intermixed, C/C* and D/D* blocked), participants received a same/different test phase in which the exposed stimuli and two novel pairs of stimuli (E/E* and F/F*) were presented. This design was repeated six times (twice each with dots, faces, or scenes) with different stimuli as A–F.