In Experiment 1a, participants were exposed, over a series of trials, to separate presentations of 2 similar checkerboard stimuli, AX and BX (where X represents a common background). In one group, AX and BX were presented on alternating trials (intermixed), in another, they were presented in separate blocks of trials (blocked). The intermixed group performed to a higher standard than the blocked group on a same-different test. A superiority of intermixed over blocked exposure was also evident in a within-subject design (Experiment 1b) and when the test required discrimination between a preexposed stimulus and the background (e.g., AX vs. X), even if the background changed between preexposure and test (AY vs. Y) (Experiment 2). In Experiment 3, the intermixed/blocked effect was observed when, in preexposure, stimulus presentations were alternated with the background alone (e.g., AX/X). This suggests that the perceptual learning effect is not the consequence of inhibitory associations between unique features but to increased salience of those features. Experiment 4 confirmed this finding and also ruled out an account of the effect in terms of trial spacing.

A robust finding in humans and animals is that intermixed exposure to 2 similar stimuli (AX/BX) results in better discriminability of those stimuli on test than does exposure to 2 equally similar stimuli in 2 separate blocks (CX_DX)--the intermixed-blocked effect. This intermixed-blocked effect may be an example of the superiority of spaced over massed practice; in the intermixed, but not the blocked exposure regime, each presentation of a given stimulus (e.g., AX) is separated from the next by the presentation of its partner (BX). Two experiments with human participants replicated the intermixed-blocked effect and showed that the effect was not due to the spacing of exposure trials. A mechanism for the intermixed-blocked effect is proposed, which combines theories from associative learning and memory.

Individuals with Alzheimer's disease (AD) experience difficulties with socioemotional functioning, and it has been proposed that cognitive disinhibition may be one potential mechanism that contributes to difficulties in this area. To test this possibility, twenty individuals with AD and 20 demographically matched controls were administered self-report measures of depression, emotion regulation and empathy, in addition to a behavioral measure that has proven to be very sensitive to inhibitory failures (the Hayling Sentence Completion Test). Relative to controls AD participants exhibited increased inhibitory failures on the Hayling, and self-reported significantly reduced cognitive empathy, but did not differ with respect to affective empathy, depression or perceived capacity for emotion regulation. Controlling for general cognitive status, in the AD (but not the control) group, reduced cognitive inhibition was associated with lower levels of depression. The theoretical and practical implications of these results are discussed. (JINS, 2007(JINS, , 13, 1060(JINS, -1064