In the first stage of Experiments 1-3, subjects learned to associate different geometrical figures with colors or with verbal labels. Performance in Stage 2, in which the figures signaled which of 2 motor responses should be performed, was superior in subjects required to make the same response to figures that had shared the same Stage 1 associate. A third stage of testing showed that the events used as associates in Stage 1 were capable of evoking the motor response trained in Stage 2, an outcome predicted by an associative interpretation of such transfer effects. Experiment 4 provided evidence that the relevant associations can be effective in controlling motor responding even when subjects report an antagonistic relationship between events.

The effect of preexposure on human perceptual learning was investigated in four experiments. In Experiments 1a and 1b, participants were preexposed to one pair of visual stimuli on an intermixed schedule (AX/BX) and one on a blocked schedule (CX_DX). The ability to discriminate between AX and BX and between CX and DX was then assessed by examining the extent to which key presses assigned to each member of a stimulus pair generalized to the other member (Experiment 1a) and by looking at the accuracy of same-different responses (Experiment 1b). Stimuli were more easily discriminated following intermixed than following blocked preexposure on both the generalization and same-different tasks. This suggests that two stimuli are more perceptually distinct after intermixed preexposure. Experiments 2a and 2b investigated the mechanisms responsible for perceptual learning using same-different tasks. The results support the suggestion that the enhanced discrimination observed after intermixed preexposure is due to increases in the salience of the unique elements.

Assessment and treatment for hepatitis C virus (HCV) in the community remains low. We evaluated factors associated with HCV specialist assessment and treatment in a cross-sectional study to evaluate treatment considerations in a sample of 634 participants with self-reported HCV infection in New South Wales, Australia. Participants having received HCV specialist assessment (n = 294, 46%) were more likely to be have been older (vs <35 years; 35-44 OR 1.64, P = 0.117; 45-54 OR 2.00, P = 0.024; ≥55 OR 5.43, P = 0.002), have greater social support (vs low; medium OR 3.07, P = 0.004; high OR 4.31, P < 0.001), HCV-related/attributed symptoms (vs none; 1-10 OR 3.89, P = 0.032; 10-21 OR 5.01, P = 0.010), a diagnosis of cirrhosis (OR 2.40, P = 0.030), have asked for treatment information (OR 1.91, P = 0.020), have greater HCV knowledge (OR 2.49, P = 0.001), have been told by a doctor to go onto treatment (OR 3.00, P < 0.001), and less likely to be receiving opiate substitution therapy (OR 0.10, P < 0.001) and never to have seen a general practitioner (OR 0.24, P < 0.001). Participants having received HCV treatment (n = 154, 24%) were more likely to have greater fibrosis (vs no biopsy; none/minimal OR 3.45, P = 0.001; moderate OR 11.47, P < 0.001; severe, OR 19.51, P < 0.001), greater HCV knowledge (OR 2.57; P = 0.004), know someone who has died from HCV (OR 2.57, P = 0.004), been told by a doctor to go onto treatment (OR 3.49, P < 0.001), were less likely to have been female (OR 0.39, P = 0.002), have recently injected (OR 0.42, P = 0.002) and be receiving opiate substitution therapy (OR 0.22, P < 0.001). These data identify modifiable patient-, provider- and systems-level barriers associated with HCV assessment and treatment in the community that could be addressed by targeted interventions.

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.