Evidence for feature and location learning in human visual perceptual learning

In Experiment 1, human participants were pre-exposed to two similar checkerboard grids (AX and X) in alternation, and to a third grid (BX) in a separate block of trials. In a subsequent test, the unique feature A was better detected than the feature B when they were presented in the same location during the pre-exposure and test phases. However, when the locations of the features were swapped during the test (A was tested in the location occupied by B during pre-exposure and vice versa), B was detected better than A, suggesting that intermixed pre-exposure enhances the attention paid to the location of the unique features rather than the features themselves. In Experiment 2, participants were given intermixed or blocked pre-exposure to AX and X, and were then required to detect the differences between pairs of stimuli containing either the pre-exposed unique feature A or a new feature, N, presented in a familiar location (used for pre-exposure) or a new location within the checkerboard grid. Participants that were given intermixed pre-exposure showed a facilitated capacity to detect A than N, and detected better the unique features in the familiar than in the new location. In contrast, participants in the blocked condition did not show any effect of feature or location. These results provide evidence that both location and feature learning processes take place during intermixed (but not blocked) pre-exposure.