The effect of additional exposure to the unique features in a perceptual learning task can be attributed to a location bias

It has been suggested that human perceptual learning could be explained in terms of a better memory encoding of the unique features during intermixed exposure. However, it is possible that a location bias could play a relevant role in explaining previous results of perceptual learning studies using complex visual stimuli. If this were the case, the only relevant feature would be the location, rather than the content, of the unique features. To further explore this possibility, we attempted to replicate the results of Lavis, Kadib, Mitchell, and Hall (2011, Experiment 2), which showed that additional exposure to the unique elements resulted in better discrimination than simple intermixed exposure. We manipulated the location of the unique elements during the additional exposure. In one experiment, they were located in the same position as that when presented together with the common element. In another experiment, the unique elements were located in the center of the screen, regardless of where they were located together with the common element. Our results showed that additional exposure only improved discrimination when the unique elements were presented in the same position as when they were presented together with the common element. The results reported here do not provide support for the explanation of the effects of additional exposure of the unique elements in terms of a better memory encoding and instead suggest an explanation in terms of location bias