Mitigating cue competition effects in human category learning.

When people learn perceptual categories, if one feature makes it easy to determine the category membership, learning about other features can be reduced. In three experiments, we asked whether this cue competition effect could be fully eradicated with simple instructions. For this purpose, in a pilot experiment, we adapted a classical overshadowing paradigm into a human category learning task. Unlike previous reports, we demonstrate a robust cue competition effect with human learners. In Experiments 1 and 2, we created a new warning condition that aimed at eradicating the cue competition effect through top-down instructions. With a medium-size overshadowing effect, Experiment 1 shows a weak mitigation of the overshadowing effect. We replaced the stimuli in Experiment 2 to obtain a larger overshadowing effect and showed a larger warning effect. Nevertheless, the overshadowing effect could not be fully eradicated. These experiments suggest that cue competition effects can be a stubborn roadblock in human category learning. Theoretical and practical implications are discussed.