Simultaneous completions of modal and amodal figures: Visual evoked potentials reveal asymmetrical interference effects |
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| Authors: | Mathieu Brodeur Franco Lepore Benoit A. Bacon |
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| Affiliation: | 1. Douglas Mental Health University Institute , McGill University;2. Research Centre in Neuropsychology and Cognition , University of Montreal , Montreal, Canada;3. Research Centre in Neuropsychology and Cognition , University of Montreal , Montreal, Canada;4. Research Centre in Neuropsychology and Cognition , University of Montreal , Montreal;5. Department of Psychology , Bishop's University , Sherbrooke, Canada |
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| Abstract: | Modal and amodal completion processes are thought to affect the emergence and the potency of each other. To see whether one dominates over the other, we measured the Npd, that is, the negativity of visual-evoked potentials whose amplitude increases with perceptual difficulty. In the first experiment, the Npds to illusory (modal) squares and diamonds placed over amodal diamonds and squares, respectively, were found to be greater when targets were the amodal figures than when targets were the modal figures, thus suggesting that modal figures created more interference. A second experiment showed that greater Npds were specific to interference and not to the greater difficulty at focusing on amodal figures rather than on modal figures. A third experiment showed that the interference also occurs with real figures in replacement of modal ones. Overall, the results suggest a certain dominance of modal completion over amodal completion when both occur in the same display. |
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