Individual differences in metacontrast masking: A call for caution when interpreting group data

Replies to a comment by T. Bachmann (same issue) on a study by T. Albrecht, S. Klaptöke, and U. Mattler (same issue) on individual differences in metacontrast masking. In this study, it was found that perceptual learning enhanced 2 groups of observers with qualitative individual differences in metacontrast masking. The issues raised included initial similarities and differences in Type A and Type B observers, whether the results can be attributed to a difference in direct phenomenal experience or in criteria, and an emphasis on the importance of individual data. It is indicated that the observers were similar at the beginning of each experiment, and that further research is needed in order to locate the source of the observed individual differences and to determine what the groups have in common and where they differ. Furthermore, it is argued that the observers were not able to choose which feature they used, and that perceptual learning either improves conscious perception or the use of criteria. Finally, the importance of the data of individual participants in experimental psychology is highlighted.

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