Metacontrast suppression and criterion content: A discriminant function analysis

Three test and three mask energies of a metacontrast display were varied orthogonally and randomly over trials. The stimulus onset asynchrony (SOA) separating them was varied over blocks of trials from 0 to 180 msec in 30-msec steps. Both the accuracy in judging the test and the coherence (consistency) of the judgments were U-shaped functions of SOA. Thus, metacontrast suppression is in part due to inadequate information. In addition, mask energy was found to correlate negatively with judgments of the test at short SO As but positively at longer SOAs. This indicates that part of the masking effect is due to inappropriate use of information. Certain similarities were noted between these findings and those obtained with judgments of frequency in the auditory-recognition masking paradigm. In general, the results indicate that subjects respond to different features of the stimulus situation as SOA varies.