Individual differences in metacontrast masking regarding sensitivity and response bias

In metacontrast masking target visibility is modulated by the time until a masking stimulus appears. The effect of this temporal delay differs across participants in such a way that individual human observers’ performance shows distinguishable types of masking functions which remain largely unchanged for months. Here we examined whether individual differences in masking functions depend on different response criteria in addition to differences in discrimination sensitivity. To this end we reanalyzed previously published data and conducted a new experiment for further data analyses. Our analyses demonstrate that a distinction of masking functions based on the type of masking stimulus is superior to a distinction based on the target–mask congruency. Individually different masking functions are based on individual differences in discrimination sensitivities and in response criteria. Results suggest that individual differences in metacontrast masking result from individually different criterion contents.

► Different observers exhibit qualitative different types of masking functions.
► The congruency between target shape and mask shape apparently affects target discrimination.
► These congruency effects reflect response bias rather than discrimination sensitivity.
► Observers differ in discrimination sensitivity and response bias.
► Differences in response bias indicate the use of different perceptual cues.