Speeded classification in simultaneous masking

In simultaneous masking, flanking elements impair performance on a visual target. Previous studies on simultaneous masking have predominantly used discrimination threshold estimation to quantify performance on the target. Results based on thresholds suggest that an important factor in simultaneous masking is the strength of grouping between the target and the flankers. Recently Panis and Hermens (2014) showed that error rates in a speeded discrimination task, using the same simultaneous masking paradigm, provide a very similar pattern of results compared to thresholds from previous studies. In contrast, response times were found to deviate from the pattern in the error rates in some of the conditions, possibly providing a method to tap into low-level visual processes within the same paradigm. However, only a small number of masks was used, and it is therefore unclear to what extent differences can be found between thresholds, error rates, and response times. Here, we address this issue by examining speeded classification performance on a vernier target for a broad range of simultaneous mask layouts. Results suggest that thresholds and error rates are strongly associated, and that response times generally show the same pattern of results, although to a slightly weaker extent. We suggest that masking strength, defined by either measure, appears to be linked to target-flanker grouping rather than to low-level interactions.