Results of Experiment 1.

Accuracy (% of correct answers) is higher for high magnitude levels of contrast, frequency and FoV at 45% sp (“less than half” answers), while at 55% sp (“more than half” answers) it is always higher for low magnitude levels of contrast and frequency. At 45% sp, overestimation (incorrect responses, “more than half” answers) occurs more frequently for low magnitude levels. At 55% sp, underestimation (incorrect responses, “less than half” answers) occurs more frequently at high magnitude levels.