Noise masking analysis of facial expression perception C-C Chen |
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Department of Psychology, National Taiwan University, Taiwan
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| We used a noise masking paradigm to investigate the facial expression detection mechanisms. The targets were pictures of faces with happy, sad, fearful, angry or neutral expression. The masks were random dot patterns. A 2AFC paradigm was used to measure target contrast threshold at 75% accuracy. In each trial, the noise was presented in both intervals and the target was in one interval. In the face detection (FD) conditions the non-target interval contained the phase-scrambled version of the target while in the expression detection (ED) conditions it contained a face of neutral expression. The observer was to indicate the target interval. In all conditions, the target threshold vs. masker contrast (TvC) functions were flat at low masker contrast and increased with masker contrast when the masker contrast was beyond a critical value. The thresholds for happy faces in both ED and FD conditions were the same at all noise level, suggesting happy might be the default expression. For other expressions, the ED contrast thresholds were more than 50% greater than the corresponding FD thresholds and the ED critical values were greater than the FD ones. The results suggest that the ED mechanisms are less sensitive to contrast than FD ones. |
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