Emotional Faces in Peripheral Crowding

Crowding effect refers to the deficit in identifying viewed targets, such as letters, numerals, line segments, or grating patches, when other shapes are nearby. This effect is reduced when distractors have a different color, contrast, or binocular disparity than that of the target. With feature singleton targets, the crowding effect decreases dramatically with an increasing number of distractors for both simple orientation and more complex letter identification tasks [4]. With a target that is not a salient feature singleton, however, the increasing number of distractors worsens rather than improves the perception of the target [2]. The present study uses the popular paradigm of crowding effect to explore whether the emotional schematic faces are salient in the peripheral visual field, and can affect the crowding effect by bottom-up salience of target. For the emotional faces have the ability of attention capture [1][3], we expected to see a normal crowding effect with the target crowding by a single ring of distractors, and performance would be recovered as the distractors increasing. In other words, if the positive or negative expression can ‘pop-out’ in the parafovea, we expect to see, with emotional singleton targets, the crowding effect may decrease even with an increasing number of distractors (neutral schematic faces). Three undergraduates (2 women and 1 man) were paid to participate in the experiment. Participants’ task was to judge the emotional face (either positive or negative expression) among neutral expression is red or green and press the corresponding key. A target was presented at a fixed eccentricity, 60 mm either to the left or to the right of the fixation point, which was at the centre of display (Fig. 1). From a viewing distance of approximately 57 cm, this eccentricity corresponded to 6 deg of visual angle. Distances (center to center) between rows and columns of objects were 16 mm. Distractors (if present) formed a square matrix comprising 1×1 (a target alone), 3×3, 5×5, or 7×7 objects with the target in the center. Examples of stimuli for experiment were given in Fig. 2A, B, and C. ANOVA of reaction times were conducted and the results showed that responses were fastest for no distractor condition (M = 255 ms,