Abstract: Previous studies have demonstrated that humans use a variety of facial cues, including gaze direction and nose angle, to perceive the direction in which a crowd is looking. For example, in a study using simple line-drawing faces, Sweeny et al. (2014) argued that the visual system pools information from nose angle and pupil rotations at the group level to determine the focus of attention of a crowd. However, there is currently no consensus as to the relative importance of eyes and nose cues in determining the focus of attention. Furthermore, the relative importance of these cues may differ when perceiving individual faces compared to crowds. The purpose of the first experiment was to determine whether the ensemble perception of the focus of attention of based on more than one face.For investigating the process of perception, Experiment 2 used the eye tracker to explore differences in how the focus of attention is derived when looking at crowd vs individual people. In experiment 1, either an individual face or crowd of faces (two, three or four faces) were presented on a 14-inch Lenovo computer by E-prime 2.0. Ninety-six faces with various pupil rotations and head orientations were constructed by Autodesk Maya 2014 and Photoshop 5.0. Thirty undergraduate students were required to complete an averaging orientation judgement task in which they wereinstructedtoestimate where the individual’s face or crowd’s faces were looking. Experiment 2 was 2 (facial cues: eyes and nose) × 4 (number of faces) within-subject design. Thirty-four participants` eye movements were recorded with an SMI RED eyetracker(22-inch screen, sampling rate=250Hz, resolution=1024 ×768 pixels, refresh rate=60Hz, participants - and - screen distance=57-60cm). The results of experiment 1 showed that the accuracy of using multiple faces of the crowd to estimate the direction of crowd’s attention was significantly higher than that of using an individual’s face (p＜0.05＝, which indicated that observers integrated at least two faces to perceive crowd attention. The results of experiment 2 suggested that the way in which we estimate an individual’s attentional focus is distinct from how we estimate the focus of attention of a crowd. (1) For both individual and crowd of faces, the entry time of noses was significant lower than that of eyes, p＜0.05, (2) The first fixation duration of the noses on individual faces was longer than that of eyes, p＜0.01, whilefor the crowd of faces, there is no significant difference between the first fixation duration on the noses and eyes. (3) The probability of first fixation located on noses was higher than that of eyes in individual faces condition, p＜0.05, yet in two faces or four faces conditions, the probability of first fixation located on eyes was higher than that of noses, p＜0.01. (4) For individual faces, total fixation duration of noses was longer than that of eyes, p＜0.01, whereas for crowd faces, there is no difference between noses and eyes on total fixation duration. When determining the focus of individual’s attention through facial cues, nose is more important than eyes. While under crowd condition, both nose and eyes are equally important. The results indicated that the visual system pools the gazes of faces into an ensemble code based on both eyes and nose, which allows humans to rapidly and efficiently perceive where a crowd is looking.

Key words: crowd attention, ensemble coding, eye tracking

摘要： 探讨个体和群体注意方向判断中对面孔部件（眼睛和鼻子）的依赖程度。实验一使用不同数量面孔的图片，要求报告群体或个体的注意方向。发现多面孔条件下对群体注意方向估计的准确性高于单面孔条件。实验二采用眼动技术，讨眼睛和鼻子在判断其注意方向时注视的空间分布特征和时间进程规律。结果发现，单张面孔时，对鼻子的总注视时间长于眼睛；多张面孔时，二者没有差异。结果表明，知觉个体注意主要依赖鼻子，知觉群体注意依赖眼睛和鼻子。

关键词: 群体注意, 整体编码, 眼动追踪