The subjects also looked at a neutral image of a familiar person, such as a classmate or friend of a friend.
受访者们也看到了一个普通的熟人的照片，比如一个同学或者朋友。
2
The researchers prompted subjects to have a relaxed, neutral facial expression for both pictures.
研究者还要求志愿者在两幅照片里都摆出放松、中性的表情。
3
They recruited six hundred subjects, most of them undergraduates, and had them perform a variety of basic cognitive tests displayed against red, blue or neutral colored backgrounds.