birds flock together, fish school together, cattle herd together...just perceiving norms is enough to cause people to adjust their behaviour in the direction of the crowd.
2015年12月六级真题（第二套）阅读 Section B
柯林斯高阶英汉双解学习词典释义
VERB
注意到，察觉，意识到（尤指不明显之物）
If you perceive something, you see, notice, or realize it, especially when it is not obvious.