Two researchers at University of Toronto demonstrated that people can accurately identify if a face belongs to a rich or poor individual.
Interestingly, it seems that this ability relies on both accurate cues (such as health and well being) and stereotypes (such as attractiveness and intelligence)--and is more developed in women than men.
The 81 undergraduate students recruited to take part in this study succeeded in identifying the social class of 160 faces 61% of the time (well above chance level.)
What is more, in a follow-up study, subjects managed to do so 58% of the time based on a cropped mouth alone (versus 52% based on cropped eyes.)
Finally, the researchers pointed out that, although this phenomenon might lead to self-fulfilling prophecies, actively engaging in emotional expression obscures the subtle cues people use to infer each other’s social class
Sources: Bjornsdottir and Rule (2017)