Answer:
Epiphenomenon
Step-by-step explanation:
Epiphenomenon dictate the relationship between mind and body. When our mind is operating in a certain way, sometimes our body will create some sort of response that reveal that operation. This response tend to be involuntary and occurs on individuals without being learned.
Other perfect example would be people's tendency to rub/scratch their nose when they're lying. Granted that not all people do this, but a large portion of population from different cultures involuntary do this when they're telling lies or half truths. Currently, we still haven't figure it out the exact cause of this behavior. But, this often used as a sign during body language education.