Eye contact
How much, and in what way
Eye contact is one of the most intimate acts in conversation, and almost no two cultures read it the same way.
Looking someone in the eye while they talk can signal respect, engagement, and honesty in some settings. In others, sustained eye contact is a challenge, an intrusion, or a sign of aggression. The same glance that says 'I am listening' in one context can say 'I am confronting you' in another.
The nuances multiply when you factor in hierarchy, gender, and age. How much eye contact is appropriate from a younger person to an older one? From an employee to a boss? Across genders? These layers mean that a single norm about eye contact rarely covers all the situations within a single culture, let alone across many.