Can you conceive of a scenario that would provide experience and observations that would refute your claim that “this is what determines how a person acts”?
Also, can you describe one example of your own experience or observation that has already provided you with what you believe is evidence in support of your claim that “this is what determines how a person acts”?
In the meantime, let’s consider an imaginary scenario. Two people are playing chess with (or perhaps we should say “against”) each other. You observe them in person, face-to-face. They are not actors playing a role. You do not know this, but one player is pursuing the goal of a draw, and is making an effort to refrain from checkmating his or her opponent. You cannot see what moves the players are considering but not making. Do you acknowledge that in this situation, nothing that you observe – not even a player’s authentic emotional reaction of surprise or sadness – can support your claim that “this is what determines how a person acts”?