We see this phenomenon at work (or a related one) all the time in the form of social referencing. Of which the classic would be the toddler who falls, checks to see if caretaker is signaling distress, and then chooses to cry based on the response. It's also fairly well established that first responders and mental health professionals can (and often do) develop secondary trauma responses (secondary PTSD) without having witnessed the trauma at all, just from working with the distress of those with primary trauma.
