Nonverbal communication includes visual cues like body language, gestures, eye contact, facial expressions, as well as proxemics, chronemics, haptics and paralanguage. It represents around two-thirds of interpersonal communication and helps form first impressions. Research on nonverbal communication started with Darwin's 1872 work on emotional expressions across species. Key aspects of nonverbal communication examined include posture, clothing, gestures, eye contact and touch, which all have cultural variations in meaning and acceptability.