Researchers in Scotland say a belief there are six basic emotions universally recognized through specific facial expressions is wrong -- there are just four. A belief has been commonly held that happiness, sadness, fear, anger, surprise and disgust are easily interpreted through facial expressions, regardless of language or culture. Scientists at the University of Glasgow suggest that fear and surprise initially share a common signal -- wide open eyes -- and anger and disgust share another common initial facial expression, a wrinkled nose. While the facial expression signals of happiness and sadness are clearly distinct across time across cultures, the fear/surprise and anger/disgust pairing share similar facial expression characteristics not always easy to separate, they said. Fear/surprise and anger/disgust can be confused at the early stage of expression and only became clearer later when other facial elements come into play, they said. "We show that 'basic' facial expression signals are perceptually segmented across time and follow an evolving hierarchy of signals over time -- from the biologically-rooted basic signals to more complex socially-specific signals," lead researcher Rachael Jack said. "Our research questions the notion that human emotion communication comprises six basic, psychologically irreducible categories," she said. "Instead we suggest there are four basic expressions of emotion."