Overlapping features during fear and surprise. The common element associated with fear and surprise is the raised eyebrows and wide-open eyes. Overlapping features during interest and surprise. The open mouth occurs during both interest and surprise. When seen alone in the center figure, the open mouth produces an ambiguous expression which may have no counterpart in real life.
Listeners looks far more than speakers.
People tend to look at that things that interests them most. It's unpolite to stare, especially to stare at strangers.