In his observations of heterosexual strangers in bar situations, Perper found if people were mutually attracted to each other the first indication was what?

Amswer:

They turn their bodies more toward each other until they are facing each other

Explanation: According to Perper, in his heterosexual Behaviors of persons in bar situation discovering that the when people starts getting equally attracted to each other, the first thing which they will possibly tend towards will be to bring their bodies towards facing each other.

Perper, did this research in a bar setting through which he reached the conclusion.