The term feedback originates in cibernetics (Wiener, 1948), where it is used to denote processes by which a control unit gets information about the effects and consequences of its actions. Linguistic Feedback (Allwood 1979, 1988) is the linguistic mechanism which enable the participants of a conversation to exchange information about the four basic communicative functions which are essential in human direct face-to-face cmmunication. These function are: contact (willing/able to continue), perception (willing/able to perceive), understanding (willing/able to understand), and attitudinal reactions (willing/able to react).

Allwood, J., Nivre, J., and Ahlsén, E. (1993). On the semantics and pragmatics of linguistic feedback. Journal of Semantics, 9(1):1–29. Available from: http://wwwantique.ling.gu.se/jens/publications/B%2520files/B33.pdf.