Predictive Validity of Thin-Slice Nonverbal Behavior from Social Interactions.

We present five studies investigating the predictive validity of thin slices of nonverbal behavior (NVB). Predictive validity of thin slices refers to how well behavior slices excerpted from longer video predict other measured variables. Using six NVBs, we compared predictive validity of slices of different lengths with that obtained when coding is based on full-length (5-min) video, investigating the relative predictive validity of 1-min slices as well as of cumulative slices. Results indicate some loss in predictive validity with 1-min slices, but relatively little loss when Slices 1 and 2 were combined for five of the six NVBs. This research establishes an empirical basis on which researchers can decide how much of their recorded corpus needs to be coded for NVB. The results also provide some guidance on effect sizes in power analyses for researchers coding specific behaviors in a thin-slice design.