A physical interaction is one in which the participants know by way of input and feedback that the interaction is taking place.
A good physical interaction plays upon the strengths of the participants.
Televisions are good examples of what Crawford would call participatory, but not interactive digital technologies. The television generally receives infrequent input from the participant, the viewer, and will only play what is selected by the viewer. The viewer in turn may talk to the television, much like the movie example Crawford gives, but the TV doesn’t alter its performance based on the suggestions offered by the viewer. It also occurs to me that in calling one of the participants the viewer one may know all they need to know about whether or not a television is interactive or not.