The Kuleshov Effect is a well-documented concept in film-making, discovered by Soviet film editor Lev Kuleshov in the 1920s. Kuleshov put a film together, showing the expression of an actor, edited together with a plate of soup, a dead woman, and a woman on a recliner. Audiences praised the subtle acting, showing an almost imperceptible expression of hunger, grief, or lust in turn. The reality, of course, is that the same clip of the actor’s face was re-used, and the effect is created entirely by its superimposition with other images.
– from TV Tropes
The essence of the Kuleshov effect is filling in the blanks, or connecting the dots. Mozhukhin isn’t actually looking at anything; he probably doesn’t even know what they’ll make him look at, so he can’t possibly be reacting to it. He expresses no emotion, so an audience cannot possibly see emotion on his face, but the audience does. The viewer is presented with a situation or environment along with the academic fact that someone is experiencing it. He cannot simply accept the actor’s evident emotion, as none is given, so he decides what the appropriate response would be and assigns it to the actor.
from – http://kubrickfilms.tripod.com/id21.htm
Here’s Alfred Hitchcock’s description of the Kuleshov effect: