It was around the beginning of 1917 when Stanislavski began to examine purposeful action (i.e. psychophysical action) with greater depth. In essence, psychophysical actions are physical actions that inspire feelings. Instead of interpreting action as a result of emotions, Stanislavski believed that emotions were the result of purposeful action.
For instance, a character sits at the dining table. He gets up and flings the plate at the wall, causing him to feel angrier and more frustrated. A character slouches on the chair, making him feel lethargic and lazy. A character gives another character a hug. Now they feel closer and happier as a result of the hug.
As you can tell, psychophysical action hinges on the relationship between mind and body. The actor has to then recognize and be sensitive to the emotional sensations engendered by physical action, accept these feelings and respond to them. Imagination comes into play when the actor’s emotions are triggered. In order to remain rooted to the happenings of the world on stage, the actor must use his imagination to funnel his emotions into the scene.
So how exactly is this useful? Well psychophysical action seeks to bridge the gap between what we understand from the text and what we are actually feeling. However, since emotions can be elusive, Stanislavski’s Psychophysical Action is a way for actors to ground and conjure emotional states more readily, through bodily expression such as breathing patterns or tension.