
"Sometimes a cigar is just a cigar"
(but it's probably a penis)
Psychoanalytic Film Theory
Psychoanalytic film theory is a school of academic film criticism developed by Christian Metz, based on Freudian psychology and Jacques Lacan's mirror stage. It analyses how watching a film reconstructs the psyche of the spectator.
Paging Dr. Freud...
Dr. Sigmund Freud was an Austrian neurologist, often credited as the father of psychology. Freudian psychology posits that the human psyche is composed of the id, ego, and superego, and the interactions of these three constructs determined the behavior of the human.
The id comprises the basic, instinctual drives, such as hunger, lust and fear. It acts according to the "pleasure principle", meaning that every wishful impulse should be satisfied immediately, regardless of consequence. With the id alone, humankind is essentially no different from any animal. Freud described the id as having two instincts that are opposites, yet equally present: the life instinct and death instinct. The life instinct is the desire to create organic life via procreation while the death instinct mirrored the life instinct by being a desire to send organic life back into death.
The superego essentially acts as the person's critical and moralizing conscience, incoporating the values and morals as established by society. While the id desires simple self-gratification, the superego desires for the person's behavior to be based on what is socially acceptable. It criticizes the id's desires and controls the person's morality and sense of right and wrong.
The ego is construct that most closely resembles an actual human mind. It is the organized part of the consciousness and organizes the rest of the psyche into something coherent and productive. While the id acts based on the "pleasure principle", the ego acts on the "reality principle", or the need to reconcile the primal urges of the id with societal demands for appropriate behavior. Freud thought of the ego as the middleman between the id and the superego, taking the id's self-gratification and organizing it in a way that complies with both the superego's demands and the conditions of the real world, with the superego punishing the ego with feelings of guilt, anxiety, or inferiority if the ego acts out of line. The ego is therefore said to be driven by the id and confined by the superego.
Dr. Freud isn't in. Please refer to his student, Mr. Lacan.
Jacques Marie Émile Lacan was a French psychoanalyst and psychiatrist whose ideas had significant impact on multiple schools of thought, including but not limited to clinical psychoanalysis, film theory and sociology. Many, if not most of his works revolve around revisiting and rethinking Freudian psychology, particularly the concept of the ego. His first offical contribution to psychoanalysis was the mirror stage, or how the infant's "ego comes into being through the infant's identification with an image of its own body" (Flitterman-Lewis, 1987).
Put simply, between the ages of six and eighteen months, the infant has no ego and merely "perceives itself as a mass of disconnected, fragmentary movements" (Flitterman-Lewis, 1987). When the infant first sees its image in the form of a reflection or another person's face, it regards the image as unified, coherent and therefore superior self. It thus identifies with the image and internalizes it as the "ideal ego". By striving to achieve that "ideal ego", the infant thus forms its own ego. This inital formation of the ego is known as primary identification.
Wait, you're a film student? This is the psychology faculty, moron! Go look for Mr. Metz at film.
Christian Metz was a French film theorist who first applied psychoanalytic theories to film studies, creating the framework known as psychoanalytic film theory.
THE COMPLETE IDIOT'S GUIDE TO PSYCHOANALYTIC FILM THEORY
Step 1:
The viewer regresses to a state before his ego was formed.
“the totalizing, womblike effects of the film viewing situation represent, for him, the activation of an unconscious desire to return to an earlier state of psychic development, one before the formation of the ego” (Flitterman-Lewis, 1987)

The darkened theatre and the immobilization of the viewer recreates the conditions of the womb, encouraging the viewer's psyche to regress to its infant state, when the ego had not yet formed.
Step 2:
The viewer identifies with a transcendental, omniscient being.
“the spectator identifies with himself, with himself as a pure act of perception” (Metz, 1982)

Like the infant, the viewer has to undergo primary identification in order to reform his ego. However, unlike the infant, there is no reflected image for the viewer to identify with. As such, the viewer identifies with an all-seeing being as he is able to see all that is going on on-screen while the in-universe characters cannot.
Step 3:
After which, the viewer can identify with the characters on screen.
“[This identification] is what makes all secondary identifications with characters and events on the screen possible” (Flitterman-Lewis, 1987)

After undergoing primary identification, the viewer can engage in secondary identification, or identifying with the characters on screen. This not only mean identifying with a character's ego, it also means identifying certain characters as certain parts of the psyche, e.g. the villain as the id and the mentor figure as the superego.
Step 4:
The viewer's ego then continually reconstructs itself as it watches the film
"the film viewer both loses him/herself and refinds him/herself ... by continually reenacting the first fictive moment of identification and establishment of identity" (Flitterman-Lewis, 1987)

As the viewer watches the film, his ego is destroyed and rebuilt repeatedly, each time incoporating new aspects that are influenced by the film. For instance, the behaviors of the villain may lead to the viewer repressing the same behaviors exhibited by the id. As such, the ego of the viewer is reshaped by the values and characters shown in the film and it is continually reshaped until the film ends.

I ship you and your reflection