What is the author's style in Mourning Becomes Electra by Eugene O'Neill?

Naturalism is a nineteenth-century theory that developed in the wake of Darwin's theory of evolution. Naturalists perceived people as products of their heredity and environment. Naturalistic drama presents a vision of human life as akin to that of animal nature, in which these Darwinian drives motivate people. In many ways, these forces of nature minimize or even eliminate the individual's free will.

Naturalistic elements in Mourning Becomes Electro, include the ways the characters' personal histories and environments determine their actions and motivations.

Expressionism is a style of art that expresses internal experiences and psychological truth. Such art does not present a realistic image of world, but instead tries to create in the viewer a powerful "true" experience of a particular emotion, feeling, or state of mind.

Many of O'Neill's plays have expressionistic elements: masks, which conceal the actor's faces; and asides, in which actors address the audience without others on stage hearing. Expressionistic elements in Mourning Becomes Electra include the pairing of characters (Lavinia resembles Christine and Orin resembles Ezra) and the symbolism of the Mannon house, which resembles a Greek temple.