How did literary naturalism differ from realism?

Literary naturalism, a movement exemplified by American author Theodore Dreiser, extended the tradition of realism by aiming for an even more faithful and unselective representation of reality.12

While realism focused on detachment, objective observation, and a restrained critique of social mores, naturalism differed through its adoption of scientific determinism. Naturalistic authors viewed characters as helpless products of heredity and environment, driven by instinctual forces rather than rational or moral qualities.12

Key distinctions include:

• Determinism vs. Agency: Realism often maintained a sense of moral judgment or understanding regarding characters' choices, whereas naturalism presented characters as having little free will, often leading to pessimistic outcomes.12
• Scientific Approach: Naturalists acted as "detached experimenters," treating characters like specimens under a microscope to test how they reacted to social and economic pressures.1
• Subject Matter: While realism focused on ordinary people and contemporary life, naturalism frequently gravitated toward the most oppressive environments, such as slums or the underworld, documenting these milieus in sordid detail.12