Naturalism is like realism on steroids, or at least like realism with a slant. Naturalism might be considered a form of realism, or a progression of realism.
Realism is something of a synonym with verisimilitude. Realism attempts to portray reality. It attempts to give the impression of depicting actuality.
Naturalism does the same, but it usually centers on people who are victims of natural or societal forces. Thus, it usually tries to realistically portray human victims of nature or society. There can also be a scientific component to naturalism. Naturalism sees humans as animals like any other creatures. Science explains humans and their frailties, and science is dominant over religious concerns.
In Synge's The Shadow of the Glen, Nora Burke is such a victim. She marries for the sake of security, but finds only misery in her marriage. She is trapped by forces beyond her control: the human need for security and society's dictates concerning marriage.
Nora actually breaks free, however, which is not always the case in naturalistic fiction: she leaves with the tramp.
realism is more about the relations between people sociologically, plays such as isbens centre on this
When looking at naturalism the character will be effected directly by their environment. Refer to Woyzeck by Buchner.
Naturalism devotes to darwinisms theories and is more obsessed with the philosophy that our environment shapes us, look for lengthy scientific prose or scientific ramblings.
Realism will show up more when characters are more centred on themselves as a person and their direct actions, taking responsibility for themselves, relating to one another quite logically.
I dont know the play you are asking about but pay particular notice to the ways in which different characters speakto one another.
not an authority onthe subject but am myself inthe middle of an essay making a distinction between realism andnaturalism in plays by Buchner, Isben and Wedekind. (Woyzeck, Buchner;A Doll's House, Isben; Springs Awakening, Wedekind)
The two can often show up in oe play so focus on logic for realism and environmental and heriditory influence over actions for Naturalism.
Realism= the person, and the aaction;
Naturlism= Character manipulated by environmental, hereditory factors, not completely responsible for their actions.
Realism as with Naturalism focus on sociology strongly. specifically the social structureof the burgoise.