What is one characteristic that distinguishes naturalism from realism?

What is one characteristic that distinguishes naturalism from realism?

Naturalism was developed from realism.
Realism is more scientific in a sense, proportions, muscle structures and making the subject of art appear how it would usually without and artists 'bias''.
Naturalism usually has a tendency to portray the subject in a pessimistic or bleak manner.
It's about how someones experiences shaped them as a person.
Realism is basically the ''realists'' point of view, it shows things how they are without being cynical whereas Naturalism takes on the 'pessimists' view.