instinctivist

noun

in·​stinc·​tiv·​ist -tiv-əst 

: a person who views human behavior and social adaptation as the resultant of the interplay of various instinctive drives (as for survival) with environmental factors (as group relations)

instinctivist adjective

or instinctivistic

in-ˌstiŋ(k)-tiv-ˈist-ik