Final answer:
A psychologist labeled as an interventionist believes in the importance of modifying the environment to change behavior. This aligns with the behaviorist perspective, which emphasizes external factors and learned behaviors over genetic or internal determinants.
Step-by-step explanation:
When a psychologist is labeled an interventionist, this means that they believe c) Intervening in the environment is essential to modifying behavior. An interventionist perspective is based on the idea that behavior can be changed through environmental manipulation rather than being wholly determined by genetics or biology. This view aligns with the behavioral perspective, where behaviorists, such as B.F. Skinner, posited that behavior is shaped by external reinforcements and consequences, rather than internal or inborn factors.
The field of behaviorism emphasizes that humans behave in a consistent manner based on prior learning, where the environment plays a crucial role in forming and altering behaviors. In contrast to more biologically oriented branches of psychology, such as evolutionary psychology or biopsychology, which focus on genetic and physiological bases of behavior, behaviorists and interventionists concentrate on how environmental factors, such as the social and physical environment, influence and can be altered to change behavior.
Thus, option c, which states that intervening in the environment is paramount to modifying behavior, aligns with the interventionist belief in the power of environmental influences over genetic determinism or internal factors, making it the correct answer to the question.