Final answer:
Biological psychology, or behavioral neuroscience, is the study of how the nervous system influences behavior and mental processes, and is an aspect of the wider field of neuroscience.
Step-by-step explanation:
The field of science that investigates the relationships between the nervous system and behavior/mental processes is biological psychology, which is also known as behavioral neuroscience. This interdisciplinary field encompasses neurobiology and investigates how our biology, specifically the nervous system, influences our behavior. Biological psychologists draw upon methods from psychology and physiology, among other areas, as they examine subjects such as sensory and motor systems, neurodevelopment, and the neural correlates of psychological disorders. It is a part of broader neuroscience research that also includes molecular, cellular, developmental, medical, and computational approaches to the study of the nervous system.