Aseries of dots arranged in the shape of a face will be perceived as a face, not a series of dots. a psychologist studying this phenomenon is applying the principals of gestalt psychology

I believe the answer is: Gestalt psychology

Gestalt psychologist is operating on the assumption that sensory experiences could be differentiates into smaller parts. Which is why even when people is made to face something that seem chaotic or disorderly, we can still formulate something that is common/generally accepted.

answer; the parasympathetic nervous system;