He is an expert in experimental psychology.

He is known as an expert in criminology.

She is majoring in clinical psychology.

He has a deep interest in parapsychology.

He is known as a person with learning.

If you keep looking at the same character for a long time, you may experience the Gestaltzerfall phenomenon.

He studied Gestalt therapy and deepened his self-understanding.

He is a specialist in that field.

He has expert knowledge.

He is studying computer science at a specialized school.