Question

The branch of psychology that emphasizes that perception is more than the sum of its parts is

Answer 1

"gestalt psychology."

Gestalt psychology tells us that our minds can naturally fill in missing pieces, all on their own.

Take a look a the picture that I drew.

Answer 2

The shape is incomplete.
See that little missing space there?
This drawing is not finished.

But we already know that it's a triangle,
even though it has a missing piece.

Why?

Because our minds can fill in the missing piece.

That's an example of gestalt psychology.