Double Dissociation

Double dissociation is strong evidence that two cognitive functions are actually separate, not one thing in disguise.

The pattern:

• lesion X impairs A, not B
• lesion Y impairs B, not A

Broca vs Wernicke

Broca’s Area damage impairs speech production but leaves comprehension relatively intact; Wernicke’s Area damage does the opposite. Production and comprehension are separable abilities.

The question it asks: are these two abilities actually different things?