How does the text characterize the distinction between Norman’s contribution and subsequent practical rules like Nielsen’s?

Answer

Norman gave the why (design the whole experience), and subsequent leaders defined the how (specific, testable rules).

Norman provided the philosophical framework and justification for holistic design (the 'why'), while leaders who followed helped to define the specific, practical, and testable guidelines (the 'how') for achieving that experience.

How does the text characterize the distinction between Norman’s contribution and subsequent practical rules like Nielsen’s?
inventionprincipleuser experienceUX design