To the multi-disciplinary point above, I think Kahneman's economic work is largely categorized as behavioral economics. That's not divorced from group dynamics, as it tries to understand how social preferences, social utility, and other psychological factors shape strategic decision-making behavior.
There's also the fact that the economics profession, and the Economics Nobel committee, have both been making pains to include a broader set of dynamics under their scope. Among the more notably economic polymaths prior to Kahneman was Herbert A. Simon, possibly better known to the HN crowd for his pioneering work in AI and computer science, though he also worked in economics and, again, psychology. He was awarded the 1967 Nobel in economics on decision-making in the context of bounded rationality.
