Why are the social sciences hard? Two new hypotheses.

Debates about whether the social sciences are harder than the natural sciences rarely analyze what discipline-level hardness amounts to. We offer a simple formal framework that models disciplines as sets of prediction tasks with associated difficulty, and links judgments of hardness to a discipline's best-achieved performance on such tasks and to the psychological impressiveness of those successes. Within this framework we develop two hypotheses about why the social sciences appear hard. The rigid demands hypothesis holds that, in the social sciences, we are precommitted to a narrow class of prediction tasks, which restricts the usual strategy of changing the question to a more tractable one and thereby lowers expected best performance. The fruit in the hand hypothesis holds that, due to evolutionary and cultural pressures, humans already solve many low-difficulty prediction tasks about human behavior, so these do not register as scientific successes and harder residual tasks dominate our impressions. We show that, even if task-level difficulty distributions were identical across domains, these mechanisms would make the social sciences appear harder than the natural sciences. This undermines straightforward inferences from differences in headline successes to claims about the intrinsic difficulty of the social domain. This framework opens new lines of inquiry regarding perceptions of the difficulty of the sciences.