That we shape our environment, and our environment shapes us, are truisms with deep and complicated consequences. The resulting feedback interaction leads to a substantial form of what is known as path dependency. This is that small initial variations, stemming from individual differences or even just the vicissitudes of chance, can potentially result in large and persistent divergence in outcomes. This has implications for the nature and interpretation of adaptive and maladaptive choice. This chapter offers a simple formulation in terms of active observers—a formalization of decision-making problems in which actors have the choice of whether and how to gather information to improve what happens. The chapter notes that, according to Bayesian decision theory, it is often optimal for active observers to remain incorrectly calibrated with their surroundings; it explores consequences of this in non-interactive environments, and environments containing other people who might compete or cooperate. The chapter draws loose parallels with the literature on active and evocative gene–environment correlations.