Simplicity Preference Is Adaptive

Human cognition systematically favors simpler explanations, concepts, and models (Chater & Vitanyi, 2003; Feldman, 2000; Lombrozo, 2007). This preference is typically treated as a heuristic: useful but without principled justification for why simpler hypotheses are more likely true. This paper provides the missing justification. Under the Simplicity Dominance Principle (SDP), where a structure's measure is P(S) proportional to 2^(-K(S)) with K denoting Kolmogorov complexity, simpler structures are exponentially more probable. Each additional bit of specification halves a structure's measure. This is a mathematical fact about the distribution of structures. If simpler explanations describe more probable structures, then organisms that preferentially adopt simpler explanations will, on average, act on more accurate models. Natural selection therefore favors simplicity preference. The preference is a calibration to the actual distribution of structures. This framework unifies several findings in cognitive science: why children learn regular patterns before exceptions, why concept difficulty tracks description length, why explanatory breadth is preferred over narrowness, and why conspiracy theories provoke cognitive resistance despite fitting the data. The paper also distinguishes the mathematical criterion (brevity of generating description) from the aesthetic response (perceived elegance or beauty), arguing that the latter is an evolved proxy for the former.