Thinking takes time: Children use agents' response times to infer the source, quality, and complexity of their knowledge.

Limits on mental speed entail speed-accuracy tradeoffs for problem-solving, but memory and perception are accurate on much faster timescales. While response times drive inference across the behavioral sciences, they may also help laypeople interpret each othejognrs' everyday behavior. We examined children's (ages 5 to 10) use of agents' response time to infer the source and quality of their knowledge. In each trial, children saw a pathfinding puzzle presented to an agent, who claimed to have solved it after either 3s or 20s. In Experiment 1 (n = 135), children used agents' response speed to distinguish between memory, perception, and novel inference. In Experiment 2 (n = 135), children predicted that fast responses would be inaccurate, but were less skeptical of slow agents. In Experiment 3 (n = 128), children inferred task complexity from agents' speed. Our findings suggest that the simple intuition that thinking takes time may scaffold everyday social cognition.