Abstract
We examine cooperation in repeated interactions where intended actions are implemented with noise but intentions are perfectly observable. Observable intentions lead to more cooperation compared to control games where intentions are unobserved, allowing subjects to reach similar cooperation levels as in games without noise. Most subjects condition exclusively on intentions, and use simpler, lower-memory strategies compared to games where intentions are unobservable. When the returns to cooperation are high, some subjects are tolerant, using good outcomes to forgive attempted defections; when the returns to cooperation are low, some subjects are punitive, using bad outcomes to punish accidental defections.