Naive ecology is defined as the layperson's understanding of how organisms interact in and with the natural world, and all cognition, particularly causal cognition, in which that understanding is evoked. Stimulus materials in this study described a simple model of a food web. Participants judged how to bring about a particular stable change in the food web, and also the effects of different kinds of disturbance within the food web. Their judgments showed a consistent tendency named the dissipation effect: a tendency to judge that effects of a perturbation at a particular locus in an ecosystem weaken or dissipate as they spread out from that locus. The effect is not typical of real food webs. The finding may represent an effect of domain-specific acquired beliefs, or participants may have been making analogies with the properties of more familiar complex physical systems.