Researchers have begun to evaluate whether nonhuman animals share humans' capacity for metacognitive monitoring and self-regulation. Using perception, memory, numerical, and foraging paradigms, they have tested apes, capuchins, a dolphin, macaques, pigeons, and rats. However, recent theoretical and formal-modeling work has confirmed that some paradigms allow the criticism that low-level associative mechanisms could create the appearance of uncertainty monitoring in animals. This possibility has become a central issue as researchers reflect on existing phenomena and pause to evaluate the area's current status. The present authors discuss the associative question and offer our evaluation of the field. Associative mechanisms explain poorly some of the area's important results. The next phase of research in this area should consolidate the gains achieved by those results and work toward a theoretical understanding of the cognitive and decisional (not associative) capacities that animals show in some of the referent experiments.Humans feel uncertain. They know when they do not know or remember, and they respond well to uncertainty by deferring response and seeking help or information. Their responses to doubt and uncertainty ground research on metacognition, or thinking about thinking (Benjamin et al.