Categorization decisions can be a matter of life or death. For example, animals must learn the categories of plants that are dangerous in order to avoid being poisoned. Humans can learn categories using at least two different brain systems; a rule-based system and a procedural system. The rule-based system categorizes objects according to simple verbalizable rules and relies on working memory, executive attention, and logical reasoning. Alternatively, the procedural system categorizes objects according to patterns that are difficult to describe verbally and are learned through a process of trial and error with fast and reliable feedback. When using the rule-based system participants are able to articulate their strategy because the conscious mind has access to this information; however, when participants use the procedural system they tend to tell the experimenter that they went with their gut.