Two experiments tested whether spreading activation or cue assimilation underlie incubation effects in problem solving. After initial attempts to solve remote associates tasks, participants performed lexical decision tasks that included solution words, and attempted the remote associates again, either immediately, after a delay with no interpolated task, or after a delay with filler tasks. Spreading activation of target lexical items was not influenced by incubation. However, the presence of solution words in interpolated lexical decision items gave rise to incubation effects with high cognitive-load incubation tasks. The results support a cue-assimilation process, in which unconscious processes access solution relevant information during incubation, but only if conscious task activity is suppressed. It is suggested that different mechanisms may occur during an incubation period to facilitate solution finding, depending on the nature of the impasse encountered during initial attempts.