Retrieving information from a hierarchical plan.

Plans give structure to behavior by specifying whether and when different tasks must be performed. However, the structure of behavior need not mirror the structure of the plan. To investigate this idea, the authors studied how plan information is retrieved in the context of a novel sequence-position cuing procedure, wherein subjects memorize two task sequences, then perform trials on which they are randomly cued to perform a task at one of the serial positions in a sequence. Several empirical effects were consistent with retrieval from a hierarchically structured representation (but not a non-hierarchical representation), including large sequence-repetition benefits, position-repetition benefits only for sequence repetitions, and a lack of robust task-repetition benefits. The data were successfully modeled by assuming that retrieval was time-consuming, susceptible to priming, cue-dependent, structurally constrained, and token-specific. In tandem, the empirical data and modeling work provide deeper insight into the representation of and access to information in memory that comprises a plan for guiding behavior.