The central executive is theorized to be an overarching cognitive system responsible for coordinatingprocesses that enable self-control (i.e., inhibiting habitual responses), persistence at mental andphysical tasks, emotional regulation and working memory (Gailliot, 2008; Miller & Cohen, 2001).There is evidence that the executive system relies on glucose as its energy resource (Gailliot et al.,2007) and that when humans invoke the central executive they expend large quantities of glucose.When glucose levels are low, humans perform more poorly on other tasks that rely on the central executive (Gailliot et al., 2007). Similar results have been obtained with non-human animals. When dogs are required to exert self-control on an initial task they persist for a shorter duration at asubsequent unrewarding task and are more impulsive than if they were not required to exert selfcontrol(Miller, DeWall, Pattison, Molet, & Zentall, in press; Miller, Pattison, Rayburn-Reeves,DeWall, & Zentall, 2010). Given the similarities between human and non-human animals, further research on executive control processing and glucose depletion with non-human animals is encouraged. Such research may lead to interventions that sustain and replenish executive control.

Prior research, using two- and three-dimensional environments, has found that when both human and nonhuman animals independently acquire two associations between landmarks with a common landmark (e.g., LM1-LM2 and LM2-LM3), each with its own spatial relationship, they behave as if the two unique LMs have a known spatial relationship despite their never having been paired. Seemingly, they have integrated the two associations to create a third association with its own spatial relationship (LM1-LM3). Using sensory preconditioning (Experiment 1) and second-order conditioning (Experiment 2) procedures, we found that human participants integrated information about the boundaries of pathways to locate a goal within a three-dimensional virtual environment in the absence of any relevant landmarks. Spatial integration depended on the participant experiencing a common boundary feature with which to link the pathways. These results suggest that the principles of associative learning also apply to the boundaries of an environment.