Although it makes up only 2% of body weight, the brain uses about 75% of the glucose in the blood, making it by far the organ the most metabolically costly in the world. human body (Dunbar, 1998; Kahn, 2005). Glucose (the main type of sugar found in the blood) is the main source of energy for the brain and the rest of the body. When glucose levels are high, excess glucose is converted and stored as glycogen, which can then be metabolically converted back to glucose and used for energy. The energy cost is particularly high for mental tasks that recruit the "central executive" or areas of the brain that regulate cognitive and emotional control. These tasks reduce blood sugar at higher rates than other mental tasks that do not recruit the executive (Galliot & Baumeister, 2007). Additionally, many tasks that appear to require self-regulation and executive functions suffer when glucose is depleted and may show improved performance if glucose levels are restored. These tasks include avoiding prejudiced or stereotype-based behaviors (Galliot et al., 2009), being prepared to help strangers (DeWall, Baumeister, Galliot and Maner, 2008), monitoring performance in a situation of dual task (Scholey, Sunram-Lea, Greer, Elliot, & Kennedy, 2009), memory (Meikle, Riby, & Stollery, 2004), complex decision making (Masicampo & Baumeister, 2008); and persistence in difficult tasks (see Galliot, 2008 for a review). Most prior studies have used social cognition procedures that intuitively appear to require executive processing, but lack a direct, controlled comparison between demanding executive and non-executive conditions. Therefore, it is unclear whether glucose has its primary effects on the regulation of ex... middle of paper and the value of word imagery on human memory. Behavioral Neuroscience, 113, 431-438. Scholey, AB, Sunram-Lea, SI, Greer, J., Elliot, J., & Kennedy, DO (2009). Glucose administration before a divided attention task improves tracking performance but not word recognition: evidence against differential memory improvement? Psychopharmacology, 202, 549-558. Scholey, AB, Sunram-Lea, SI, Greer, J., Elliot, J., & Kennedy, DO (2009). Improving glucose memory depends on initial thirst. Appetite, 53, 426-429. Scholey, A.B., Harper, S., Kennedy, D.O. (2001). Cognitive demand and blood sugar levels. Physiology & Behavior, 73, 585-592. Sunram-Lea, S.I., Foster, J.K., Durlach, P., & Perez, C. (2002). The effect of retrograde and anterograde glucose administration on memory performance in healthy young adults. Behavioral brain research, 134, 505-516.