The Psychological Record, 2013, 63, 1–12 Correspondence concerning this paper should be addressed to Stephen Ray Flora, Department of Psychology, Youngstown State University, Youngstown, OH 44555; E-mail: srflora@ysu.edu DOI: EFFECTS OF SUGAR CONSUMPTION ON HUMAN BEHAVIOR AND PERFORMANCE Stephen Ray Flora and Courtney Allyn Polenick Youngstown State University It is a myth, disconfirmed by numerous studies, that sugar consumption causes hyperactivity or other behavior problems in children or adults. This myth may be maintained by confirmation bias and social reinforcement. Conversely, numerous studies show that sugar consumption improves athletic, cognitive, and academic performance and may increase self-control and reduce aggressive behavior. These effects may be most apparent shortly after sugar has been consumed. While the brain utilizes large amounts of glucose, the exact physiological mechanisms responsible for the performance-enhancing effects of sugar consumption are still debated. Psychological research and theorizing on the effects of sugar consumption should avoid speculative explanations in terms of “mind” and “willpower,” and focus on observed behavioral effects. For behavior and academic problems, limiting sugar consumption should not be a treatment focus and may be counterproductive. Key words : sugar, self-control, hyperactivity, willpower, confirmation bias Avoiding tooth decay, diabetes, and obesity are all good reasons to limit consumption of sugar in the human diet. But sugar consumption, even in high amounts, does not contribute to hyperactivity, inattention, juvenile delinquency, reductions in cognitive performance, or other behavior problems in children or adults. Instead, a high level of glucose, or sugar, consumption actually improves athletic, academic, and cognitive performance, and may enhance self-control. Unless medically prescribed for non- behavioral reasons, dietary restriction of sugar intake is inappropriate and may have unintended behavioral effects (e.g., Fisher & Birch, 1999), create unnecessary interpersonal conflict, and be counterproductive by precluding consideration and implementation of proven effective interventions for behavioral and performance problems, such as behavior therapy as treatment for attention-deficit/hyperactivity disorder (ADHD; e.g., Fabiano et al., 2009). The Sugar–Hyperactivity Myth The myth that sugar consumption causes behavior problems may be maintained by confirmation bias and social reinforcement. Confirmation bias, the tendency to look for, and find, cases that confirm preexisting opinions and biases while ignoring disconfirming evidence, has been shown to aversively affect decision making in a vast range of human