title: Feeling smart: Effects of caffeine and glucose on cognition, mood and self-judgment.
abstract: During education and early career, young adults often face examinations and assessment centers. Coffee and energy drinks are convenient and commonly used to enhance or maintain performance in these situations. Whether these macronutrients improve performance in a demanding and drawn-out multi-task situation is not clear. Using double-blind, placebo-controlled studies, we set out to examine the effects of caffeine and glucose in an assessment center-like situation, under natural consumption conditions, in a group of young adults who were heterogeneous with respect to consumption patterns. We measured multi-task performance including logical thinking, processing speed, numeric and verbal memory, attention and the ability to concentrate, and mood over a two-hour period. Caffeine and glucose were administered in common beverages with appropriate placebo controls allowing the assessment of psychological effects of expectancy. Importantly, and in contrast to most previous studies, participants retained their habitual caffeine and sugar intake (studies 1 and 2) as this represents common behavior. Based on the bulk of literature, we hypothesized that (i) caffeine enhances attentional performance and mood, while performance in more complex tasks will remain unchanged, and that (ii) glucose enhances performance on memory tasks accompanied with negative mood. Our results provide evidence that neither caffeine nor glucose significantly influence cognitive performance when compared with placebo, water, or no treatment controls in a multi-task setting. Yet, caffeine and, by trend, placebo improve dispositions such that participants perceive preserved mental energy throughout the test procedure. These subjective effects were stronger after 24 h caffeine abstinence (study 3). Future studies will have to address whether these mood changes actually result in increased motivation during a challenging task.
authors: Psychophysiology of Food Perception, German Institute of Human Nutrition Potsdam-Rehbrücke, Arthur-Scheunert-Allee 114-116, 14558 Nuthetal, Germany. Electronic address: susann_ullrich@msn.com.
authors: Susann
authors: S
authors: Ullrich
authors: Psychophysiology of Food Perception, German Institute of Human Nutrition Potsdam-Rehbrücke, Arthur-Scheunert-Allee 114-116, 14558 Nuthetal, Germany.
authors: Yfke C
authors: YC
authors: de Vries
authors: Center for Lifespan Psychology, Max Planck Institute for Human Development, Lentzeallee 94, 14195 Berlin, Germany; Clinic and Policlinic for Psychiatry and Psychotherapy University Clinic Hamburg-Eppendorf, Martinistraße 52, 20246 Hamburg, Germany. Electronic address: kuehn@mpib-berlin.mpg.de.
authors: Simone
authors: S
authors: Kühn
authors: Department of Psychiatry and Psychotherapy, Charité Universitätsmedizin, Campus Benjamin Franklin, Hindenburgdamm 30, 12203 Berlin, Germany. Electronic address: dimitris.repantis@charite.de.
authors: Dimitris
authors: D
authors: Repantis
authors: Donders Institute for Brain, Cognition and Behaviour, Radboud University Medical Centre, P.O. Box 9010, 6500 GL Nijmegen, The Netherlands; Max Planck Institute of Psychiatry, Kraepelinstraße 2-10, 80804 Munich, Germany. Electronic address: martin.dresler@donders.ru.nl.
authors: Martin
authors: M
authors: Dresler
authors: Psychophysiology of Food Perception, German Institute of Human Nutrition Potsdam-Rehbrücke, Arthur-Scheunert-Allee 114-116, 14558 Nuthetal, Germany. Electronic address: ohla@dife.de.
authors: Kathrin
authors: K
authors: Ohla
mesh_terms: D000328:Adult; D000339:Affect / Q000187:drug effects* / Q000502:physiology; D002110:Caffeine / Q000008:administration & dosage*; D004311:Double-Blind Method; D060766:Drinking Water / Q000008:administration & dosage; D005247:Feeding Behavior; D005947:Glucose / Q000008:administration & dosage*; D006801:Humans; D008297:Male; D005222:Mental Fatigue / Q000188:drug therapy / Q000378:metabolism; D008606:Mental Processes / Q000187:drug effects* / Q000502:physiology; D011581:Psychological Tests; D012649:Self Concept; D012907:Smoking; D055815:Young Adult
chemical_list: D060766:Drinking Water; D002110:Caffeine; D005947:Glucose
keywords: Caffeine; Cognition; Glucose; Mood; Performance