The Effect of Caffeine on Positive Affect

Abstract

Prior research has shown that caffeine increases feelings of alertness and decreases sleepiness (Haskell et al., 2005, Attwood et al., 2007). However, the effect of caffeine on mood is unclear, with some studies finding that caffeine consumption increased positive mood and others associating caffeine with negative mood (Childs & De Wit, 2006, Attwood et al., 2007). The “msqR” dataset by the Personality, Motivation, and Cognition Laboratory at Northwestern University was downloaded from the RStudio package “psychTools”. This dataset contains response data from student participants who did or did not consume caffeine before taking the Motivational State Questionnaire-Revised Form (MSQ-R), which is a questionnaire of 72 mood items. A subset of these items have been shown to reflect positive affect (Watson et al., 1988). I carried out an independent samples t-test to compare the positive affect scores of those who consumed caffeine and those who did not, finding that caffeine consumption was significantly associated with decreased positive mood