Does coffee make you reason smarter? The effect of caffeine on executive functioning and dual-process reasoning

Does coffee make you reason smarter? The effect of caffeine on executive functioning and dual-process reasoning. Katrijn Pipijn (Katrijn.Pipijn@ppw.kuleuven.be) Laboratory of Experimental Psychology, Tiensestraat 102 Bus 3711 3000 LEUVEN, Belgium Leen Janssens (Leen.Janssens@ppw.kuleuven.be) Laboratory of Experimental Psychology, Tiensestraat 102 Bus 3711 3000 LEUVEN, Belgium Stievy Visterin Laboratory of Experimental Psychology, Tiensestraat 102 Bus 3711 3000 LEUVEN, Belgium Walter Schaeken (Walter.Schaeken@ppw.kuleuven.be) Laboratory of Experimental Psychology, Tiensestraat 102 Bus 3711 3000 LEUVEN, Belgium Abstract In a setup based on the Masicampo and Baumeister (2008) lemonade study, the effects of caffeine on dual-process reasoning were explored. Participants in this double-blind study were divided into a caffeine and a caffeine-free control group. Participants had to solve several classical dual-process paradigms. Participants in the caffeine group were expected to perform better on analytic reasoning trials. In a follow-up experiment participants were also given an unexpected implicit recollection task to see whether caffeine has an affect on conflict monitoring, an executive function underlying dual-process reasoning. Even though the paradigms being used proved to be appropriate for dual-process testing, no effects of caffeine on dual-process reasoning or on conflict monitoring were found. Keywords: Dual-process reasoning, conflict monitoring, executive functions, caffeine Literature On average, people drink about 148 liters of coffee each year. Although reasons for drinking coffee vary between different people, an often recurring reason is a subjective feeling of better cognitive performance. For example, a student in the middle of an exam period or an employee with a high workload may think they will perform better after a couple cups of coffee. In our study, we found out whether or not dual-process reasoning is influenced by those cups and whether coffee is the elixir many people take it for. Research in thinking and reasoning repeatedly concluded that human reasoning is supported by two distinctive systems and can be considered dual-process reasoning. Two very easy-to-use and neutral terms for these two Systems were proposed by Stanovich (1999) and Stanovich and West (2000), System 1 and System 2. System 1, which can be described as an instinctive System, that is formed by associative learning processes, works rapidly, parallel, and automatically, and is based on heuristic reasoning. System 2 on the other hand is capable of abstract hypothetical thinking. It requires more mental resources and works much slower. System 1 is believed to do the primary reasoning whereas System 2 has the ability to override, inhibit or correct the default responses produced by System 1. System 2’s location in the brain has repeatedly been explored and one of its main locations is believed to be the prefrontal cortex (Goel, Buchel, Frith, & Dolan, 2000; Goel & Dolan, 2003; De Neys & Goel, 2011). Reasoning researchers increasingly believe that System 2 has a high inhibitory role and thus will be supported by the central executive System. For an extensive review on dual-process reasoning, see Evans (2008). In our current study, we looked at the effects of caffeine on these dual-process reasoning Systems. In 2008, Masicampo and Baumeister found that the ingestion of sugar enhanced the reliance on System 2 reasoning. They tested whether more blood glucose is needed for the highly demanding System 2 processes than is needed for System 1. They found that when participants had to complete highly demanding tasks, which relied on executive functioning, their blood glucose levels dropped. Not enough glucose remained available after these tasks for System 2 to operate optimally. As a result, System 2’s influence in subsequent tasks decreased. The low levels of glucose had a diminishing effect on dual-process reasoning tasks, which participants performed later on. When the blood glucose levels were restored by administering sugar- holding lemonade, System 2 regained functionality and performances on the dual-process tasks recovered to normal. The participants performed better in the dual-process reasoning tasks compared to the control group which was depleted but received sugar-free lemonade and the control group which was not depleted in the first place. Pocheptsova, Amir, Dhar, and Baumeister (2009) found that depleting participants of their limited resource of glucose by giving them self-regulating tasks, influences their