Similar to Copeland, Gunawan, and Bies-Hernandez (2011), the present study investigated the influence of source expertise characteristics on people’s susceptibility to bias in syllogistic reasoning. Each syllogistic conclusion was presented by one of two sources: an expert or a non-expert. In the present experiment, the medium of presenting the source information was also altered to include visual images of the sources. Furthermore, individual differences measures were included in order to investigate whether working memory capacity and certain thinking styles (i.e., reflective or actively
open-minded thinking) are related to the source expertise bias. In contrast to the source expertise bias that Copeland et al. (2011) had found among their full sample of participants, only a specific sub-sample of the participants in the present experiment exhibited the bias. Namely, people who scored low on the Cognitive Reflection Test (Frederick, 2005) showed the source expertise bias, whereas those with high scores did not.