Task dependent conflict has been shown to reduce metacognitive judgements of confidence and prolong response times in various reasoning tasks. For this study a modified version of the base rate task was used to induce conflict while measuring response times and judgements of confidence. The aim of this experiment was to determine the influence of different instruction conditions (reasoning according to belief or according to mathematical probability) on fluency and metacognitive judgements. As expected, participants experienced higher levels of conflict when reasoning according to mathematical probability even though conflict effects were present in both conditions. Additionally, higher believability items mitigated conflict influence while reasoning in accordance with belief and increased it when reasoning in accordance with mathematical probability. These results enrich the growing field of metareasoning research and are discussed as such.