Behavioural sciences have a long-standing line of research providing evidence that people have numerous biases in their judgments and decisions. Probabilities for events are often communicated as percentages in whole numbers. Another option is a ratio that consists of a numerator and a denominator. This option is most common for very low probabilities that are difficult to understand and do not portray immediate relevance for people. Hence, likelihoods are communicated in ratios instead of percentages due to their greater impact. However, the comprehension of a ratio is not free from error. First of all, a person has to have a good understanding of the numbers that are representing the ratio. But even if there is no lack in numeracy, there is still a well-known systematic deviation from the expected outcome when ratios are applied which is called the ratio bias. In the four previous decades, overall five distinct prominent models have evolved to explain the ratio bias phenomenon. All these models are to some extent tied to dual process theories which are namely norm theory, cognitive-experiential self-theory, fuzzy-trace theory, anchoring and adjustment model, and component reasoning model. However, these models do not explain individual differences based on education. In overall five international studies (N = 849), we established that there is a highly significant difference in ratio bias among students in social sciences and students in STEM. Furthermore, our results suggested that statistical numeracy does not explain different choices. In contrast, we found that a preference for intuition or deliberation moderates the choices revealing the ratio bias. The higher the preference for intuition the more likely participants chose in line with the ratio bias. The higher the preference for deliberation the less likely participants chose the option reflecting the ratio bias. In addition, we found significantly different distributions of the preferences among our two study clusters. We discuss previous ratio bias models based on our results regarding preferences for intuition and deliberation and future advances in the research on the ratio bias.