Confirmation bias is commonly defined as the fact that “information is searched, interpreted, and remembered in such a way that it systematically impedes the possibility that the hypothesis will be rejected” (Oswald & Grosjean, 2004, p. 79). This bias is widespread and takes different forms (Nickerson, 1998; Klayman, 1995), and recent research has highlighted in particular its potentially large societal impact. When applied to political beliefs for instance, confirmation bias may contribute to the persistence of misinformation and conspiracy beliefs (e.g., Hattersley et al., 2022; Zhou & Shen, 2022) and political polarization (e.g., Lord et al., 1979; see Jost et al., 2022 for a recent review). Yet, and although confirmation bias has been described as “the best known and most widely accepted notion of inferential error to come out of the literature on human reasoning” (Evans, 1989, p. 41), it is still unclear how different manifestations of confirmation bias are related to each other.
Furthermore, one should distinguish between two aspects of confirmation bias commonly studied in the literature, which differ regarding the source of the hypotheses to test (internal vs. external), and their relevance to the participant’s values, beliefs and self-concept. On the one hand, confirmation bias can refer to the tendency to support one’s own prior views on a particular topic (e.g., death penalty, in Lord et al., 1979). In this case, it is sometimes referred to as a myside bias (Baron, 1995; Mercier 2017; Stanovich, 2021). On the other hand, confirmation bias was initially invoked to account for the participants’ tendency to confirm abstract/logical hypotheses that are not specifically related to their beliefs or values (Baron, 2008; Poletiek, 2001). This was the case, for instance, in the pioneering work of Wason (1960, 1966), described below.
The present study will only focus on this latter aspect of confirmation bias, with external hypotheses, rather than on myside bias. We have already noted that despite the apparent simplicity of the phenomenon, Oswald & Grosjean’s definition implies that confirmation bias is an umbrella term that encompasses at least three related though distinct stages (seeking, interpreting, and remembering) of information processing (Nickerson, 1998; Klayman, 1995; Oswald & Grosjean, 2004). Our goal is to better understand whether these different manifestations are distinct phenomena or whether they can be considered as three facets of a single phenomenon.
The concept of confirmation bias in hypothesis testing was introduced by Wason (1960) who designed a rule discovery task known as the 2-4-6 task. Participants were provided with three numbers (e.g., “2-4-6”) as an instance of a numerical rule, which they had to discover. For that purpose, they were instructed to put forward triples and the experimenter would tell them whether or not each triple complied with the rule. It turned out that participants usually tested triples that were compatible with the hypothesis they had in mind (e.g., the triple “10-12-14” to test the hypothesis that the rule at hand is “add 2”), suggesting that they aimed to confirm their hypothesis rather than to falsify it. The four-card problem (or selection) introduced by Wason (1966) is also typically used to demonstrate the tendency of participants to search for confirmatory information when testing logical (if-then) rules (Wason & Johnson-Laird, 1972). A similar finding was found using a trait hypothesis testing task in which participants are put in the position of interviewers and select questions to ask an interviewee to test a hypothesis about her personality (Snyder & Swann, 1978; Snyder & White, 1981). For instance, to test the hypothesis that the interviewee is extroverted, participants selected significantly more questions assuming that it was true (e.g., “What kind of situations do you seek out if you want to meet new people?”) than questions assuming that the alternative, introversion hypothesis, was true.
There has been considerable debate in the literature about whether the pattern observed in these tasks demonstrates a true confirmation strategy in hypothesis testing (Evans, 1989, 2014; Mercier, 2017; Oswald & Grosjean, 2004). For instance, behavior in the Wason task might reflect a matching bias by which participants tend to choose whichever cards happen to be named in the rule (Evans, 1972). A positive test strategy (Klayman & Ha, 1987; Klayman, 1995) or a congruence bias (Baron et al., 1988) have been also suggested, by which participants would ask only questions for which they expect a positive answer. As noted by Evans (2014), in the case of the classic 2-4-6 task, this positive test strategy fully overlaps with a confirmation strategy, as it would lead participants to only suggest sequences that would be confirmed by the experimenter. A diagnostic strategy, by which participants would ask questions that most clearly distinguish between the given hypothesis and its alternative(s) has also been discussed (Trope & Bassok, 1982, 1983; Devine et al., 1990).
While confirmation bias has been mainly studied with regard to information search using the different paradigms described above, it may also occur in the processes of weighing evidence and memory recall (Oswald & Grosjean, 2004). Several studies have evidenced that participants evaluated information incongruent with their attitude much more critically than congruent information (Lord et al., 1979), and retained their hypothesis when faced with ambiguous evidence (Hoch & Ha, 1986) or even clearly falsifying evidence (Beattie & Baron, 1988). With regard to memory recall, participants have a bias towards reporting information as previously encountered for confirming more than disconfirming information, whereas sensitivity measures of memory show no clear effect (Eagly et al., 1999; Stangor & Mcmillan, 1992).
So far, most studies focused on only one component of information processing and only one task/paradigm. One notable exception is the study by Vedejová and Čavojová (2022) who designed a unified procedure in which the three components of confirmation bias (i.e., information search, weighing of evidence, and memory recall) were evaluated within the same paradigm. However, this study has focused only on myside bias, and reported average effects for each component, without assessing score reliability and individual differences. Thus, how the different components of confirmation bias in hypothesis testing may relate to each other remains unclear. Within the variety of tasks associated with the phenomenon of confirmation bias, here we focus on tasks where hypotheses to be tested are given by the experimenter and not related to the identity or beliefs of participants.
Our main goal is to document how these tasks might relate to one another, and whether they could rely on a common underlying process. To do so, we use an individual differences approach and a multitrait–multimethod framework (MTMM; Campbell & Fiske, 1959). It is worth noting that few studies on confirmation bias followed an individual differences approach and most of them focused on myside bias (e.g., Stanovich et al., 2013). Rassin (2008) introduced a self-report measure of confirmation proneness; however, composite scores from various single item behavioral tasks (e.g., 2-4-6, interviewee) used as a criterion showed poor reliability.
We measure in each individual the three different cognitive components of confirmation bias described in prior research (i.e., information search, weighing of evidence, and memory recall) using three different experimental paradigms that have been most influential in the literature (the Wason selection task, 2-4-6 task, and interviewee task). We expect that different measures of the same component would be correlated across paradigms, indicating that this cognitive component can be robustly estimated at the individual level using different methods. The correlation of confirmation bias scores across components, on the other hand, will indicate the extent to which these components should be treated as distinct aspects of confirmation bias or whether this phenomenon can be considered unitary. Finally, we investigate how these aspects of confirmation bias relate to relevant societal issues using individual measures of dogmatism, pseudo-scientific beliefs, and conspiracy beliefs.