Abstract
The purpose of this research is to investigate the impact of a foreign language on the causality bias (i.e., the illusion that two events are causally related when they are not). We predict that using a foreign language could reduce the illusions of causality. A total of 36 native English speakers participated in Experiment 1, 80 native Spanish speakers in Experiment 2. They performed a standard contingency learning task, which can be used to detect causal illusions. Participants who performed the task in their native tongue replicated the illusion of causality effect, whereas those performing the task in their foreign language were more accurate in detecting that the two events were causally unrelated. Our results suggest that presenting the information in a foreign language could be used as a strategy to debias individuals against causal illusions, thereby facilitating more accurate judgements and decisions in non-contingent situations. They also contribute to the debate on the nature and underlying mechanisms of the foreign language effect, given that the illusion of causality is rooted in basic associative processes.
Keywords
In daily life, people have to make critical decisions with no room for errors. For instance, politicians need to select the best economic policies, a Wall Street broker must make fast financial decisions, or a general practitioner must judge which one is the best treatment or recommendation for a patient. These examples have something in common. In all three cases, people have to evaluate cause–effect relationships to make the best decision possible. Furthermore, in a world where hundreds of millions of people use a foreign language on their daily lives, it is probable that the politician, the broker, or the general practitioner has to make these decisions in a foreign language. Although people are usually able to assess causal relations quite accurately (Jenkins & Ward, 1965; Shanks & Dickinson, 1987; Wasserman, 1990), it has also been well established that, under certain circumstances, people tend to infer a causal relationship when there is none, giving rise to a cognitive bias known as the causal illusion or the illusion of causality (see, for example, Matute et al., 2015; Vadillo, Blanco, Yarritu, & Matute, 2016). Would this illusion be affected by whether they have to make the judgement in a foreign language? The aim of the present research will be to study the impact of a foreign language on the illusion of causality.
The illusion of causality consists of overestimating the degree of causality between two events, or even believing that two events are causally related when they are not. This bias has serious implications in that it promotes decisions which are based on illusory causal relationships. For instance, people may think that a bogus medical treatment is helping them recover from a certain health problem. This may cause even death, as it may prompt people to not go to the hospital when they need it (Freckelton, 2012). Similar problems can be found not only in health-related areas but also in relation to many other life events. Indeed, previous findings support the idea that the illusion of causality underlies, at least in part, social problems such as financial bubbles (Malmendier & Tate, 2005), social stereotypes (Crocker, 1981; Murphy, Schmeer, Vallée-Tourangeau, Mondragón, & Hilton, 2011), gambling (Orgaz, Estévez, & Matute, 2013), pseudoscience (Matute, Yarritu, & Vadillo, 2011), superstitious thinking (Blanco, Barberia, & Matute, 2015), or the use of alternative medicines (Blanco, Barberia, & Matute, 2014).
Interestingly, other cognitive biases, different from the illusion of causality, have been shown to be affected by the language in which the information was presented. Keysar, Hayakawa, and An (2012) reported that thinking in a foreign language not only changed the decisions that people made but also that these decisions were more systematic and normative. Their experimental participants were less affected by the loss aversion bias when they made decisions in a foreign language. Keysar and his colleagues called this effect the foreign language effect. Costa, Foucart, Arnon, Aparici, and Apesteguia (2014) replicated the effect on the loss aversion bias in a different population and using both the same problem as Keysar and colleagues (a modified version of the
A cognitive bias can be defined as a systematic deviation from a rational norm in judgement or decision-making. The inference of causality relies on the assessment of the contingency between the potential cause and the outcome (Baker, Murphy, Vallée-Tourangeau, & Mehta, 2000; Cheng, 1997; Shanks, 2010; Shanks & Dickinson, 1987; Wasserman, 1990). Thus, in causal learning situations, a bias can be defined as a systematic deviation of causality judgements from the actual contingency between the potential cause and the outcome. The most commonly used measure of contingency, the Δ
Fortunately, research on the field has identified many of the conditions that promote the overestimation of causality (Matute et al., 2015). People tend to infer causality from coincidences, giving special weight to the probability with which the outcome occurs in the presence of the cause (i.e., trials in which the potential cause and the outcome coincide, even by mere chance; see Jenkins & Ward, 1965; Kao & Wasserman, 1993) instead of taking into account all the information. The illusion of causality is strongest when the contingency is null but the outcome or the potential cause or both occur with high probability (Allan & Jenkins, 1983; Blanco, Matute, & Vadillo, 2013; Hannah & Beneteau, 2009; Matute et al., 2011; Perales, Catena, Shanks, & González, 2005; Perales & Shanks, 2007).
Although not the only theoretical account, most of the evidence that has been published on the illusion of causality supports the idea that people establish their causal judgements, whether accurate or illusory, through associative learning. Associative models of learning predict how causal estimates are progressively acquired as people gain experience with the potential cause and the outcome in a trial-by-trial basis. Variables that increase the formation and strengthening of cause–outcome associations favour the strengthening of causal judgements (whether real or illusory), whereas variables reducing the formation of associations weaken the judgements of causality (whether real or illusory) between a potential cause and an outcome (Baker et al., 2000; Matute et al., 2015; Shanks & Dickinson, 1987; Vadillo et al., 2016).
Simulations of one of the most popular associative models of learning, such as the Rescorla and Wagner model (1972), have been conducted that accurately predict the results of many experiments on the illusion of causality (see Matute et al., 2015; Vadillo et al., 2016). These models predict that variables such as the probability with which the potential cause occurs and the probability with which the outcome occurs will have a significant effect on the illusion of causality. As mentioned above, this result has been confirmed in many experiments showing that the illusion of causality increases when either the probability of the cause or the probability of the outcome, or both, is high (e.g., Allan & Jenkins, 1983; Blanco et al., 2013). Moreover, other variables that are known to influence associative learning, such as, for instance, the existence of alternative potential causes, have also been found to affect the development of causal illusions (Vadillo, Matute, & Blanco, 2013). In sum, there are reasons to believe that the process underlying causal illusions is associative in nature. Nonetheless, and although the mechanisms of how the illusion of causality arises seem to be clear, research on how to reduce these errors has been scarce, as it has been the case with most other cognitive biases (Lilienfeld, Ammirati, & Landfield, 2009).
The accumulated evidence on the foreign language effect suggests that the use of a foreign language promotes more normative responses under certain conditions, supporting an increased-systematicity account (Keysar et al., 2012). The underlying mechanism, however, remains unknown. The tendency to be more normative when using a foreign language could be explained in principle by a greater psychological distance, by cognitive disfluency, or by a reduction in the emotional impact, which is currently the leading explanation of the effect (Hayakawa, Costa, Foucart, & Keysar, 2016). Furthermore, it is also possible that these accounts are not incompatible, and a possibility exists that some of these processes, such as the proposed reduction of cognitive fluency, could also weaken the strength of the acquired associations, thereby reducing the causality bias. In any case, it seems that the use of a foreign language could provide an effective and interesting strategy to reduce other biases, such as the illusion of causality, in which decision-making and judgements are involved.
Thus, taking into account that presenting the information in a foreign language effect has proven effective in reducing many different types of biases (one of them the
Thus, given the potential relevance of this line of research, in the present experiments, we aimed to reduce the illusion of causality through a manipulation that has proven to improve accuracy and to promote more systematic and normative responses in other decision-making problems (i.e., the foreign language effect). Furthermore, our experiments aim to contribute to the discussion on the potential explanations of the effect, since the illusion of causality is rooted in associative principles and is not, at least in principle, an emotional grounded bias. We hypothesised that participants who performed a non-contingent task in a foreign tongue will show a significant reduction of this bias.
Experiment 1
Method
Participants
In total, 36 exchange students (27 women, mean age 20.5 years) volunteered for this experiment. They were all English native speakers, and they were studying Spanish as a foreign language at the University of Deusto. They started to learn Spanish at a mean age of 13 years, mainly in a classroom environment. All volunteers gave their informed consent and were rewarded with €6.
Materials
The materials consisted of a pencil and paper booklet and a standard causal learning task, specifically, a computerised version of the allergy task (Matute et al., 2011; Wasserman, 1990). Although the participants were attending to similar linguistic level classes and were randomly assigned to the experimental conditions, we wanted to ensure that there were no significant differences between groups in some critical variables. Therefore, to test their language proficiency and cognitive ability, we asked participants to fill a booklet that included two self-assessment language tests, a foreign language comprehension test, and the
Procedure and design
The experiment was conducted across two sessions. In the first session, participants filled in the paper and pencil booklet. In the second session, they were randomly assigned to one of the experimental groups and performed the causal learning task on one of the computers in individual cabins in our laboratory. This second session was conducted entirely in the language of the group to which the participant had been assigned—either the native or the foreign language (Keysar et al., 2012). In this causal learning task, participants were instructed to imagine being a medical doctor who had to learn whether a fictitious drug called Batatrim (i.e., potential cause) was effective in the healing of the crises produced by a fictitious disease (i.e., outcome). On each trial, participants saw information about a fictitious patient (see Figure 1). In the first panel, they saw information on whether the patient had taken the drug or not (i.e., potential cause present or absent). Then the second panel contained a question in which participants had to guess whether that particular patient would feel better. Participants had to answer by clicking one of two buttons, “

Screenshot of a training trial. In the upper panel, participants saw information about the presence or absence of the potential cause. The middle panel shows the predictive question that was used to maintain their attention. Once participants gave their response, the program showed the lower panel with information about the presence or absence of the outcome.
After 40 trials (one per patient), participants were asked to give a causal judgement by answering the question “
The design summary is shown in Table 1. Two groups of participants saw patients who had taken a drug that was non-contingent with the healing of the crises, one group in their native tongue (
Design of the experiments.
Experiment 1 used only the two Non-contingent groups and was conducted with native English speakers. Experiment 2 used all four groups and was conducted with native Spanish speakers. C (potential cause) is a fictitious drug. O (outcome) refers to the healing of the crises produced by the fictitious disease.
Results and discussion
Before looking at the critical results, that is, the causal judgements, we checked whether there were base-level differences in language proficiency and in cognitive ability. Mann-Whitney tests showed no significant differences between the native and the foreign group on the self-assessment scales, for the native language (
Language proficiency and cognitive ability in participants from Experiment 1.
NL: Native Language; FL: Foreign Language; CRT: Cognitive Reflection Test;
Most importantly, participants who performed the task in their foreign language perceived the drug as less effective than those who performed the task in their native tongue (see Figure 2). This was confirmed by a one-way analysis of variance (ANOVA), which yielded a significant main effect of language,

Mean judgement of causality for Experiment 1 (left panel) and Experiment 2 (right panel). Experiment 1 was conducted with native English speakers, and Experiment 2 with native Spanish speakers. Error bars depict the 95% confidence intervals for the means.
One might argue that since the native tongue was always English and the foreign one was always Spanish, the linguistic distance between the two languages and/or some linguistic peculiarities of each one could perhaps influence the results. Therefore, we considered that a second experiment replicating this study with Spanish native speakers was required. In addition, it is possible that participants in the foreign group might experience linguistic problems, and might be more prudent when emitting their judgements (which would lead to a lower judgement and an apparent attenuation of their bias). To address this issue, in Experiment 2, we added two contingent groups that saw a drug that actually worked. Thus, these two groups served as a control condition. If the results of Experiment 1 were due merely to a general reduction in the judgements when using a foreign language, then we should expect a reduction in the judgements even in the contingent task when performed in the foreign language. However, if the foreign language only affects the evaluation of causality in situations that are prone to the illusion of causality (i.e., non-contingent), then the participants of the contingent groups should give a positive and rather accurate judgement, regardless of whether they were assigned to the group performing the experiment in the foreign or native language. Therefore, in a cross-linguistic experiment, we expect to replicate the foreign language effect that we found in Experiment 1 in the non-contingent groups of Experiment 2. We also expect no such effect in the judgements of the contingent groups. This would indicate that the reduction in the responses is indeed a reduction of the illusion of causality rather than a general reduction of judgements.
Experiment 2
Method
Participants
In total, 80 Spanish native speakers (49 women, mean age 23.8 years) volunteered for this experiment. They started to learn English at a mean age of 7 years, mainly in a classroom environment. All of them were students at the University of Deusto and were enrolled on English courses when they performed the experiment. All volunteers gave their informed consent and were rewarded with €6.
Materials
In this experiment, we used the same materials as those employed in Experiment 1—a pencil and paper booklet, and a standard causal learning task. As in the previous experiment, the two self-assessment tests and the CRT were written in the participants’ native language (i.e., Spanish), and the comprehension test in the foreign language (i.e., English). The CRT (originally in English) was translated and back-translated by bilingual speakers (Brislin, 1970).
Procedure and design
We followed as closely as possible the procedure of Experiment 1. Thus, the study was conducted across two sessions. During the first session, participants were asked to fill in the paper booklet. During the second session, they were asked to perform the causal learning task in individual cabins in our laboratory. As in Experiment 1, the second session was conducted entirely in the language to which the participant had been assigned (Keysar et al., 2012). The design of the experiment is shown in Table 1. In this experiment, the two non-contingent groups (native language,
These contingent groups were used just as an additional control. Their purpose was to ensure that the expected reduction of the illusion of causality in the foreign language group exposed to non-contingent events was not due to a general reduction of their judgements due to prudence, or other artefacts when using the foreign language. Therefore, we expected all participants in the positive contingent conditions to accurately perceive that the two events were causally related, thereby approximating their causal judgements to the actual contingency between the two events (i.e., Δ
Results and discussion
We first assessed possible base-level differences in language proficiency and cognitive ability. Mann-Whitney tests comparing the native with the foreign groups yielded no significant differences between them on the self-assessment scale for the native language (
Language proficiency and cognitive ability in participants from Experiment 2.
NL: Native Language; FL: Foreign Language; CRT: Cognitive Reflection Test;
The critical results for this experiment are shown in Figure 2, which depicts the mean judgements of causality for each of the four experimental groups. As expected, in the contingent groups, both the native and the foreign language groups perceived the drug as moderately effective (i.e., in accordance with its actual Δ
This was confirmed by a 2 × 2 (Language [native, foreign] × Contingency [non-contingent, contingent]) between-groups ANOVA.
1
This analysis revealed a significant main effect of contingency,
General discussion
The two experiments presented here show that both the foreign language and the native language groups developed some degree of causality bias. However, when participants performed the task in the foreign language, they were significantly more accurate in their assessment of the null contingency in both Experiment 1 and Experiment 2. That is, as we expected, the illusion of causality was replicated in both experiments, and in both cases, the use of the foreign language reduced the strength of this bias. This is of important applied and theoretical value.
But before discussing the applied and theoretical implications of these results, it is worth noting that, given that in both experiments participants were enrolled in the same proficiency level class of their foreign language and that all of them successfully translated one trial verbally at the end of the experiment, it appears that language proficiency in the foreign language did not hinder their understanding of the task. The lack of statistical differences between the foreign and the native groups in their language proficiency and their CRT scores indicates that the differences in their judgements in the null contingency condition cannot be attributed to differences in language skills or cognitive ability. In addition, both groups judged the contingent condition of Experiment 2 accurately, adjusting their judgements to the actual contingency between the two events (i.e., Δ
At first glance, the lack of statistical differences between the two contingent problems (non-contingent vs contingent) in the native language condition in Experiment 2 might seem problematic. As previously mentioned, however, this is a common result in the illusion of causality literature (see, for example, Matute et al., 2011). Appreciate that (a) the contingent problem was positive but not very high (i.e., Δ
Thus, taken together, the results of both experiments support our hypothesis that using a foreign language helps people reduce their illusion of causality. These findings imply that presenting the information in a foreign language when making a causal inference could be used as a strategy to reduce the causality bias without manipulating the information about the potential cause and outcome. Reducing the probability of the cause and/or the probability of the outcome is a strategy that is known to be effective in reducing the illusion (Allan & Jenkins, 1983; Blanco et al., 2013; Hannah & Beneteau, 2009; Matute et al., 2011; Perales et al., 2005; Perales & Shanks, 2007) but cannot always be used. Using a foreign language could therefore prove to be a very useful strategy in real-life situations in which the probability of the cause and/or the outcome remain uncontrollable. Recall that the illusion of causality occurs precisely in situations in which either the cause or the outcome or both of them occur frequently but independently of the participants’ behaviour (see Matute et al. (2015) for review). Thus, the important practical implication is that using a foreign language to reduce the causality bias could lead to better decision-making in many situations in which the probability of the potential cause and the outcome are given and, therefore, uncontrollable to the decision-maker.
Importantly, the results of the present research not only add to the growing body of evidence for the foreign language effect but could also shed some light on the relevant underlying mechanisms. As in other studies on the field, our experiments show a reduction in a particular bias when the task is performed in a foreign language. Therefore, our data support the
One possible mechanism to explain the effect is that the foreign language increases psychological distance to the problem which, in accordance to construal-level theory, would give people a more abstract representation, relying on schematic, prototypical information (Fujita, Henderson, Eng, Trope, & Liberman, 2006). In the last term, this high level of abstraction would lead people to pay more attention to ends over means (Hayakawa et al., 2016). This hypothesis fits very well with the evidence that has been reported using moral dilemmas, where participants tended to be more utilitarian when they performed the task in a foreign language.
Another potential explanation, proposed by Keysar et al. (2012), claims that thinking in a foreign language increases the emotional distance, which leads to a reduction in emotional resonance (Keysar et al., 2012; Pavlenko, 2012). Given that the decision-making tasks that they used in their experiments involved risks and losses, it makes perfect sense to assume that reducing the emotional component may alleviate this kind of decision-making bias. Actually, this is the current leading account to explain the foreign language effect (Hayakawa et al., 2016).
The last
The aim of our experiments was not to discriminate between the different theoretical accounts of the foreign language effect, and therefore, they were not designed to meet this purpose. Likewise, different experiments should have been conducted if our purpose would have been to test the potential explanations of the causality bias (see Matute et al. (2015) for discussion on potential explanations). Thus, our results should be interpreted with caution in relation to their support of the different potential explanations. However, it is worth highlighting some interesting features of our experiments. In the present research, we observed the foreign language effect in a passive, trial-by-trial causal learning task, which means that participants were exposed to mere observational, vicarious information. That is, participants did not have to decide whether they administered the medicine to their fictitious patients, as is the case in some other versions of this task (see Yarritu, Matute, & Vadillo (2014) for discussion on passive vs active tasks). In our version of the causal learning task, the life of the fictitious patients did not rely on the participants’ decisions, that is, participants were mere observers. Thus, at least in principle, we believe it is difficult to argue that our experiments involved any emotional component or that they might involve different levels of psychological distance. Furthermore, the causality bias is rooted on basic, associative learning mechanisms, and has been observed regardless of the level of personal involvement of the participant (Matute et al., 2015; Yarritu et al., 2014). This suggests that different levels of psychological distance and emotionality are not, at least in principle, critical factors in the development of this effect. It could be argued that, because to maintain attention we asked participants to answer a predictive question on each trial, the information presented immediately after they responded about the occurrence of the outcome could evoke some emotional reaction. However, when asked to provide some informal feedback upon finishing the experiments, the participants, if anything, tended to mention boredom, rather than emotionality. In addition, the financial reward for participating in the experiment did not depend on their performance, so we believe this indirect feedback could hardly be associated with any relevant emotion, as it is not suggesting that they were performing better or worse. Indeed, we believe that participants simply attend to this feedback and attempt to learn from it, in accordance with the goal of the task as stated in the instructions. They were not asked to heal as many patients as possible, as in other versions of the task, but to learn whether the drug was effective.
We believe our results are more compatible with the processing fluency explanation. Processing fluency affects all kinds of judgements (see Song & Schwarz, 2010). Some researchers suggest that fluency operates directly (Schwarz, 2004). That means that regardless of the information that is being transmitted, if it is presented disfluently, people will infer that the information is less familiar and that the task is more difficult to accomplish (Song & Schwarz, 2010). As previously mentioned, it has also been suggested that processing fluency can affect the selection of processes involved in the resolution of a task, activating deliberative and analytical processes (Alter et al., 2007; Gervais & Norenzayan, 2012; Oppenheimer, 2008). This hypothesis is supported not only by the improvement in reasoning tasks when the information is presented in a disfluent font (Alter et al., 2007) but also by the reduction of cognitive biases such as the
Footnotes
Declaration of conflicting interests
The author(s) declared no potential conflicts of interest with respect to the research, authorship, and/or publication of this article.
Funding
Support for this research was provided by Grant PSI2016-78818-R (AEI/FEDER, EU) from Agencia Estatal de Investigación of the Spanish Government, and the European Regional Development Fund, as well as Grant IT955-16 from the Basque Government, both awarded to H.M. The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the article.
