Background: We have previously presented two educational interventions aimed to diminish causal illusions and promote critical thinking. In both cases, these interventions reduced causal illusions developed in response to active contingency learning tasks, in which participants were able to decide whether to introduce the potential cause in each of the learning trials. The reduction of causal judgments appeared to be influenced by differences in the frequency with which the participants decided to apply the potential cause, hence indicating that the intervention affected their information sampling strategies. Objective: In the present study, we investigated whether one of these interventions also reduces causal illusions when covariation information is acquired passively. Method: Forty-one psychology undergraduates received our debiasing intervention, while 31 students were assigned to a control condition. All participants completed a passive contingency learning task. Results: We found weaker causal illusions in students that participated in the debiasing intervention, compared to the control group. Conclusion: The intervention affects not only the way the participants look for new evidence, but also the way they interpret given information. Teaching implications: Our data extending previous results regarding evidence-based educational interventions aimed to promote critical thinking to situations in which we act as mere observers.