When good results mislead: How positive student outcomes lead teachers to overestimate the effectiveness of their assistance

• High base-rates of positive outcomes erroneously increase teachers’ beliefs in the efficacy of their advice. • Outcome density influences perceived efficacy of both emotion regulation and maths performance advice. • Results highlight the need for scientific literacy and bias awareness in teacher training. Teachers play a vital role in shaping both the emotional and academic outcomes of their students, yet their judgments about the efficacy of the strategies they use to help students may be susceptible to cognitive biases. This study investigates how the base rates of educational outcomes, including student affect and performance, can create causal illusions in teachers' efficacy beliefs. In two experiments, teachers were instructed to provide advice to a fictitious student completing math problems. In Experiment 1, teachers were informed about the student's affect, while in Experiment 2, they were informed about the student's accuracy on the math problems. In both experiments, no contingency existed between the teacher’s advice and the outcomes; that is, their advice did not affect the probability of the student feeling good or getting the math problem correct. However, teachers in the high base-rate conditions, where the student, on average, felt good or performed well on the math problem, consistently reported that their advice was effective, despite the absence of any actual causal effect on student outcomes. Teachers in the low base-rate condition rated their efficacy significantly lower than those in the high base-rate conditions, and these ratings did not differ from zero for emotion regulation efficacy. These findings underscore how base rate effects can misalign teachers’ efficacy judgments and suggest that teachers may need additional support and training to help them accurately judge the effectiveness of their actions.