Helping introductory physics students check for the validity of their responses**

A growing body of research suggests that many students need help to recognize how to apply relevant physics knowledge to check for the validity of their answers in situations that elicit intuitively appealing (but incorrect) ideas. We designed instructional interventions that consisted of two phases. In Phase 1, students completed a web-based assignment individually outside of class, and in Phase 2, this assignment was reviewed in class in an instructor-led discussion. The web-based assignments consisted of sequences of questions intended to guide students to re-examine their initial intuition-based responses and override them, if necessary, by applying formal physics knowledge. Results show that only a small fraction of the students (<20%) recognize and override mistakes in their initial responses. Most students (1) answer the intervention questions in a manner that supports their intuitive responses (i.e., confirmation bias) or (2) do not recognize and examine inconsistencies in their answers. After phase 2, however, about half of the students improved their performance on the assessment included in the test. The results suggest that many students need help building confidence in their physics knowledge and reasoning approaches.