Background: The study of myths in psychology has conceptual and educational relevance: How to adapt the teaching of psychology to confront myths with grounded knowledge? A first step is to know which myths prevail and its relation to training in psychology. Objective: To explore myth's prevalence among Spanish first-year university students of Social (SS) and Engineering Sciences (ES) (Study 1), and among different levels of expertise in psychology (Study 2). Method: Questionnaire including 21 myths. Study 1: 175 first-year SS and ES undergraduates. Study 2: 102 lay, semi-experts and experts in psychology. Results: Lower prevalence of myths among Spanish students than in other countries (approx. 37% vs. 60%), with SS students performing better than ES students. Experts performed significantly better (14% myths endorsed) than lay students (33%), but not than semi-experts (19%). Conclusions: The lower prevalence of myths compared to other countries may be due to methodological and sociocultural aspects. University training in psychology helps to better identify myths but does not eradicate them. Teaching Implications: Need to reflect on the little progress beyond a medium level of expertise. Teachers and students must identify their own myths and work on them in classroom, promoting critical thinking.