Research on factors affecting enrolments in science-related studies has constantly struggled with poorly conceptualized and developed measurement instruments. After discussing theoretical and psychometric properties pitfalls of the most relevant measures used in the Spanish science education literature, this study reports on the development and initial validation of an instrument rooted in the expectancy-value theory of achievement motivation, named SUCCESS. Content validity was established using a panel of experts, and item readability and interpretation was confirmed through cognitive interviews with the target sample. Besides, exploratory factor analysis resulted in a 6-item unidimensional scale of satisfactory construct and convergent validity. Finally, Cronbach α and item-total r provided acceptable evidence for internal consistency reliability, which supports its use in exploratory studies. This promising instrument can be used to advance research on factors affecting enrollments in science education careers from the early stages of the educational system.
