This paper deals with the competence of Cultural (epistemological, historical and anthropological) Analysis of the Content (CAC), which is important for teachers' awareness and autonomy when dealing with educational choices in a changing cultural and institutional context. We report on an 18-hour intervention in a teacher education course at the undergraduate level attended by 12 participants during the fall of 2013. The goal of the intervention was to enhance participants' CAC in the case of Elementary Arithmetic Theorems by using the rationality construct derived from Habermas' work. Qualitative analyses of participants' discussions showed how the construct was gradually appropriated by them and contributed to their CAC. Trends emerging from quantitative comparisons with previous implementations of the same course provided some evidence regarding the effects of the intervention on the quality of participants' CAC performances at the end of the course. The method chosen for participants' assessment and their cultural background will be discussed as conditions for the success of the intervention.