The aim of the study is to investigate how contrast of critical aspects of the object of learning could be used to improve children’s ways of discerning the mathematical concept twice as, by analyzing an learning study project in Swedish preschool. The empirical material consisted of verbatim transcriptions of a screening (n=24), three video-documented interventions, and 132 individual test forms (n=44) completed before and after a teaching activity and four weeks later. By letting different aspects related to the intended object of learning appear as variant or invariant, different patterns of variation were used in developing the interventions. The results shows differences related to the children's learning in each of the three cycles. It indicates that a conscious use of simultaneity and contrast of identified critical aspects seems successful in stimulating children’s short- as well as long-term learning. Thus, the results of the study suggest that variation theory can serve as a guiding principle in the development of pedagogical design in preschool. The study also indicates the need for more LS projects on the application of variation theory in preschool educational practice.