In this empirical study, we investigate an early childhood education activity in mathematics on the concept of 'pattern'. The children participating in the study attend an intermediate form of schooling in Sweden called 'the preschool class for six-year-olds', intended to facilitate their transition from preschool to school. Following a prolonged activity over 45 minutes, we analyse for what the children are supported in discerning and what they give as evidence of having discerned in and about patterns. The theoretical point of departure is variation theory, conceptualising learning as increased discernment. The results show that in terms of the important Vygotskian distinction between 'pseudo concepts' and 'concepts (proper)', the children's discernment and what they are supported in discerning are of the former kind. Pseudo concepts are discussed as integral to the institutional form of the preschool class and premised to be important to the child's further conceptual development. (author abstract)