Abstraction is considered an essential aspect of computational thinking. Primary schools are starting to include computational thinking into the curriculum. However, in order to guide their support, teachers need to know how to recognize abstraction. In this paper, we present how we can observe abstraction in young children tasked with solving an algorithmic assignment. In order to operationalize abstraction, we have used the layers of abstraction (LOA) model by Perrenet, Groote and Kaasenbrood. This model was originally used in the field of computer science and describes programming behavior at the level of software development, but has since been extended for use in primary education. We have operationalized this model for use with 5 to 6 year old students tasked with programming an educational robot. Their behavior has been related to each of the four layers of abstraction.