The causes of difficulty in children’s creation of informal programs

We present a theory of the causes of difficulty in children’s creation of informal programs. Ten-year-old children are able to devise such programs to rearrange the order of the cars in trains on a simple railway track with a single siding. According to the theory, they rely on kinematic mental models that simulate the required sequence of steps, and we devised a computer program, mAbducer, which does so too in creating its own programs for such rearrangements. An experiment showed that a simple measure of the complexity of its programs, based on Kolmogorov complexity, predicts ten-year-olds’ difficulty in this task: the measure is the number of words in mAbducer’s programs for solving the rearrangement in a minimal number of moves. Complexity, in turn, reflects the structure of the required programs, which need loops of moves to be repeated, and often moves before and after such a loop. Children’s errors are predictable in both their location and nature. Our results therefore have implications for the assessment and pedagogy of computational thinking.