Since no one has mentioned it yet, it is important to note that this 2006 unpublished study has been retracted. The retraction can be found by the original authors in the paper "Mental models, Consistency and Programming Aptitude" (ACE 2008). They conclude that: Two years ago we appeared to have discovered an exciting and enigmatic new predictor of success in a first programming course. We now report that after six experiments, involving more than 500 students at six institutions in three countries, the predictive effect of our test has failed to live up to that early promise. So that's that.