It is important to understand how users can utilize database systems more effectively to enhance performance. A major research interest is to evaluate and compare user performance across different data models and query languages. So far, experiments have tested combinations of model plus language. An interesting theoretical and practical question is: how much of the performance difference is caused by the data model itself, and how much by the additional query language syntax? A cognitive model of query processing suggests measurement at two stages. The data model has impact at the first stage, and the model with the query language syntax together has the impact at the second stage. An experiment that compares the objected-oriented and relational models and query languages at the two stages provides fresh results.