  We discuss the effect of administering conceptual and quantitative isomorphic
problem pairs (CQIPP) back to back vs. asking students to solve only one of the
problems in the CQIPP in introductory physics courses. Students who answered
both questions in a CQIPP often performed better on the conceptual questions
than those who answered the corresponding conceptual questions only. Although
students often took advantage of the quantitative counterpart to answer a
conceptual question of a CQIPP correctly, when only given the conceptual
question, students seldom tried to convert it into a quantitative question,
solve it and then reason about the solution conceptually. Even in individual
interviews, when students who were only given conceptual questions had
difficulty and the interviewer explicitly encouraged them to convert the
conceptual question into the corresponding quantitative problem by choosing
appropriate variables, a majority of students were reluctant and preferred to
guess the answer to the conceptual question based upon their gut feeling.
