Since that time the structured interview has evolved into a way of framing a dialogue between the student and the instructor in which the student is asked to talk freely about a concept or topic and/or to perform some task while thinking aloud. It has become the qualitative method most widely used to explore how students understand natural phenomena.

Many have found that structured interviews are sufficiently valuable to justify the amount of time and labor they can require. Because they allow students to express what they know and how they apply that knowledge in their own words in, they offer insights not typically obtained by other methods (Southerland, Smith & Cummins, 2000; White & Gunstone, 1992). Such interviews can allow instructors to develop subtle insights of students' conceptual understandings that have been shown to be very useful in planning and refining instruction (Bishop & Anderson, 1990; Lewis & Linn,1994).

Many studies have been conducted using structured interviews to describe students' conceptual knowledge and how that knowledge is applied in the "real world." Studies to date have employed a great variety of interview types including: interviews about instances (White & Gunstone, 1992; Demastes-Southerland, Good & Peebles, 1995a), prediction interviews (Demastes-Southerland, Good & Peebles, 1995a, 1996; Smith, 1992) and problem-solving or process interviews (Fredette & Clement, 1981; Lewis & Linn, 1994; Smith & Good, 1984).

Unfortunately, there is very little research comparing knowledge of student understanding generated by traditional examinations and the picture generated from structured interviews. In a study that compared descriptions generated through a variety of probes, Demastes-Southerland, Good & Peebles (1995b) determined that the results of prediction interviews were consistent with students' performance on traditional testing measures. Interviews about instances and word sorts, however, were found to generate portraits of a learner's understanding that were very different from those generated by exam responses.

In recent years many researchers have come to the conclusion that the most complete view of a student's conceptual understanding is probably obtained by using a combination of both qualitative methods (such as interviewing) and more traditional quantitative methods (such as traditional multiple choice exams) where the choice of the particular form(s) of each is tailored to fit the research question. Studies that employ multiple research probes have a high mode validity and are more likely to fully and adequately represent a learner's understanding (Songer & Mintzes, 1994; White and Gunstone, 1992).