The problem I was interested in exploring was the influence of different kinds of questions on the students’ behaviour. By carrying out an investigation, I obtained some understanding of how to encourage students to think critically and ask their own questions.

In 2001, I performed two experiments, denoted by S1 and S2 as described below, to study how students responded when asked different types of questions. About seventy students at Level 2 were involved in the two experiments. Since there are many concepts in physics that are not easy to understand for students, I selected two such concepts for the two experiments. The process of the experiments and the results are as follows.

S1 consisted of two steps. First, various aspects of a concept were explained; most of the students responded by just accepting what was taught without any queries. Next, the students were questioned about how the concept taught is possibly related to other concept(s); the students thought for a while and a few subsequently offered their answers.

It was observed that most of the students did not find it easy to grasp the spirit of the concept although they could repeat most of its properties and relate it to other concept(s). Upon further analysis, I realised that the students did not understand why the concept had been introduced, (i.e. the situation in which the concept had been introduced). Such knowledge is extremely important for one to understand difficult concepts. These observations prompted me to conduct the second experiment.

S2 consisted of three steps:

1. I explained to the students the background knowledge, in particular, an old theory, which are useful in introducing the concept.
   
   
2. I presented some new phenomena that could not be explained by the old theory, then, asked the students: “How would you improve the theory to explain the new phenomena?” The students responded by giving some suggestions.
   
   
3. I followed up on the students’ suggestions and discussed the possible results. Finally, I introduced the concept. The students responded by raising more suggestions. Then, some of the students even began asking why some of the suggestions could not work.

The teaching method used in S2 was successful in arousing the students’ curiosity about the phenomena surrounding the concept and helping them to understand why a new concept had to be introduced in the face of unexplained phenomena. It is important for students to cultivate such knowledge and ability if they wish to pursue a career in research. The S2 method also challenges the lecturer: the lecturer must have wide-ranging knowledge and a strong analytical ability to cope with the students’ suggestions in Step 3. Note that the lecturer should not just declare that a student’s suggestion as unfeasible; instead, he/she must take the time to explain why it cannot work.

To conclude, I wish to highlight that both S1 and S2 have their own advantages and one should not simply assume that S2 is better than S1 by the experiments explained above. S1 may be better for explaining concepts that are not counterintuitive because it is more systematic than S2 and takes less time. In contrast, S2 is suitable for explaining concepts that seem counterintuitive, or not obvious at the first sight.