Changing conceptions with an "intelligent tutor"

This paper reports results of a study of students' learning of qualitative physics concepts while using the intelligent computer-based instructional (ICBI) program, Freebody (Oberem, 1996). Students' force and motion conceptions, which underpin their ability to construct free-body diagrams (abstract representations of forces acting on an object), were assessed before and after use of the program. The program helped students to confront inconsistencies in their reasoning about Newtonian physics but results suggest that new knowledge was about classifying the context rather than conceptual change.

Introduction

An 'intelligent' tutoring program actively builds up a picture of its user and adapts or designs instructional strategies to meet their ever-changing needs and proficiency. Such a program consists of three 'models', the Expert Model, Student Model and Instructional Model. The Expert Model contains a database of relevant subject-based knowledge. The Student Model contains the framework for identifying a user's misconceptions and sub-optimal performance. It contains a database of misconceptions and missing conceptions. A missing conception is an item of knowledge which the expert has but the student lacks; a misconception is an item of knowledge that the student has but the expert lacks. The Instructional Model contains the program's pedagogical strategies.

Background

Conceptual change may occur following student's realisation that their existing beliefs can longer satisfactorily explain their observations, and provided that a new belief is plausible and proves fruitful is its further application (Hewson, 1981). The process of disequilibration in which the learner realises that beliefs do not match observations is characterised by both rational and emotional responses (Gorsky & Finegold, 1994). Several researchers have attempted to describe the nature of conceptual change, from students' development of synthetic models (Vosniadou, 1994) to change resulting from ontological changes in concepts (Chi, Slotta & DeLeeuw, 1994 ; Dykstra, Boyle & Monarch, 1992; Thagard, 1992).

Earlier research (Yeo, Loss, Zadnik, Harrison & Treagust, 1998) with students learning conceptually difficult physics using an interactive multimedia program, found that students proceeded too rapidly through the program, often ignoring instructions and key details. It was suggested that students placed their own, often incorrect, interpretations on what they looked at and ignored that which contradicted their prior conceptions. Although learner control is increasingly favoured in educational multimedia programs, user control in this example enabled users to avoid confronting and/or resolving their incorrect alternative conceptions.

Aim

Method and data collection

Subjects
The study involved 58 students, 26 females and 32 males, from five different classes, four at high school and one at university. All school students (N=59) were in Year 12 Physics classes and had studied physics in Year 11. The university students (N=5) were studying a service physics unit and had less formal physics backgrounds. Most students worked in pairs.

Pretest and posttest
The pretest/posttest was developed from a force-concept inventory, originally produced by Hestenes, Wells and Swackhamer (1992), and described by Mazur (1997). The selected items were modified: some contexts made more familiar to local students, the multiple choice format modified requiring students to agree or disagree with each of a number of statements about a given context and students asked to give a written explanation for some answers. There were 45 questions in 19 different items, 26 about identifying forces acting in given situations and 19 about the relationship between force(s) and motion.

Other data
The software recorded all student/computer interactions and dialogue in a text-based 'user history'. In addition, four pairs of students were videoed so that their spoken dialogue and physical interactions with the program were recorded simultaneously with the computer screen, on a picture-in-picture videotape image.

Procedure
Prior to using the program, each student completed the pretest and then after the program were given the same questions as a post-test. Students took about 25 minutes to complete each test. Most had 75 minutes to work on the program, although Group 3 students had only an hour. Not all students completed the 10 Freebody exercises.

Results

The Spearman-Brown coefficients for pretest and posttest were 0.89 and 0.84 respectively suggesting that the test was a reliable measuring instrument.

Discussion

The instructional design of the program adopts a constructivist rather than instructivist approach, discussing students' ideas with them and encouraging them to resolve inconsistencies or contradictions in their beliefs. Two students, Sam and Adam (S&A), had difficulty with Exercise 8, which shows a boy having thrown a rock in the air. They (incorrectly) drew an upward 'propelling' force on the rock. Freebody (C) suggested they consider an inconsistency in their reasoning.

C:	What kind of force is force #1?
S&A:	Normal force
C:	What exerts this normal force?
S&A:	Boy
C:	On what is this force being exerted"
S&A:	Rock
C:	A normal force is a contact force. The boy is not in contact with the rock. Can the boy exert a normal force on the rock?
S&A:	No
C:	So what is exerting this normal force which you drew?
S&A:	Boy
C:	A normal force is a contact force. The boy is not in contact with the rock. Can the boy exert a normal force on the rock?
S&A:	Yes
C:	I don't see how this can be. A contact force implies contact between the objects.

Sam:	There has to be another force.
Adam:	I don't reckon there is another force.

Why did Sam and Adam eventually delete the 'upward' force? Either because there was nothing which could exert a force upwards or because it became the only solution to the dilemma that they faced. If the former, it represents an important cognitive step. If the latter, it may simply be a rote-learned response for the particular context, and not necessarily transferable to another context. Four questions in the pretest/posttest examined the alternative conception: force of motion (A moving object has a 'force of motion' in it. A body slows down and stops as its force is used up. McCloskey, 1983). These two students were incorrect on two of the four questions which directly tested for this conception on the pretest but were correct for all four on the posttest.

Such incidents lead to an examination of sets of questions which examined a single concept or conception. The following describes one such group of three questions.

Questions 13 and 14 were about identical situations; an aeroplane flying at constant speed and height. Question 13 provided a diagram of an aeroplane and showed four balanced forces, thrust, drag, weight and lift; part 13C asked if the velocity of the plane was constant. Question 14 referred to a text description of an aeroplane with motion consistent with the diagram in Question 13. Part 14A asked if the net force acting on the plane was zero. Question 19 gave a situation of constant speed under the effect of several forces - a person pushing a box at constant speed. Part 19A asked if friction was less than the [forward] applied force. In effect, Questions 13C, 14A and 19A were all based on equivalent situations - a body moving with constant speed. The number of students who answered correctly are shown in Table 3.

An explanation for the variation in pretest results is that students have learnt to recognise the diagram used for Question 13C, that of a vehicle having four balanced forces moving at constant speed, and most answered using a rote-learned response. Students learn to apply Newton's first law in similar contexts. It appears that many students did not recognise that Question 14A applied to an identical situation as Question 13C and so applied naive reasoning, most probably a common alternative conception: A constant force acting on a body produces a constant speed (McCloskey, 1983). Why then, did only six students answer Question 19A correctly since it was (as far as physics principles are concerned) similar to Question 14A? We suggest that, unlike Question 14A, fewer students had encountered the context for Question 19A and hence the context was treated by most with intuitive reasoning alone.

Following use of Freebody, all students correctly answered 13C and there was an increase of 20 answering 14A correctly. It is likely that many of these students came to see that Questions 13C and 14A referred to identical situations. Nevertheless, 19 students still used their original force-motion conception for Question 14A despite answering Question 13C correctly. Very few students changed their minds about Question 19A.

Many students held conflicting conceptions, both before and after use of the program. This is explainable if a conception is inextricably linked to a context and does not exist without a context in which it applies. All of the students had studied Newton's laws and would have written or talked about their Newtonian understandings in textbook or teacher-generated contexts. It may be that the context itself is what students retain in memory, perhaps categorised as 'situations consistent with Newton's first law.' Only contexts which closely resemble those categorised thus will be recognised by students as ones to which Newton's first law applies. The limited improvement in Question 19A was possibly because most students still did not recognise the situation as one to which Newton's first law applies.

Two other groups of four questions also support the ideas developed here, that conceptual change is linked to students' learning about contexts. This study, therefore, suggests that in teaching conceptually difficult ideas, students need to become familiar with many applications of the conception as possible if they are to start to believe the universal applicability of the ideas.

Conclusion

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