Research in Science Education, 1993, 23, 228-235

HOW CONSISTENTLY DO STUDENTS USE THEIR ALTERNATIVE CONCEPTIONS?

David Palmer The University of Newcastle

ABSTRACT

Existing research indicates that many students hold an alternative conception that "an object in motion must have a force pushing it along", but they do not apply this conception consistently to problems involving different types of motion. This project was designed to investigate the degree of consistency of student responses to questions concerned with linear motion. The results indicated that most students were unable to consistently apply either the alternative conception or the correct scientific response. The students appeared to have a general problem in recognising similarities between contexts, even when the contexts were closely related. The results also suggested that the responses of some studerits were influenced by contextual factors such as the nature of the moving body, the direction of the motion and the speed of the motion.

INTRODUCTION

Over the last two decades, a great amount of research has focussed on the alternative conceptions which students hold in relation to scientific concepts. In many cases, these ideas are quite different from the accepted scientific viewpoints and appear to be quite widespread. However, as Driver (1989) stated in her review of this subject : "One open question is the extent to which children's conceptions are genuinely 'theory-like', that is...being used consistently in different contexts."

One of the alternative conceptions which has been investigated for consistency is the idea that a moving body always has a force acting on it in the direction of the motion. Halloun and Hestenes (1985) found that about 40% of university physics students used this idea consistently when applied to linear and projectile motion. Finegold and Gorski (1991) tested university and high school students with questions concerning periodic, linear and projectile motion and found that "the motion implies a net force framework is not consistently applied". An important contribution has recently been made by Galili and Bar (1992) who designed a graded set of questions covering linear, periodic, circular and constant motion. They sampled high school and university students and found that pupils were more likely to use the "motion- implies-force" conception as the questions became less familiar. Thus, the data appear to indicate that this alternative conception is usually not consistently applied to different types of motion. We might predict that consistency would be higher if all the questions covered one, simple type of motion only. However, this still needs to be investigated.

Studies of consistency in other alternative conceptions in science have presented conflicting evidence. Vosniadou and Brewer (1989) studied conceptions of the Earth's shape, identifying "consistent concepts for the great majority of the children". However, Summers and Kruger (1992) found inconsistencies in their subjects' descriptions of energy, and Engel Clough and Driver (1986) reported that "students were using different alternative frameworks in response to parallel questions" on pressure, heat and inheritance. The latter authors noted the importance of the context (or setting) of the question in determining an individual's response. Some authors have successfully identified critical

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contexts which influence students' conceptions. For example, Whitelock (1991) and Fischbein, Stavy and Ma-Naim (1989) studied students' conceptions of motion and found that the type of moving body was an important factor for some.

The aims of this study were to investigate the degree of consistency of students' responses to questions solely concerned with linear motion, and to investigate the effect of context on consistency.

METHOD

The instrument

This study used a survey approach designed to identify broad trends in students' responses. The instrument consisted of a test entitled "Forces in Sport" containing 10 multiple choice questions which were selected after a pilot survey involving 72 university students. Two of the ten were distractor questions, not related to the investigation. The eight test questions (all of which are presented in the Appendix) concerned the direction of the force on a freely moving object in linear motion. They were written in simple language and described daily-life situations, and each was accompanied by a simple, line drawing to illustrate the problem. Each question had a scientifically correct response, one distractor which indicated that "motion-implies-force" (as used by Osborne & Gilbert, 1980, and Halloun & Hestenes, 1985), and two other plausible distractors.

To allow analysis of possible contextual effects the questions were systematically interrelated along three parameters: the nature of the moving object, the direction of the motion and the rate of the motion. For example, Question 1 concerned a ball being thrown gently in a vertical direction. In half the questions the moving object was a ball and in the other half the moving object was a person; in half the questions the direction of motion was vertical and in the other half it was horizontal; and in half the questions the implied rate of motion was "gentle" while in the other half it was "quick'.

As suggested by Tamir (1990), subjects were asked to choose the best answer, rather than the correct answer. This had the advantage of requiring the students to analyse the relative importance of the options, if they believed that more than one was correct.

The test was validated by three physics lecturers at the University of Newcastle. Its reliability, based on the group described below, was shown to be acceptable (Cronbach's alpha = 0.81). Each of the questions had an acceptable facility index (ranging from .39 to .61), discrimination index (ranging from .19 to .26) and distractor efficiency (ranging from .01 to .18).

Samplinq Procedure

The test was administered to all the Year 10 students (15-16 year olds) who were present in four schools in Canberra: a total of 567 students. One school was co-educational, one was girls-only and two were boys-only schools. One of the boys' schools was streamed and the other was unstreamed. All the students had studied forces at high school although some more recently than others. The students were asked to answer every question on the test. Those who did not answer every question (N =22) were not included in the analysis. This was because the analysis of consistency required the assumption that eight questions had been answered.

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RESULTS AND DISCUSSION

The test items and the percentages choosing each option are presented in the Appendix. In each question, both the correct answer and the "motion-implies-force" distractor attracted more responses than the other two distractors.

Consistency of Responses The subjects were grouped according to how frequently they chose the "motion-implies-force" distractor (see Table 1). Of the 545 students, 19% never chose this distractor, with the remaining 81% choosing it at least once; for the whole sample, the average number of times this distractor was chosen for the eight questions was 3.1. Only 6% (N=34) of the students were totally consistent, choosing this distractor for all eight questions. This last figure is lower than was expected. Halloun and Hestenes (1985), found that 40~ of their students were completely consistent. However, they tested university physics students and it is possible that this explains the difference. Licht and Thijs (1990), investigating another alternative conception, found that pupils in higher grades were more consistent than those in lower grades. The results for the correct responses show a similar pattern. Only 10% of the students were consistently correct, and the average number of correct responses was 3.9.

TABLE 1

PERCENTAGES OF SAMPLE SELECTING "MOTION-IMPLIES-FORCE" DISTRACTOR AND CORRECT ANSWER

Number of times this option was chosen

OPTION 0 1 2 3 4 5 6 7 8

motion-implies-force 19 16 11 14 14 9 5 7 6 distractor % % % % % % % % %

correct answer 13 10 9 14 14 10 8 13 10 % % % % % % % % %

This similarity appears to indicate that the inability of the majority of the students to achieve complete consistency is not just a feature of the alternative conception, but rather it may be rooted in a general inability to apply ideas consistently across different contexts, even when these contexts are closely related, as was the case here. In contrast, McCIoskey (1983) studied alternative conceptions concerning motion and stated that "they are not random, but systematic. They arise from a general, coherent theory of motion that adequately guides action in many circumstances". The results from the present study indicate that this is possibly only true for a small minority of the students.

Effect of Context Table 1 shows that many of the students chose the alternative conception either once or twice. Very little can be said about these two groups because probability suggests that in a test of eight multiple choice questions a person who was using random guessing would be expected to answer about two questions consistently.

However, a large number of people did choose the alternative conception either three, four or five times. It is possible that these people were responding fairly consistently to one of the

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contextual parameters (e.g. "ball" questions) but not the other (e.g. "person" questions). To investigate this possibility the data were examined in the following way.

Individuals who appeared to be consistent in one group of questions but not in the other were identified. The criterion was that the difference between their scores for each group should be at least 3. For example, one student chose the motion-implies-force distractor four times in questions which concerned a ball in motion, but chose the correct response in each of the four questions which concerned a person in motion; and another student chose this distractor in four of the "person" questions but in only one of the "ball" questions.

These results are presented in Table 2, which reveals that some people tended to answer "ball" questions differently from "person" questions (with more people applying the alternative conception to the former). Other people tended to answer questions about vertically-moving objects differently from horizontally-moving objects (with more people applying the alternative conception to the latter). Another group of peopie tended to answer questions about gently- moving objects differently from quickly-moving objects (with equal numbers in both).

TABLE 2 NUMBERS OF PEOPLE WHO CHOSE THE "MOTION-IMPLIES-FORCE" DISTRACTOR

CONSISTENTLY FOR ONE GROUP OF QUESTIONS ONLY.

Context ball person vertical horiz, gentle quick Total 20 3 11 36 5 5

Thus, it appears that some people believed that the type of object was important when considering the causes of the motion. Other studies have obtained similar results. Whitelock (1991) found that the animate nature of moving objects was an important factor to some students; and Fischbein et al. (1989) identified naive subjects whose responses were influenced by the shape, the weight and the function of the moving body.

The results also indicated that the direction of movement may have been an important contextual factor for some people. A relatively large number of people in this group chose the alternative conception when the object was moving horizontally rather than vertically. It is possible that these people were selecting gravity as being the main force operating in vertical movement but that in horizontal movement the main force was the "force in the direction of the motion'. The individual results show some support for this: several students chose the correct response in the four "vertical" questions, but chose the "motion-implies-force" distractor in the four "horizontal" questions.

However, these people whose patterns of responses separated the questions along broad contextual lines represented only a small percentage (15%) of the total group. It is possible that other people were perceiving more subtle differences between contexts. To investigate this, the data were examined in the following way.

The questions were paired according to contexts which they had in common. For example, there were two questions about a ball moving vertically, two about a ball moving horizontally, and two about a person moving vertically. For each pair, the number of people who chose the "motion-implies-force" distractor in both questions was found. The results are shown in Table 3.

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TABLE 3 NUMBERS OF PEOPLE WHO CHOSE THE "MOTION-IMPLIES-FORCE" DISTRACTOR

IN BOTH OF TWO CLOSELY-RELATED QUESTIONS

Context Total Context Total ball horiz. 164 person gentle 89 ball vertical 182 person quick 118 person vertical 111 vertical gentle 95 person horiz. 113 vertical quick 132 ball gentle 131 horiz, gentle 145 ball quick 134 hodz. quick 135

It is apparent that some combinations of questions attracted considerably more responses than others. The questions concerning a ball moving horizontally attracted the greatest number, followed by the questions concerning a ball moving vertically. Thus, there is some evidence that people were responding to an interplay between contexts. For example, one student chose the correct answer in five of the questions, had one incorrect, but chose the "motion-implies-force" distractor in the two questions concerning a ball moving horizontally.

IMPLICATIONS FOR RESEARCH AND TEACHING

Although many students applied the "motion-implies-force" conception in some contexts, very few consistently generalised it to a range of everyday situations. The fact that this also applied to the correct scientific theory points to a general problem which students seem to have in recognising the similarities between contexts. Teaching procedures need to be developed which enhance this skill.

For some people, it is possible to identify certain contexts in which the "motion-implies-force" conception is more likely to be used. These include motion in a horizontal direction, motion of a ball rather than a person, and particularly a combination of these: motion of a ball in a horizontal direction. This information has a potential use in the process of conceptual change. Put very simply, this process requires individuals to recognise that they have an understanding which is not satisfactory, and then to change it by exposure to a range of situations; see Driver (1989) and Saunders (1992). Thus, it is important for the teacher to select contexts which as many students as possible will relate to the alternative conception. The ones identified above could hold promise for this.

The findings of this study need to be corroborated by further research of a more qualitative nature involving techniques such as diagnostic interview. The broad trends identified above should provide fruitful areas for further research in this field.

Acknowledqements

I am grateful to Sid Bourke, Ken Clements, Ross Flanagan, Roy Killen and Jim Miles for their advice and support.

REFERENCES

Driver, R. (1989). Students' conceptions and the learning of science. International Journal of Science Education, 11 (5), 481-490.

Engel Clough, E., & Driver, R.(1986). A study of consistency in the use of students' conceptual frameworks across different task concepts. Science Education, 70 (4), 473-496.

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Finegold, M. & Gorsky, P. (1991). Students' concepts of force as applied to related physical systems: A search for consistency. International Journal of Science Education, 13, 97-113.

Fischbein, E., Stavy, R., & Ma-Naim, H. (1989). The psychological structure of naive impetus conceptions. International Journal of Science Education, 11, 71-81.

Galili, I. & Bar, V. (1992). Motion implies force: where to expect vestiges of the misconception? International Journal of Science Education, 14, 63-81.

Halloun, I. & Hestenes, D. (1985). The initial state of college physics students. American Journal of Physics, 53, 1043-1055.

Licht, P. & Thijs, G. (1990). Method to trace coherence and persistence of preconceptions. International Journal of Science Education, 12, 403-416.

McCIoskey, M. (1983). Intuitive physics. Scientific American, 248, 114-122. Osborne, R.J. & Gilbert, J.K. (1980). A technique for exploring students' views of the world.

Phvsics Education, 15, 376-379. Saunders, W.L. (1992). The constructivist perspective: implications and teaching strategies for

science. School Science and Mathematics, 92, 136-141. Summers, M. & Kruger, C. (1992). Research into English primary school teachers'

understanding of the concept energy. Evaluation and Research in Educatioq, 6, 95-111. Tamir, P. (1990). Justifying the selection of answers in multiple choice items. International

Journal of Science Education, 12, 563-573. Vosniadou, S. & Brewer, W.F. (1989). The concept of the Earth's shape: a study of conceptual

chanqe in childhood. Manuscript (University of Illinois, Illinois). Whitelock, O. (1991). Investigating a model of commonsense thinking about causes of motion

with 7 to 16-year-old pupils. International Journal of Science Education, 13, 321-340.

AUTHOR

DR. DAVID PALMER, Lecturer, Faculty of Education, University of Newcastle, NSW 2308. Specialization: science education.

APPENDIX

The test questions are presented below. The numbers in brackets are the percentage who chose each distractor (N =545).

FORCES IN SPORT Please circle the best answer from the ones given.

1. A person gently throws a ball straight up into the air. When the ball is on the way up (and well clear of the person's hand) the total force on the ball is

A. up (35%) B. zero (10%) C. down (39%) D. none of the above (16%)

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2. At cycle training at an indoor stadium, a person gives a cyclist a push start along a flat, level stretch of the floor to see how far the bike will roll before it stops. The cyclist does not pedal. While the bike is rolling straight forward at some speed (after it has been pushed), the main force affecting the cyclist would be in which of these directions?

A. > (56%) B. < (34%) C. side on to the cyclist (2%) D. no force (8%)

3. A golfer gently hits a golf ball so that it rolls across the flat, level green and falls into the hole. After the ball has been hit, and while it is still rolling slowly forward towards the hole, the motion of the ball would be mainly influenced by

A. a force attracting it to the hole (2%) B. a force acting on the ball in the direction in which it is

moving (50%) C. no forces at all (8%) D. a force acting in the opposite direction to which it is

moving (41%)

4. A gymnast is jumping on a trampoline. On one jump, after the person has left the trampoline and is going upwards rapidly, most of the force on the person would be in which direction?

A. in a downwards direction (55%) B. in an upwards direction (39%) C. in no direction because there would be no force on

the person (4%) D. in the direction in which the person is facing (1%)

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5. A girl on roller skates gently pushes off from a wall and slowly rolls a short distance along a flat, level path. She does not attempt to skate forward, but just rolls until she stops. As she is rolling slowly forward (well away from the wall) she would be mainly influenced by a force

A. from the wall, repelling her (16%) B. pushing her to one side or another (2%) C. acting in the direction she is moving (36%) D. acting in the opposite direction to which she is

moving (46%)

6. In cricket, a batsman misjudges a shot and hits the ball so that it goes straight up high into the air. After the ball was hit and while it was travelling rapidly upwards the main force on the ball would have been

A. acting downwards on the ball (52%) B. no force present at all (3%) C. acting straight upwards on the ball (35%) D. none of the above (9%)

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7. A hockey player hits a ball which rolls very quickly along the flat, level surface of the hockey field. As the ball is moving quickly along (well after it has been hit) it would be mainly affected by a force in a

A. sideways direction (2%) B. backwards direction (42%) C. forwards direction (49%) D. no force present (7%)

8. After winning the grand final, the team lifts the coach up and throws him gently up into the air 3 times to celebrate. On one of these times, after the coach has been thrown and while he is still moving straight upwards, the main force on him would be

A. acting straight upwards (28%) B. acting straight downwards (61%) C. absent, or no force (4%) D. none of the above (,7%)