Directory UMM :Data Elmu:jurnal:A:Advances in Physiology Education:Vol277.Issue6.Dec1999:

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UNDERGRADUATE STUDENTS’ MISCONCEPTIONS

ABOUT RESPIRATORY PHY SIOLOGY

Joel A. Michael,1 _{Daniel Richardson,}2 _{Allen Rovick,}1 _{Harold Modell,}3 _{David Bruce,}4 _{Barbara Horwitz,}5 Margaret Hudson,6 _{Dee Silverthorn,}7 _{Shirley Whitescarver,}8 _{and Steven Williams}9

1_{Depa rtm ent of Molecula r Biophysics a nd Physiology, Rush Medica l College, Chica go, Illinois 60612;} 2_{Depa rtm ent of Biophysics a nd Physiology, University of Kentuck y, Lexington, Kentuck y 40536;}3_{Na tiona l}

Resource for Com puters in Life Science Educa tion, Sea ttle, Wa shington 98115;4_{Depa rtm ent of Biology,} Whea ton College, Whea ton, Illinois 60187;5_{Section of Neurobiology, Physiology, a nd Beha vior, University}

of Ca lifornia , Da vis, Ca lifornia 95616;6_{Depa rtm ent of Biology, Sea ttle University, Sea ttle, Wa shington} 98122;7_{Depa rtm ent of Zoology, University of Texa s, Austin, Texa s 78712;} 8_{Depa rtm ent of Biologica l} Science a nd Nursing, Lexington Com m unity College, Lexington, Kentuck y 40506; a nd 9_{Depa rtm ent of}

Biology, Glenda le Com m unity College, Glenda le, Arizona 85302

A

pproximately 700 undergraduates studying physiology at community colleges, a liberal arts college, and universities were surveyed to determine the prevalence of four misconceptions about respiratory phenomena. A misconception about the changes in breathing frequency and tidal volume (physiological variables whose changes can be directly sensed) that result in increased minute ventilation was found to be present in this population with comparable prevalence (,60%) to that seen in a previous study (9). Three other misconceptions involving phenomena that cannot be experienced directly and therefore were most likely learned in some educational setting were found to be of varying prevalence. Nearly 90% of the students exhibited a misconception about the relationship between arterial oxygen partial pressure and hemoglobin saturation. Sixty-six percent of the students believed that increasing alveolar oxygen partial pressure leads to a decrease in alveolar carbon dioxide partial pressure. Nearly 33% of the population misunderstood the relationship between metabolism and ventilation. The possible origins of these respiratory misconceptions are discussed and suggestions for how to prevent and/or remediate them are proposed.

AM. J. PHYSIOL. 277 (ADV. PHYSIOL. EDUC. 22): S127–S135, 1999. Key words:mental models

When developing a course, instructors work under the assumption that they know the knowledge state of the typical entering student. On the basis of that assumption, they establish the educational objectives, content, and teaching modalities for the course. In-structors may recognize that students come to physiol-ogy with misconceptions because students often ver-balize them in class or answer exam questions in a way that reveals faulty thinking. However, it is more

common for instructors to be unaware that students hold significant misconceptions about the subject matter (5). Moreover, the prevalence of these miscon-ceptions in the incoming student population has seldom been systematically addressed.

Michael (9) showed that a significant misconception about ventilation exists among a large population of undergraduate students. Students were asked to pre-dict the change in tidal volume that would occur

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when an individual is exposed to a common situation in which minute ventilation increases (e.g., exercise). They were told that breathing frequency increases in this situation. Approximately one-half of the nearly 400 students surveyed responded that tidal volume either decreased or remained unchanged. This is not a misconception that faculty would expect to find in this population because both changes in breathing frequency and tidal volume can be directly sensed by the individual; one would expect that reflection on past experience with exercise would lead students to a correct prediction. This misconception, then, is an example of an experientially acquired misconception that is similar, in that regard at least, to many of the misconceptions about motion (5, 6, 8) and other physical phenomena (1, 12).

Misconceptions are also known to arise from experi-ences that students have in the classroom; imprecise use of language by teachers and students (7, 19), imprecisely formulated analogies (3), and the ‘‘car-toon’’ figures found in textbooks (2) can all lead students to build incorrect mental models of scientific phenomena.

The primary purpose of this study was to determine the prevalence of selected misconceptions in respira-tory physiology that, in our judgment, most likely resulted from some classroom experience. A second purpose was to determine the likely causes of the misconceptions found to be present. To achieve this objective, we surveyed a large population of under-graduate students enrolled in a variety of life science courses that included significant components of physi-ology.

METHODS

Respiratory Misconceptions Inventory

At a meeting of the authors, a list of ‘‘common’’ misconceptions about respiratory physiology was compiled. The list was drawn from our previous experiences interacting with students. Eleven ceptions were identified. Statements of these miscon-ceptions are presented in Table 1.

From the list in Table 1, we chose four misconcep-tions to serve as the basis of a respiratory physiology

misconceptions inventory. A misconception was cho-sen for inclusion in the inventory because we thought it was prevalent and of significant consequence for learning in our respective student populations or because it was to be used in assessing the efficacy of laboratories in helping students to remediate miscon-ceptions (H. Modell, J. Michael, T. Adamson, J. Gold-berg, B. Horwitz, D. Bruce, M. Hudson, S. White-scarver, and S. Williams, unpublished observations). The four misconceptions chosen deal with 1) tidal volume (VT) and breathing frequency (f) as determi-nants of minute ventilation, the ‘‘VT/fmisconception’’; 2) the relationship between hemoglobin saturation (Sa) and partial pressure of oxygen in arterial blood (PO2), the ‘‘Sa/PO₂ misconception’’; 3) O2 and CO2 exchange in the lungs, the ‘‘O2/CO2misconception’’; and 4) the relationship between metabolism and ventilation, the ‘‘met/vent misconception.’’

Each item in the inventory has two components. The prediction component describes an experiment or disturbance involving the respiratory system and re-quests the students to predict the change that will occur in some variable as a result of the perturbation (see Table 2). Each prediction (correct or incorrect) then directs the students to a second item that presents possible ‘‘explanations’’ for their prediction.

TABLE 1

Student misconceptions about r espiratory phenomena

1) PIO2is independent of altitude.

2) Atmospheric pressure is increased at high altitude.

3) Increases in minute ventilation are the result of increased breathing frequency (f) but tidal volume (VT) does not change or decrease; referred to as the ‘‘VT/f misconcep-tion.’’

4) The partial pressure of O2in the blood is determined by

hemoglobin saturation; the ‘‘Sa/PO2misconception.’’ 5) PaO2and arterial oxygen content are ‘‘equivalent.’’

6) A change in inspired O2must change alveolar CO2; the

‘‘O2/CO2misconception.’’ 7) The body can ‘‘run out’’ of oxygen.

8) The respiratory system homeostatically regulates ventila-tion.

9) Each breath is the result of a single action potential in the nerve(s) to the respiratory muscle(s).

10) Increases in V˙O2lead to increased ventilation because the

body ‘‘needs’’ more oxygen; the ‘‘met/vent misconcep-tion.’’

11) The lungs are expanded by increased pressure in the alveoli.

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Students are asked to choose the explanation that best fits their prediction (9, 13, 18). The explanations for misconceptions (shown in Tables 5–8) were also drawn from our interactions with students learning respiratory physiology in our courses.

Pr otocol

The respiratory misconceptions inventory was admin-istered during the first week of classes (in some cases on the first day) as part of a larger survey that also gathered demographic data about the students and determined the students’ level of knowledge about topics prerequisite to learning respiratory physiology (15).

Populations Surveyed

Students enrolled in seven different educational institu-tions across the country were surveyed. The schools

included two community colleges, a highly selective small liberal arts college, a small private university, and three state research universities. The student populations were equally diverse. These institutions, the courses involved, and the number of students involved at each site are described in Table 3. Table 4 provides a capsule description of the students respond-ing to the survey.

TABLE 2

Respiratory misconceptions survey questions

VT/f

A classmate is late for the exam and runs up 5 flights of stairs to the exam room. When she arrives you notice that her breathing frequency is increased. At the same time you notice that her depth of breathing (how much air she takes with each breath) is

a) greater than normal

b) less than normal

c) unchanged Sa/PO2

Carbon monoxide (CO) binds to hemoglobin much more strongly than does oxygen. As a result of CO being in the blood, less oxygen is bound to hemoglobin, and the partial pressure of oxygen in the blood is

a) increased

b) decreased

c) unchanged O2/CO2

You begin breathing 100% oxygen through a mask. While you breathe from the mask the amount of carbon dioxide in your lungs

a) increases

b) decreases

c) stays the same Metabolism/ventilation

When the metabolism of the body increases, ventilation will

a) increase

b) decrease

c) remain unchanged

TABLE 3

Under graduate student populations studied

Type of

Institution Course Type

No. of Students LAC Animal physiology (lecture and lab) 26 SU1 Vertebrate physiology (lecture only) 66 Human body (lecture only) 164 SU2 Elementary physiology (lecture only) 32 CC1 Human anatomy and physiology (lecture

and lab)

45 SU3 Systems physiology (lab only) 147 PU Anatomy and physiology (lecture and lab) 48 CC2 Human anatomy and physiology (lecture

and lab)

145 Introduction to human anatomy and

physiology for nonmajors (lecture and lab)

LAC, liberal arts college; SU1–SU3, state research universities 1–3; CC1 and CC2, community colleges 1 and 2; PU, private university.

TABLE 4

Some personal characteristics of the student populations r esponding to questionnair e

Gender

Female 71%

Male 29%

Age, yr

16–19 19%

20–24 61%

25–29 8%

301 12%

Ethnicity

Native American 1%

Asian 22%

Black 3%

Hispanic 7%

White 62%

Other 5%

Years in college

,1 9%

1–2 31%

3–4 39%

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RESULTS

Pr evalence of Misconceptions

The VT/f misconception was present in 56.7% of the population studied. Across the seven institutions, the prevalence at individual schools ranged from a low of 31.1% to a high of 69.4%.

The Sa/PO₂ misconception was much more common,

with 89.9% of the population demonstrating it. The variation across the seven institutions was small, from a low of 82.2% to a high of 100%. This was by far the most common of the four misconceptions surveyed. The O2/CO2 exchange misconception was present in slightly.67.9% of the student population. There was little difference among schools; the prevalence at individual schools ranged from 57.7% to 72.3%. The met-vent misconception was the least common of the misconceptions surveyed; only 32% of the

popula-tion exhibited it, and the range extended from a low of 16.7% to a high of 46.2%.

The prevalence of the four misconceptions at each of the seven institutions is show in Fig. 1 (at two institutions, state research university 1 and commu-nity college 2, students in two different courses were surveyed).

Ex planations of Misconceptions

Tables 5–8 show the explanations that were selected for incorrect predictions (i.e., when a misconception is present). Each table shows the proportion of students exhibiting that misconception who chose those specific explanations. Because of student errors in selecting the follow-up item to be answered, the total number of responses listed is smaller than the total number of students sampled who held the misconception.

FIG. 1.

Pr evalence of each of the four misconceptions among students at each educational institution and in total population studied. CC1 and CC2, community colleges 1 and 2; PU, private university; SU1–SU3, state r esear ch universities 1–3; LAC, liberal arts college.

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DISCUSSION

The frequency of occurrence of the VT/f misconcep-tion (involving a phenomenon that all students will have personally experienced) found in this study is similar to that already seen in a similar population of students, and the reasoning that led the present population to this misconception is also the same (9). Most students erred by predicting that VT would decrease. The majority of these students believe that with increased breathing frequency, there is not enough time for a deeper breath (Table 5, expla na -tion 1). The next most common explanation is that minute ventilation, VT3 f, is held constant (Table 5, expla na tion 2). Other common explanations arise from a faulty understanding of how inspiration is produced ( Table 5,expla na tions 3–6).

The three other misconceptions surveyed are ones that are most likely to have arisen from some experi-ence in a formal or informal educational setting. None of the phenomena considered can be perceived di-rectly without sophisticated instrumentation, and they are not phenomena that are likely to have been encountered outside of an educational setting. The misconception about the relationship between hemoglobin saturation and PO₂ (Sa/PO₂ misconcep-tion) was the most prevalent, and in one course every student exhibited it (see Fig. 1). In the experience of most teachers of respiratory physiology, this is prob-ably the least surprising misconception. Students at all levels have great difficult with the interlocking con-cepts of gas solubility, the partial pressure of a gas in a liquid, and the phenomenon of oxygen binding to hemoglobin. About three times as many students thought that exposure to CO would decrease arterial PO₂ as those who thought that PO₂ would increase. The most common explanation (Table 6,expla na tion 8) for predicting that PO₂ would decrease may arise

from equating hemoglobin O2 saturation, which de-creases because of the binding of CO, with arterial PO2, which therefore must also decrease. The next most common explanation (Table 6, expla na tion 7) appears to arise out of a belief that if the partial pressure of one gas (CO) increases, then the partial pressure of the other gas (O2) must decrease. The most common explanation for the erroneous predic-tion that PO₂ will increase (Table 6, expla na tion 1)

may arise from a mental model in which the blood in the pulmonary capillaries is seen as a closed compart-ment with no connection to the alveolar gas or, ultimately, to the atmosphere.

The O2/CO2 misconception is the second most preva-lent misconception. As many students thought that breathing 100% O2 would increase lung CO2 content as those who thought that CO2 would decrease. The most common explanation for erroneously predicting that CO2would increase (Table 7,expla na tion 1) may arise from the common use of the term ‘‘exchange’’ to describe the ‘‘function’’ of the respiratory system (10). Students may assume that this refers to a process in which each O2 molecule taken up necessarily causes a CO molecule to be lost to the atmosphere. This may, in part, arise from a faulty understanding of TABLE 5

Ex planations for VT/fmisconception

A classmate is late for the exam and runs up 5 flights of stairs to the exam room. When she arrives you notice that her breathing frequency is increased. At the same time you note that her depth of breathing (how much she takes in with each breath) is

a) greater than normal (correct prediction)

b) less than normal

c) unchanged

Frequency* Tidal volumedecrea sedbecause

1) breathing faster doesn’t allow time to

breathe as deeply 214/367

2) the product of breathing frequency times the depth of breathing is held constant by the body

63/367

3) when you breathe faster, you can’t produce

as negative a pressure in your lungs 58/367

4) the body needs to minimize the energy

spent expanding the lungs 32/367 Tidal volume isuncha ngedbecause

5) the depth of breathing is always held

con-stant by the nervous system 5/27

6) depth of breathing is only determined by

the anatomy of the lungs and chest wall 5/27

7) since she is breathing faster there is no

need to breathe more deeply 11/27

8) deeper breaths would dilute the oxygen in

her lungs 6/27

*The total number of explanations is less than the number of misconceptions because of student errors in selecting the follow-up item to be answered.

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the relationship between O2uptake and the metabolic production of CO (Table 7, expla na tions 1 and 3, which are equivalent statements, andexpla na tion 7). It also appears that students believe that increased alveolar PO₂must result in increased O₂uptake (Table

7,expla na tions 1and3). Another contributor to this misconception is a common student mental model of the lungs as a closed system with a fixed volume; if the volume (or pressure) of one gas increases, then the volume (or pressure) of the other gas must decrease (Table 7,expla na tions 5and6).

The relationship between metabolic activity and venti-lation (the met-vent misconception) was the least prevalent misconception, although in one class 46% of the students exhibited it. The most common source of misconceptions here appears to be student belief that there is no connection between metabolism and ventilation (Table 8,expla na tions 5and6). Addition-ally, students seem to lack knowledge about

metabo-lism (Table 8, expla na tions 2–5 and 8) and have misunderstandings about the respiratory controller (Table 8,expla na tions 2,3, and5).

A common source of prediction errors (resulting in the appearance of a misconception) is the belief of many students that essentially all physiological param-eters are homeostatically regulated and thus are held more or less constant. It seems likely that the empha-sis that is placed on homeostaempha-sis as a central organiz-ing principle for physiology is overgeneralized, a common problem when learning about a new domain (3, 16).

The significance of teleological reasoning in shaping students’ thinking about physiology has been noted often (14, 17). Examination of the reasons selected for predictions reveals that many students in the popula-tion studied selected explanapopula-tions that are clearly descriptions of teleology (Table 5,expla na tions 4and TABLE 6

Ex planations for Sa/ PO2misconception

a) increased

b) decreased

c) unchanged (correct prediction)

Frequency* PO₂isincrea sedbecause

1) oxygen is driven from hemoglobin into

blood plasma 70/163

2) the body needs more oxygen in the plasma

to compensate for the presence of CO 48/163

3) respiration is stimulated by the presence of

CO in the blood 25/163

4) the amount of oxygen in the plasma plus the amount of oxygen bound to hemo-globin is held constant

20/163 PO2isdecrea sedbecause

5) CO reduces metabolism and the body thus

needs less oxygen 8/455

6) CO depresses respiration 47/455

7) the partial pressure of the CO reduces the partial pressure of the oxygen since the sum of the two must be a constant

134/455

8) CO displaces oxygen in the blood 266/455 *The total number of explanations is less than the number of misconceptions because of student errors in selecting the follow-up item to be answered.

TABLE 7

Ex planations selected for O2/ CO2ex change misconception

You begin breathing 100% oxygen through a mask. While you breathe from the mask the amount of carbon dioxide in your lungs

a) increases

b) decreases

c) stays the same (correct prediction)

Frequency* Amount of CO2increa sesbecause

1) increased oxygen uptake leads to increased

carbon dioxide production 134/226

2) more space is available in the lungs for

carbon dioxide 5/226

3) with increased oxygen the body produces

more carbon dioxide 65/226

4) increased oxygen depresses respiration causing carbon dioxide to build up in the lungs

22/226 Amount of CO2decrea sesbecause

5) oxygen replaces carbon dioxide in the

lungs 77/243

6) less space is available in the lungs for

carbon dioxide 40/243

7) with increased oxygen the body does not

produce as much carbon dioxide 52/243

8) increased oxygen stimulates respiration

causing carbon dioxide to be blown off 74/243 *The total number of explanations is less than the number of misconceptions because of student errors in selecting the follow-up item to be answered.

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7; Table 6,expla na tion 2; Table 8,expla na tions 3,6, and8); i.e., ‘‘the body needs more oxygen’’ or ‘‘the body needs to get rid of the same amount of carbon dioxide as before.’’ Although such explanations are troubling to teachers of physiology, it is not clear whether the students selecting these choices are, in fact, thinking teleologically or whether they are select-ing the only language they recognize to explain their choices (17).

The relative uniformity with which students at quite different educational institutions (community col-leges, a small liberal arts college, a small private university, and three large research universities) ex-hibit the misconceptions surveyed in this study is worth noting. The student populations we studied varied in ethnicity and age (see Table 4) and in their career goals (unpublished observations). Studies in other domains have revealed similarly widespread misconceptions (20).

Potential Sour ces of Misconceptions

Where do the misconceptions we have detected come from? Without some understanding of their origin it is, of course, difficult to know what to do about them.

Ex perience. It is clear that an individual’s personal experience can give rise to misconceptions. In the domain of physics, it is well established that miscon-ceptions about motion arise from the fact that the real world does not always appear to behave in a way that is described by Newton’s Laws (5, 6, 8). A common perceptual illusion involving the Doppler shift has been shown to give rise to a misconception (12). Furthermore, the faulty mental models about motion that may be present work quite well in the real world. Thus, even when the accepted scientific model is learned in the classroom, an incorrect model (miscon-ception) may continue to be utilized outside of the classroom. Similarly, Michael (9) has demonstrated that misconceptions about changes in ventilation arise from the misperception or the faulty interpretation of physiology responses that are personally experienced. It should be kept in mind, however, that experien-tially based misconceptions may be reinforced by educational experiences of the types described be-low.

Language. Another important source of misconcep-tions is the imprecise use of language by both teachers and students. Veiga et al. (19) have described the consequence of teachers’ imprecise use of language in teaching about heat and temperature; student miscon-ceptions are reinforced by the very language that they hear from their teachers. Jacobs (7) has pointed out that every science discipline uses terms from our everyday (‘‘lay’’) language that also have a special definition within the discipline. These terms can cause great confusion because students think they know what the terms mean when, in fact, they do not. An example of such a problem in the domains of respiratory and cardiovascular physiology is the term ‘‘elasticity.’’ In lay terms, a rubber band is very elastic and a steel beam is not. However, the meaning of the term ‘‘elastic’’ in physics is exactly the opposite. Thus discussions about the elastic recoil of the lungs or chest wall can result in quite incorrect mental models of respiratory mechanics, and attempts to substitute TABLE 8

Ex planations selected for metabolism-ventilation misconception

When the metabolism of the body increases, respiration will

a) increase (correct prediction)

b) decrease

c) remain unchanged

Frequency* Respirationdecrea ses

1) products of metabolism, such as carbon

dioxide, depress respiration 3/46

2) the nerve or hormonal signal that increases

metabolism depresses respiration 13/46

3) the body doesn’t need as much oxygen since anaerobic metabolism can occur in the absence of oxygen

26/46

4) in order for metabolism to increase

respira-tion must decrease 4/46 Respiration isuncha nged

5) there is no mechanistic connection

between metabolism and respiration 71/150

6) an increase in respiration is not needed for

metabolism to increase 42/150

7) metabolism is controlled by hormones but

respiration is controlled by nerves 30/150

8) the body’s need for oxygen is determined

by metabolism not respiration 7/150 *The total number of explanations is less than the number of misconceptions because of student errors in selecting the follow-up item to be answered.

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the term ‘‘compliance’’ for the term ‘‘elasticity’’ may not help to dispel the confusion.

Visual r epr esentations. The visual representations of important phenomena that are used in textbooks and other media such as computer simulations and animations (21) can also be a source of significant student misconceptions. For example, the illustra-tions meant to describe the process of diffusion of solutes in solution always show the various solute molecules as large ‘‘objects’’ that occupy appreciable space and that can clearly interfere with (by colliding) each other’s movement. Several of the faulty mental models that lead to the misconceptions observed in this study seem to arise from a similar mechanism (2). Analogies. Finally, it is important to recognize that the use of analogies, particularly common in science education at all levels (4), can actually result in the creation of student misconceptions (16). In some cases the simplified pictorial representations of scien-tific phenomena referred to above are analogies and thus potential sources of all of the forms of misconcep-tions cataloged by Spiro et al. (16).

What can we, as teachers of physiology, lear n fr om these r esults?First, we need to recognize that in spite of our best efforts, it is likely that something we do or say in the classroom, or include in our written materials, will contribute to students de-veloping a misconception about some important physi-ological phenomenon. We must, therefore, strive for precision and clarity in our words, use pictorial representations that communicate only what we seek to communicate, and use only carefully thought out analogies as we seek to build our students’ understand-ing with increasunderstand-ingly complex models.

Having done that, we must be prepared to detect the misconceptions being used by our students and then assist them in remediating these faulty models. We have proposed the creation of an active learning environment in our classrooms as an approach to accomplishing both of these goals (10). Providing students with opportunities to test their mental mod-els by making predictions and/or solving problems can provide opportunities for the instructor to detect misconceptions, while at the same time allowing the

students to prove to themselves that their models lead to incorrect predictions, the first step in remediating a misconception (19).

This research was supported by National Science Foundation Grant DUE-965782. The opinions expressed are those of the authors and not necessarily those of the Foundation.

Address for reprint requests and other correspondence: J. Michael, Dept. of Physiology, Rush Medical College, 1750 W. Harrison St., Chicago, IL 60612 (E-mail: [email protected]).

Received 26 January 1999; accepted in final form 26 August 1999.

Refer ences

1. Br na, P.Confronting misconceptions in the domain of simple electrical circuits.Instructiona l Sci. 17: 29–55, 1988.

2. Ebenezer, J. V., and G. L. Erickson. Chemistry students’ conceptions of solubility: a phenomenography.Sci. Educ. 80: 181–201, 1996.

3. Feltovich, P. J., R. J. Spir o, and R. L. Coulson.The nature of conceptual understanding in biomedicine: the deep structure of complex ideas and the development of misconceptions. In:

Cognitive Science in Medicine, edited by D. A. Evans and V. L. Patel. Cambridge, MA: MIT Press, 1989, p. 113–172.

4. Glynn, S. M. Explaining science concepts: a teaching-with-analogies model. In: The Psychology of Lea rning Science, edited by S. M. Glynn, R. H. Yeany, and B. K. Britton. Hillsdale, NJ: Erlbaum, 1991, p. 219–240.

5. Halloun, I. A., and D. Hestenes.The initial knowledge state of college physics students.Am . J. Phys.53: 1043–1055, 1985. 6. Halloun, I. A., and D. Hestenes. Common sense concepts

about motion.Am . J. Phys. 53: 1056–1065, 1985.

7. Jacobs, G.Word usage misconceptions among first-year univer-sity physics students.Int. J. Sci. Educ. 11: 395–399, 1989. 8. McCloskey, M.Naive theories of motion. In:Menta l Models,

edited by D. Gentner and A. L. Stevens. Hillsdale, NJ: Erlbaum, 1983, p. 299–324.

9. Michael, J. A. Students’ misconceptions about perceived physiological responses. Am . J. Physiol. 274 (Adv. Physiol. Educ. 19): S90–S98, 1998.

10. Modell, H. I. How can we help students learn respiratory physiology? Am . J. Physiol. 273 (Adv. Physiol. Educ. 18): S68–S74, 1997.

11. Modell, H. I., and J. A. Michael(Editors). Promoting active learning in the life science classroom.Ann. NY Aca d. Sci. 701: 1–151, 1993.

12. Neuhoff, J. G., and M. K. McBeath.Overcoming naive mental models in explaining the Doppler shift: an illusion creates confusion.Am . J. Phys. 65: 618–621, 1997.

13. Odom, A. L., and L. H. Barr ow.Development and application of a two-tier diagnostic test measuring college biology students’ understanding of diffusion and osmosis after a course of instruction.J. Res. Sci. Tea ch.32: 45–61, 1995.

14. Richar dson, D. R. A survey of students’ notions of body function as teleologic or mechanistic.Am . J. Physiol. 258 (Adv. Physiol. Educ. 3): S8–S10, 1990.

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15. Rovick, A. R., J. A. Michael, H. I. Modell, D. S. Bruce, B. Horwitz, T. Adamson, D. R. Richar dson, D. U. Silverthor n, and S. A. Whitescarver.How accurate are our assumptions about our students’ background knowledge?Am . J. Physiol. 276 (Adv. Physiol. Educ. 21): S93–S101, 1999.

16. Spir o, R. J., P. J. Feltovich., R. L. Coulson, and D. K. Anderson.Multiple analogies for complex concepts: antidotes for analogy-induced misconception in advanced knowledge acquisition. In:Sim ila rity a nd Ana logica l Rea soning, edited by S. Vosniadou and A. Ortony. Cambridge, UK: Cambridge Univ. Press, 1989, p. 498–531.

17. Tamir, P., and A. Zohar.Anthropomorphism and teleology in reasoning about biological phenomena.Sci. Educ. 75: 57–67, 1991.

18. Tr eagust, D. F. The development and use of diagnostic instruments to evaluate students’ misconceptions in science. Paper presented at the Annual Meeting of the American Education Research Association, San Francisco, CA, March 1989. 19. Veiga, M., D. Costa Pereira, and R. Maskill.Teachers’ language

and pupils’ ideas in science lessons: can teachers avoid reinforc-ing wrong ideas?Int. J. Sci. Educ. 11: 465–479, 1989.

20. Wandersee, J. H., J. A. Mintzes, and J. D. Novak.Research on alternative conceptions in science. In: Ha ndbook of Re-sea rch on Science Tea ching a nd Lea rning, edited by D. L. Gabel. New York: Macmillan, 1994, p. 131–210.

21. Williamson, V. M., and M. R. Abraham. The effects of computer animation on the particulate mental model of college chemistry students.J. Res. Sci. Tea ch. 32: 521–534, 1995.

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RESULTS

Pr evalence of Misconceptions

The V

/

f

misconception was present in 56.7% of the

population studied. Across the seven institutions, the

prevalence at individual schools ranged from a low of

31.1% to a high of 69.4%.

The Sa/PO

misconception was much more common,

with 89.9% of the population demonstrating it. The

variation across the seven institutions was small, from

a low of 82.2% to a high of 100%. This was by far the

most common of the four misconceptions surveyed.

The O

/CO

exchange misconception was present in

slightly

.

67.9% of the student population. There was

little difference among schools; the prevalence at

individual schools ranged from 57.7% to 72.3%.

The met-vent misconception was the least common of

the misconceptions surveyed; only 32% of the

popula-tion exhibited it, and the range extended from a low

of 16.7% to a high of 46.2%.

The prevalence of the four misconceptions at each of

the seven institutions is show in Fig. 1 (at two

institutions, state research university 1 and

commu-nity college 2, students in two different courses were

surveyed).

Ex planations of Misconceptions

Tables 5–8 show the explanations that were selected

for incorrect predictions (i.e., when a misconception

is present). Each table shows the proportion of

students exhibiting that misconception who chose

those specific explanations. Because of student errors

in selecting the follow-up item to be answered, the

total number of responses listed is smaller than the

total number of students sampled who held the

misconception.

FIG. 1.

(2)

DISCUSSION

The frequency of occurrence of the VT/

f

misconcep-tion (involving a phenomenon that all students will

have personally experienced) found in this study is

similar to that already seen in a similar population of

students, and the reasoning that led the present

population to this misconception is also the same (9).

Most students erred by predicting that VT

would

decrease. The majority of these students believe that

with increased breathing frequency, there is not

enough time for a deeper breath (Table 5,

expla na

-tion 1). The next most common explana-tion is that

minute ventilation, VT

3 f, is held constant (Table 5,

expla na tion 2). Other common explanations arise

from a faulty understanding of how inspiration is

produced ( Table 5,

expla na tions 3–6).

The three other misconceptions surveyed are ones

that are most likely to have arisen from some

experi-ence in a formal or informal educational setting. None

of the phenomena considered can be perceived

di-rectly without sophisticated instrumentation, and they

are not phenomena that are likely to have been

encountered outside of an educational setting.

The misconception about the relationship between

hemoglobin saturation and P

O₂

(Sa/P

O₂

misconcep-tion) was the most prevalent, and in one course every

student exhibited it (see Fig. 1). In the experience of

most teachers of respiratory physiology, this is

prob-ably the least surprising misconception. Students at all

levels have great difficult with the interlocking

con-cepts of gas solubility, the partial pressure of a gas in a

liquid, and the phenomenon of oxygen binding to

hemoglobin. About three times as many students

thought that exposure to CO would decrease arterial

P

O₂

as those who thought that P

O₂

would increase.

The most common explanation (Table 6,

expla na tion

8 ) for predicting that PO

would decrease may arise

from equating hemoglobin O

saturation, which

de-creases because of the binding of CO, with arterial

P

O₂

, which therefore must also decrease. The next

most common explanation (Table 6,

expla na tion 7)

appears to arise out of a belief that if the partial

pressure of one gas (CO) increases, then the partial

pressure of the other gas (O

) must decrease. The

most common explanation for the erroneous

predic-tion that PO

will increase (Table 6,

expla na tion 1)

may arise from a mental model in which the blood in

the pulmonary capillaries is seen as a closed

compart-ment with no connection to the alveolar gas or,

ultimately, to the atmosphere.

The O

/CO

misconception is the second most

preva-lent misconception. As many students thought that

breathing 100% O

would increase lung CO

content

as those who thought that CO

would decrease. The

most common explanation for erroneously predicting

that CO

would increase (Table 7,

expla na tion 1) may

arise from the common use of the term ‘‘exchange’’ to

describe the ‘‘function’’ of the respiratory system

(10). Students may assume that this refers to a process

in which each O

molecule taken up necessarily

causes a CO molecule to be lost to the atmosphere.

This may, in part, arise from a faulty understanding of

TABLE 5

Ex planations for VT/fmisconception

a) greater than normal (correct prediction)

b) less than normal

c) unchanged

Frequency* Tidal volumedecrea sedbecause

1) breathing faster doesn’t allow time to

breathe as deeply 214/367

2) the product of breathing frequency times the depth of breathing is held constant by the body

63/367

3) when you breathe faster, you can’t produce

as negative a pressure in your lungs 58/367

4) the body needs to minimize the energy

spent expanding the lungs 32/367 Tidal volume isuncha ngedbecause

5) the depth of breathing is always held

con-stant by the nervous system 5/27

6) depth of breathing is only determined by

the anatomy of the lungs and chest wall 5/27

7) since she is breathing faster there is no

need to breathe more deeply 11/27

8) deeper breaths would dilute the oxygen in

her lungs 6/27

*The total number of explanations is less than the number of misconceptions because of student errors in selecting the follow-up item to be answered.

(3)

the relationship between O

uptake and the metabolic

production of CO (Table 7,

expla na tions 1

and

3,

which are equivalent statements, and

expla na tion 7).

It also appears that students believe that increased

alveolar PO

must result in increased O

uptake (Table

7,

expla na tions 1

and

3). Another contributor to this

misconception is a common student mental model of

the lungs as a closed system with a fixed volume; if the

volume (or pressure) of one gas increases, then the

volume (or pressure) of the other gas must decrease

(Table 7,

expla na tions 5

and

6).

The relationship between metabolic activity and

venti-lation (the met-vent misconception) was the least

prevalent misconception, although in one class 46% of

the students exhibited it. The most common source of

misconceptions here appears to be student belief that

there is no connection between metabolism and

ventilation (Table 8,

expla na tions 5

and

6 ).

Addition-ally, students seem to lack knowledge about

metabo-lism (Table 8,

expla na tions 2–5

and

8) and have

misunderstandings about the respiratory controller

(Table 8,

expla na tions 2,

3 , and

5).

A common source of prediction errors (resulting in

the appearance of a misconception) is the belief of

many students that essentially all physiological

param-eters are homeostatically regulated and thus are held

more or less constant. It seems likely that the

empha-sis that is placed on homeostaempha-sis as a central

organiz-ing principle for physiology is overgeneralized, a

common problem when learning about a new domain

(3, 16).

The significance of teleological reasoning in shaping

students’ thinking about physiology has been noted

often (14, 17). Examination of the reasons selected for

predictions reveals that many students in the

popula-tion studied selected explanapopula-tions that are clearly

descriptions of teleology (Table 5,

expla na tions 4

and

TABLE 6

Ex planations for Sa/ PO2misconception

a) increased

b) decreased

c) unchanged (correct prediction)

Frequency* PO2isincrea sedbecause

1) oxygen is driven from hemoglobin into

blood plasma 70/163

2) the body needs more oxygen in the plasma

to compensate for the presence of CO 48/163

3) respiration is stimulated by the presence of

CO in the blood 25/163

4) the amount of oxygen in the plasma plus the amount of oxygen bound to hemo-globin is held constant

20/163 PO2isdecrea sedbecause

5) CO reduces metabolism and the body thus

needs less oxygen 8/455

6) CO depresses respiration 47/455

7) the partial pressure of the CO reduces the partial pressure of the oxygen since the sum of the two must be a constant

134/455

8) CO displaces oxygen in the blood 266/455 *The total number of explanations is less than the number of misconceptions because of student errors in selecting the follow-up item to be answered.

TABLE 7

Ex planations selected for O2/ CO2ex change misconception

You begin breathing 100% oxygen through a mask. While you breathe from the mask the amount of carbon dioxide in your lungs

a) increases

b) decreases

c) stays the same (correct prediction)

Frequency* Amount of CO2increa sesbecause

1) increased oxygen uptake leads to increased

carbon dioxide production 134/226

2) more space is available in the lungs for

carbon dioxide 5/226

3) with increased oxygen the body produces

more carbon dioxide 65/226

4) increased oxygen depresses respiration causing carbon dioxide to build up in the lungs

22/226 Amount of CO2decrea sesbecause

5) oxygen replaces carbon dioxide in the

lungs 77/243

6) less space is available in the lungs for

carbon dioxide 40/243

7) with increased oxygen the body does not

produce as much carbon dioxide 52/243

8) increased oxygen stimulates respiration

causing carbon dioxide to be blown off 74/243 *The total number of explanations is less than the number of misconceptions because of student errors in selecting the follow-up item to be answered.

(4)

7; Table 6,

expla na tion 2; Table 8,

expla na tions 3,

6,

and

8 ); i.e., ‘‘the body needs more oxygen’’ or ‘‘the

body needs to get rid of the same amount of carbon

dioxide as before.’’ Although such explanations are

troubling to teachers of physiology, it is not clear

whether the students selecting these choices are, in

fact, thinking teleologically or whether they are

select-ing the only language they recognize to explain their

choices (17).

The relative uniformity with which students at quite

different educational institutions (community

col-leges, a small liberal arts college, a small private

university, and three large research universities)

ex-hibit the misconceptions surveyed in this study is

worth noting. The student populations we studied

varied in ethnicity and age (see Table 4) and in their

career goals (unpublished observations). Studies in

other domains have revealed similarly widespread

misconceptions (20).

Potential Sour ces of Misconceptions

Where do the misconceptions we have detected come

from? Without some understanding of their origin it is,

of course, difficult to know what to do about them.

Ex perience.

It is clear that an individual’s personal

experience can give rise to misconceptions. In the

domain of physics, it is well established that

miscon-ceptions about motion arise from the fact that the real

world does not always appear to behave in a way that

is described by Newton’s Laws (5, 6, 8). A common

perceptual illusion involving the Doppler shift has

been shown to give rise to a misconception (12).

Furthermore, the faulty mental models about motion

that may be present work quite well in the real world.

Thus, even when the accepted scientific model is

learned in the classroom, an incorrect model

(miscon-ception) may continue to be utilized outside of the

classroom. Similarly, Michael (9) has demonstrated

that misconceptions about changes in ventilation arise

from the misperception or the faulty interpretation of

physiology responses that are personally experienced.

It should be kept in mind, however, that

experien-tially based misconceptions may be reinforced by

educational experiences of the types described

be-low.

Language.

Another important source of

misconcep-tions is the imprecise use of language by both teachers

and students. Veiga et al. (19) have described the

consequence of teachers’ imprecise use of language in

teaching about heat and temperature; student

miscon-ceptions are reinforced by the very language that they

hear from their teachers. Jacobs (7) has pointed out

that every science discipline uses terms from our

everyday (‘‘lay’’) language that also have a special

definition within the discipline. These terms can

cause great confusion because students think they

know what the terms mean when, in fact, they do not.

An example of such a problem in the domains of

respiratory and cardiovascular physiology is the term

‘‘elasticity.’’ In lay terms, a rubber band is very elastic

and a steel beam is not. However, the meaning of the

term ‘‘elastic’’ in physics is exactly the opposite. Thus

discussions about the elastic recoil of the lungs or

chest wall can result in quite incorrect mental models

of respiratory mechanics, and attempts to substitute

TABLE 8

Ex planations selected for metabolism-ventilation misconception

When the metabolism of the body increases, respiration will

a) increase (correct prediction)

b) decrease

c) remain unchanged

Frequency* Respirationdecrea ses

1) products of metabolism, such as carbon

dioxide, depress respiration 3/46

2) the nerve or hormonal signal that increases

metabolism depresses respiration 13/46

3) the body doesn’t need as much oxygen since anaerobic metabolism can occur in the absence of oxygen

26/46

4) in order for metabolism to increase

respira-tion must decrease 4/46 Respiration isuncha nged

5) there is no mechanistic connection

between metabolism and respiration 71/150

6) an increase in respiration is not needed for

metabolism to increase 42/150

7) metabolism is controlled by hormones but

respiration is controlled by nerves 30/150

8) the body’s need for oxygen is determined

by metabolism not respiration 7/150 *The total number of explanations is less than the number of misconceptions because of student errors in selecting the follow-up item to be answered.

(5)

the term ‘‘compliance’’ for the term ‘‘elasticity’’ may

not help to dispel the confusion.

Visual r epr esentations.

The visual representations

of important phenomena that are used in textbooks

and other media such as computer simulations and

animations (21) can also be a source of significant

student misconceptions. For example, the

illustra-tions meant to describe the process of diffusion of

solutes in solution always show the various solute

molecules as large ‘‘objects’’ that occupy appreciable

space and that can clearly interfere with (by colliding)

each other’s movement. Several of the faulty mental

models that lead to the misconceptions observed in

this study seem to arise from a similar mechanism (2).

Analogies.

Finally, it is important to recognize that

the use of analogies, particularly common in science

education at all levels (4), can actually result in the

creation of student misconceptions (16). In some

cases the simplified pictorial representations of

scien-tific phenomena referred to above are analogies and

thus potential sources of all of the forms of

misconcep-tions cataloged by Spiro et al. (16).

What can we, as teachers of physiology, lear n

fr om these r esults?

First, we need to recognize that

in spite of our best efforts, it is likely that something

we do or say in the classroom, or include in our

written materials, will contribute to students

de-veloping a misconception about some important

physi-ological phenomenon. We must, therefore, strive for

precision and clarity in our words, use pictorial

representations that communicate only what we seek

to communicate, and use only carefully thought out

analogies as we seek to build our students’

understand-ing with increasunderstand-ingly complex models.

Having done that, we must be prepared to detect the

misconceptions being used by our students and then

assist them in remediating these faulty models. We

have proposed the creation of an active learning

environment in our classrooms as an approach to

accomplishing both of these goals (10). Providing

students with opportunities to test their mental

mod-els by making predictions and/or solving problems

can provide opportunities for the instructor to detect

misconceptions, while at the same time allowing the

students to prove to themselves that their models lead

to incorrect predictions, the first step in remediating a

misconception (19).

This research was supported by National Science Foundation Grant DUE-965782. The opinions expressed are those of the authors and not necessarily those of the Foundation.

Address for reprint requests and other correspondence: J. Michael, Dept. of Physiology, Rush Medical College, 1750 W. Harrison St., Chicago, IL 60612 (E-mail: [email protected]).

Received 26 January 1999; accepted in final form 26 August 1999.

Refer ences

1. Br na, P.Confronting misconceptions in the domain of simple electrical circuits.Instructiona l Sci. 17: 29–55, 1988.

2. Ebenezer, J. V., and G. L. Erickson. Chemistry students’ conceptions of solubility: a phenomenography.Sci. Educ. 80: 181–201, 1996.

3. Feltovich, P. J., R. J. Spir o, and R. L. Coulson.The nature of conceptual understanding in biomedicine: the deep structure of complex ideas and the development of misconceptions. In:

Cognitive Science in Medicine, edited by D. A. Evans and V. L. Patel. Cambridge, MA: MIT Press, 1989, p. 113–172.

5. Halloun, I. A., and D. Hestenes.The initial knowledge state of college physics students.Am . J. Phys.53: 1043–1055, 1985. 6. Halloun, I. A., and D. Hestenes. Common sense concepts

about motion.Am . J. Phys. 53: 1056–1065, 1985.

7. Jacobs, G.Word usage misconceptions among first-year univer-sity physics students.Int. J. Sci. Educ. 11: 395–399, 1989. 8. McCloskey, M.Naive theories of motion. In:Menta l Models,

edited by D. Gentner and A. L. Stevens. Hillsdale, NJ: Erlbaum, 1983, p. 299–324.

9. Michael, J. A. Students’ misconceptions about perceived physiological responses. Am . J. Physiol. 274 (Adv. Physiol. Educ. 19): S90–S98, 1998.

10. Modell, H. I. How can we help students learn respiratory physiology? Am . J. Physiol. 273 (Adv. Physiol. Educ. 18): S68–S74, 1997.

11. Modell, H. I., and J. A. Michael(Editors). Promoting active learning in the life science classroom.Ann. NY Aca d. Sci. 701: 1–151, 1993.

12. Neuhoff, J. G., and M. K. McBeath.Overcoming naive mental models in explaining the Doppler shift: an illusion creates confusion.Am . J. Phys. 65: 618–621, 1997.

14. Richar dson, D. R. A survey of students’ notions of body function as teleologic or mechanistic.Am . J. Physiol. 258 (Adv. Physiol. Educ. 3): S8–S10, 1990.

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17. Tamir, P., and A. Zohar.Anthropomorphism and teleology in reasoning about biological phenomena.Sci. Educ. 75: 57–67, 1991.

and pupils’ ideas in science lessons: can teachers avoid reinforc-ing wrong ideas?Int. J. Sci. Educ. 11: 465–479, 1989.

21. Williamson, V. M., and M. R. Abraham. The effects of computer animation on the particulate mental model of college chemistry students.J. Res. Sci. Tea ch. 32: 521–534, 1995.