Medical Education 1993, 27, 422-432

Foundations of problem-based learning: some

H. G. SCHMIDT
Department @Educational Development and Research, University of Limburg, Maastricht

Summary. The present article elaborates on chological theorizing on learning and instruc-
cognitive effects of problem-based learning put tion. Since the past century, when psychology
forward by Schmidt, De Volder, De Grave, broke free from contemplative philosophy and
Moust & Patel (1989) and Norman & Schmidt became an empirical science, this synchronicity
(1992). Its purpose is to discuss, in some detail, could be observed time and again. Ifthe issue was
the theoretical premises of this approach to to explain how people obtain knowledge about
learning and instruction. It is argued that prob- their surrounding world, psychology has always
lem-based learning, above all, promotes the moved to and fro between the two poles of
activation of prior knowledge and its elabo- empiricism and rationalism, just like philosophy
ration. Evidence is reviewed demonstrating that of science. It may be useful to pay some attention
these processes actually occur in small-group to these two main trends in the philosophical
tutorials and that the processing of new informa- discussion on the question ofhow people are able
tion is indeed facilitated by discussion of a to know their world. Empiricism, advocated by
relevant problem. These effects must be attri- the British philosophers Bacon, Locke and
buted to a reorganization taking place in the Hume, considers people to be empty slates
knowledge structures of students as a result of (‘tabulae rasae’) on which nature writes down its
problem-oriented study. In addition, a cognitive laws. Scientists are expected to observe carefully
process called epistemic curiosity (or intrinsic and collect systematically data on reality, so that
interest) is enabled. Some directions for further nature will eventually unveil its secrets. So,
research are outlined. The contribution starts, knowledge acquisition is in fact inductive; the
however, with a discussion of the philosophical repetition of events and the regularity with
and pedagogical roots of problem-based which phenomena appear, are, as it were,
learning. imposed on the careful observer as general laws
of which the discovery is the goal of science.
Key words: *education, medical, undergraduate; Contrary to this, rationalism presupposes that
teaching/*methods; problem solving; learning; our knowledge of the world is primarily the
cognition product ofour thinking activity. O n the basis ofa
limited number of assumptions regarding
reality, a theory can be developed to explain that
Introduction
reality by means of deduction. In this notion,
In the course of history, there has been a remark- theories are not so much systematic descriptions
able concurrence between the views of philoso- of reality derived from careful observations, but
phers of science on the nature of the knowledge cognitive structures resulting from -in particu-
acquisition process within the sciences, and psy- lar: logical - reasoning (Popper 1959).
Conceptions with regard to learning and
Correspondence: Professor H. G. Schmidt, Depart-
ment of Educational Development and Research, Uni-
instruction that have emerged rapidly through
versity of Limburg, PO Box 616, 6200 M D the impetus of Thorndike and Watson at the
Maastricht, The Netherlands. beginning of this century all carried the mark of
422
 Foundations of problem-based learning 423

behaviourism, an American branch of empiri- rize such text almost effortlessly. Researchers
cism. However, at the fringe of this dominant and theoreticians within the rationalist tradition
tradition, stressing the influence of the environ- account for this phenomenon by assuming that
ment in shaping the behaviours oflearners, there people engage their prior knowledge of the
has always been a school of thought, influenced subject in the act of comprehension of the text.
by Kant and Descartes, believing that learning Therefore, the amount of prior knowledge avail-
was mainly the result of a person’s cognitive able determines to what extent something new
activity. Dewey (1929) has been a proponent of can be learned. Those who lack relevant prior
this point of view. In his view, knowledge knowledge find it more difficult to understand
cannot actually be ‘transferred’ but the learner and remember new information, because they
has actively to ‘master’ it. The reason for this is have fewer ‘tools’ to construct a meaningful
that already available cognitive structures to be representation of what the text conveys.
found in learners have to be engaged in the task of Although some of these ideas have been
understanding new information and limit the thoroughly articulated in contributions by the
extent to which they can understand new French epistemologist Jean Piaget (1954) and by
information. (The term ‘cognitive structure’ Jerome Bruner (1959), it is striking to see that
refers to knowledge stored in long-term they only became part of mainstream psycho-
memory. This knowledge is considered logical theorizing after the pendulum within the
organized in a certain way; hence cognitive philosophy of science once again swung from
structure.) It is perhaps useful to give an empiricism to rationalism at the beginning of the
example. Most readers have difficulty remem- 1960s. From this perspective, Piaget and Bruner
bering a text such as the following, even if they could be considered early heralds of the so-called
spend considerable time studying it: ‘cognitive revolution’ in psychology.
Problem-based learning (PBL) as a method of
‘Nobody tells productions when to act; they wait instruction stands firm within the rationalist
until conditions are ripe and then activate themselves.
By contrast, chefs in the other kitchens merely tradition and, hence, is strongly influenced by
follow orders. Turing units are nominated by their cognitive psychology (Norman & Schmidt
predecessors, von Neumann operations are all pre- 1992). Its roots can be traced in Dewey’s (1929)
scheduled, and LISP functions are invoked by other plea for the fostering of independent learning in
functions. Production system teamwork is more children and in Bruner’s (1959, 1971) notion of
laissez-faire: each production acts on its own, when
and where its private conditions are satisfied. There intrinsic motivation as an internal force that
is no central control, and individual productions drives people to know more about their world.
never directly interact. All communication and In addition, the emphasis on active construction
influence is via patterns in the common workspace of theories about the world by students and on
- like anonymous “to whom it may concern”
notices on a public bulletin board.’ (Haugeland 1985) testing their hypothesized consequences deduc-
tively through literature review and discussion
It is, ofcourse, possible to learn this text by heart, definitely has a rationalistic flavour. The role of
provided that enough time is available for repe- problems as a starting point for learning can
tition. The result of such activity, however, will again be attributed to Dewey, who stressed the
probably not be what is usually considered real importance of learning in response to, and in
learning. An important component of actual interaction with, real-life events. In this article,
learning is that the topic studied is understood. the relationship between PBL and cognitive
With the above text, this is difficult, because the psychology, the current guise of rationalism,
issue constantly seems to escape the reader’s will be elaborated upon. The paper presents six
understanding. N o t all readers will have diffi- fundamental principles of learning derived from
culty with understanding this text, though. the science of mind and discuss to what extent
People with a reasonably thorough knowledge of problem-based learning facilitates learning in
the computer sciences, and especially of artificial accordance with these principles. Subsequently,
intelligence, will immediately have understood a number of empirical studies will be discussed;
the text as an attempt to characterize various studies conducted to clarify the nature of the
programming styles, and will be able to memo- learning process underlying PBL. Finally some
424 H. G. Schmidt

items on the agenda for future research in this children can enjoy it. Once successful, compli-
area will be outlined. cations are minimal. Birds seldom get too close.
Rain, however, soaks very fast. Too many people
doing the same thing can also cause problems. One
needs lots of room. If there are no complications, it
Principles of cognitive learning can be very peaceful. A rock will serve as an anchor.
In the course of time, theoreticians and resear- If things break loose from it, however, you will not
get a second chance.’
chers have proposed a variety of learning prin-
ciples (cf. HiIgard & Bower 1975). Recent Subjects who studied texts such as this with an
developments suggest that those principles can accompanying title (e.g. ‘Making and flying a
be reduced to a relatively small set of theorems kite’) remembered almost twice as much
summarizing the state of the art in the area of information as those who studied that same text
learning. This small set of principles will be without a title. Bransford & Johnson (1972)
exemplified below. accounted for this phenomenon by assuming that
both groups had cognitive structures available
( 1 ) The prior knowledge people have regarding a with respect to what is involved in flying kites,
subject is the most important determinant of the but that this knowledge is not activated by the
nature and amount of new information that can be text itself. The title does activate this knowledge,
thereby creating a context through which new
processed
information could be related to existing know-
This principle has already been exemplified ledge, resulting in superior memory. The
through the computer science excerpt taken from example given may seem quite exceptional. In
Haugeland (1985). One of its implications is that regular educational contexts, however, many
the better students, those who have sufficient examples are documented in which learners do
prior knowledge to profit from instruction, will not seem able to relate new information to what
learn more than those who have not, making the they already know about a certain subject. Much
gap between the two groups wider as instruction research has been conducted especially with
proceeds. Another implication is that difficulty regard to science education (Caramazza et a / .
level of learning materials such as books or 1981; Champagne et al. 1983).
lectures cannot simply be understood as a func-
tion of the WQ in which the material is pre-
sented, but also has to do with the knowledge (3) Knowledge is structured. The way in which it is
structured in memory makes it more or less accessible
level of the audience for which the material is
intended. The importance of prior knowledge for use
level for instruction has been stressed again and How do psychologists imagine the knowledge
again by educational psychologists, beginning structures responsible for much of human per-
with Ausubel in 1960, but has been largely formance? Here is a definition: Knowledge conrists
ignored by educators (e.g. Ausubel 1968). of propositions that are structured in semantic nef-
workr. A proposition is a statement that contains
(2) The availability ofrelevant prior knowledge is a two concepts and their interrelation. The follow-
necessary, yet not sufficient, condition for ing are examples of propositions within the field
of medicine:
understanding and remembering new information.
Prior knowledge also needs to be activated by cues in (1) Bacteria produce toxines
the context ofwhich the information is being studied
Bransford &Johnson (1972) presented experi- (produce)
mental subjects with texts such as the following
with the instruction to learn them by heart: (2) Antibodies render toxines harmless
‘A newspaper is better than a magazine. A seashore is
frenderl
a better place than the street. At first, it is better to
run than to walk. You may have to try several times.
It takes some skill but it’s easy to learn. Even young
 Foundations of problem-based learning 425

vasoa ciive
is activated

s e w shock

Figure 1. Part of a semantic network based on an explanation protocol produced by a fourth-year medical student.
Links between concepts can be causal (cau), conditional (cond), temporal (temp), attributional (att) or locational
(loc). In addition, they can indicate that the second node is a specification of the first (spec). Other qualifiers are:
negative (neg), identity (iden) and class relation (isa). (Adapted from Schmidt & Boshuizen 1993.)

The special notation derived from Pate1 & therefore not be confused with book knowledge
Groen (1986) makes it easy to display knowledge as such. It is, in fact, a reflection of a person's
as networks o f concepts and their interrelations. experiences, views and ideas. Figure 1shows part
Thus, semantic networks consist o f large of a semantic network produced by a fourth-year
numbers ofpropositions such as these, relating to medical student while trying t o make sense out o f
each other in a web-like fashion. They are a clinical case o f a young drug addict w h o may
entirely idiosyncratic, that is no t w o subjects have been bitten by a cat and develops a septic
have exactly the same knowledge about a certain shock.
topic. Semantic networks impose structure upon The amount of detail of such a knowledge
reality which otherwise would be perceived as an structure, the number of relations between con-
undifferentiated mass. These structures d o not cepts and the way in which it is organized, will
necessarily represent reality accurately; in fact influence what can be done with that knowledge.
gross departures from reality are often observed O n e o f the reasons, for instance, that students
in students. What is important t o note is that they seem to be unable actually to use in a clinical
provide the means to understand the world. The setting what they have learned previously
depth and accuracy of comprehension is a func- through books and lecturers is that their know-
tion of the quality o f these structures. Know- ledge is not yet organized in a way suitable for the
ledge structured in semantic networks should kind of tasks required ofthem in that setting. It is
426 H . G. Schmidt

generally assumed that the necessary restructur- (5) The ability to activate knowledge in the long-
ing of the knowledge base only takes place in term memory and to make it available for use
response to the demands of the tasks posed. depends on contextual cues
This principle, too, can perhaps best be
explained by means of an illustrative study.
( 4 ) Storing information into memory and retrieving Godden & Baddeley (1975) instructed pro-
it can be greatly improved when, during learning, fessional divers to learn lists of words in a paired
elaboration on the material takes place associate task, similar to Anderson’s & Reder’s
Anderson & Reder (1979) were the first to (1979). Half of this group learned the list under
demonstrate the elaboration principle in an water in a pool, whereas the other half worked
experiment. In this experiment, they used a near the pool. Subsequently, half of the subjects
classical psychological research paradigm, the studying under water were taken o u t of the pool
paired-associate task. This task resembles learn- and half of those near the pool were placed into
ing word pairs in foreign language instruction. the water. Finally, all subjects were requested to
The second word of the pair, however, is not the recall as many paired words as possible. The
foreign language associate but a word in the same results clearly showed that those subjects who
language. The task of the leatner in paired-asso- performed the memory task in the same environ-
ciate experiments, thus, is to learn the association ment as in which they had learned the word list
between the two - unrelated - words in the performed considerably better than those who
same language. The following are a few had to retrieve the information in an environ-
examples: ment other than the one in which they had
learned the list. This experiment shows that
dog bike information intentionally learned and incidental
bird school information about context are simultaneously
chair flower stored in a person’s memory (even if the context
man house
is absolutely irrelevant to the learning task, as in
Thc task is that the experimental subjects are to the pool case). Availability ofthe same context at
learn these pairs and in such a way that when the a future point in time facilitates retrieval of the
experimenter presents the first word, ‘dog’, the information. This phenomenon is called the
subjects recall ‘bike’. Anderson & Reder contextual dependency of learning. It can be
instructed half of the group to learn a list similar observed in many situations; from failing to find
to the above example (but of course much the right answers in an examination room
longer). The other half was to do the same yet although the subject matter had been carefully
was instructed to establish actively a relationship studied at home, to finding out that one has to
between the two elements of a pair. For instance, review much of medicine simply because the
in learning the pair ‘dog-bike’ it was suggested appropriate knowledge is not activated while
that the subjects imagine a dog on a bike. seeing patients (as happens to many medical
Subjects instructed to follow this learning students when entering the clerkships).
strategy performed considerably better on a
recall test than the control group. Anderson &
(6) To be motivated to learn, prolongs the amount of
Reder call this active way of dealing with learn-
study time (or processing time, to put it in cognitive
ing material ‘elaboration’, because the learner
psychology terms) and, hence, improves achievement
expands on the relation between two concepts.
According to these investigators, this approach is Someone who feels the urge to learn will in
so successful because elaboration of the resulting general be prepared to spend more time on
network of propositions creates multiple redun- learning than someone who feels less inclined.
dant retrieval paths. This facilitates the rctrieval Hence, a relation between the time spent on
of a concept from memory; the availability of processing subject matter and achievement may
more than one path enhances the probability that be expected. In the literature, a distinction is
a concept will be retrieved. made between two types of drive, or motivation:
 Foundations of problem-based learning 427

intrinsic and extrinsic motivation. Intrinsic (see Spaulding 1991), were influenced by the
motivation is generally considered a kind of case-study method as developed at Harvard Law
curiosity that drives the subject into knowing School in the 1920s (Fraser 1931). In particular
more about a topic. Therefore, it is sometimes the use of cases as an instrument for learning was
called ‘epistemiccuriosity’ or intrinsic interest. It considered appealing (personal communication,
is assumed that this drive is entirely internally Dr Vic Neufeld). Howard Barrows, a neurolo-
propelled without external rewards. Extrinsic gist who arrived at McMaster at the end of the
motivation, on the other hand, is characterized 1960sbecame a major proponent ofthe approach
by the fact that subject matter is studied, not as a (Barrows 1984; Barrows & Tamblyn 1980).
goal in itself, but to achieve other objectives, Problem-based learning is an approach to
such as passing an examination, obtaining a learning and instruction in which students tackle
degree certificate, increasing self-confidence, or problems in small groups under the supervision
having a well-paid job. Here, knowledge acqui- ofa tutor. In most ofthe cases, a problem consists
sition has a means-end function. In the present of a description of a set of phenomena or events
paper we are only interested in the role of that can be perceived in reality. These phe-
epistemic curiosity in learning new information. nomena have to be analysed or explained by the
A study conducted by Johnson & Johnson tutorial group in terms of underlying principles,
(1979) clearly illustrates the effects of epistemic mechanisms or processes. The tools used in order
curiosity. They instructed small groups of child- to do that are discussion of the problem and
ren to study texts that either described the studying relevant resources. An instance is the
economic necessity of surface coal-stripping, or following problem:
rejected surface coal-stripping because of the
I
damage done to the environment. Children that Teafor two
had studied one of these texts were subsequently On a nice day in the summer Henry (5 years old)
returns from school and would like to have a cup oftea.
required to try to convince others who had The tea is soon made and poured, but by accident
studied the other text in a small-group discuss- Henry gets the hot tea over his bare leg. Although his
ion. Compared with a group of subjects that had mother immediately holds the screaming Henry under
studied the texts individually, those who had a gentle jet of cold running water, his leg looks badly
affected; he has burst blisters and the entire anterior side
discussed the controversial issue spent more time of his thigh is quite red. The doctor takes care of the
studying additional information and watched a wound and asks Henry to come to surgery the next
documentary about the topic more often. day. Because the wound is patchy and locally covered
According to Johnson & Johnson, they had with a whitish coating, Henry is then referred to the
become intrinsically interested in the subject due hospital. Despite optimal care, part of the wound
(approx. 10 X 1Ocm) has still not healed completely
to the controversy discussion. This experiment after three weeks.
and others (e.g. Lowry &Johnson 1981) demon-
strate that group discussion aimed at clarifying Medical students given the problem to consider
one’s own point of view and being confronted are led to the structure and functioning of the
with other perspectives stimulates epistemic skin, to study the effects of severe burning of the
curiosity in subject matter. skin and to understand the mechanisms ofpain in
To what extent do these principles of learning such a case. O n the other hand, a problem such as
apply to problem-based learning? We will deal the following:
with this question in the next section.
Playing tennis
You’ve been playing a game oftennis among friends. I t
Problem-based learning: analysis of the is a warm and sunny day. Unfortunately, you lose the
exciting game. When you walk home, you notice that
learning process you are wet all over your body, your face feels hot and
looks scarlet and your leg muscles begin to ache.
Problem-based learning was originally
Please explain.
developed at the Faculty of Health Sciences of
McMaster University around 1965. Its origina- would induce students to study in depth the
tors, among them John Evans, Bill Spaulding, physiology of effort including thermoregu-
Bill Walsh, Jim Anderson and Fraser Mustard lation. Students are trained to deal with such a
428 H. G. Schmidt

problem first by activating available prior know- ciples or mechanisms underlying the visible
ledge. Therefore the problem is discussed first phenomena, which may help them understand
without reference to the literature (Barrows & more complex problems presented subsequently
Tamblyn 1980; Schmidt 1983a). and which in the final analysis may support the
Goals of this preliminary discussion are four- management of these problems when
fold. First, it will help students mobilize what- encountered in professional practice. The con-
ever knowledge is already available. The struction ofsuch semantic networks, tuned to the
importance of activation of prior knowledge in situation-at-hand, is the goal of PBL.
the comprehension of new information has In summary, it is proposed here that PBL as an
already been stressed. Activation of prior know- approach to learning and instruction has the
ledge focuses the learning effort and facilitatesthe following cognitive effects on student learning:
understanding ofnew concepts to be mastered. If (1)Activation of prior knowledge -the initial
appropriate knowledge is not activated for some analysis of a problem stimulates the retrieval of
reason, new learning will not take place or will be knowledge acquired earlier.
seriously hampered. Second, group discussion (2) Elaboration on prior knowledge through
will help students to elaborate on their know- small-group discussion, both before or after new
ledge. The confrontation with the problem to be knowledge has been acquired; active processing
understood and other students’ knowledge of of new information.
what might explain the phenomena will lead to (3) Restructuring of knowledge in order to fit
enrichment of the cognitive structures of the the problem presented. Construction of an
participants. Third, the knowledge already avail- appropriate semantic network.
able at this point becomes tuned to the specific (4) Learning in context. The problem serves as
context provided, that is the problem posed. a scaffold for storing cues that may support
Thus, some knowledge restructuring may retrieval of relevant knowledge when needed for
already take place at this point. Fourth, the similar problems.
discussion of a problem is supposed to engage the (5) Since students will tend to see the problems
students in the subject to such extent that episte- presented as relevant and since they engage in an
mic curiosity is aroused to find out in more detail open-ended discussion, epistemic curiosity can
which processes are responsible for the phe- be expected to emerge.
nomena described.
While discussing the problem, students may
encounter issues not well understood. If the
Problem-based learning: research into the
problem is tuned to the level of prior knowledge
basic premises
of the particular group of students, they may
have some understanding but will soon run into The question which of course immediately arises
questions that need answers in order to acquire a is to what extent these premises regarding the
deeper level of comprehension of the problem. cognitive processes underlying problem-based
These questions serve as learning goals to be learning have an empirical basis. In this section a
pursued through self-directed learning. Thus, number of studies will be discussed conducted by
students will review textbooks, articles and other the research group on ‘Cognitive and Moti-
resources in order to build a more comprehensive vational Effects of Problem-based Learning’ of
semantic network of the problem-at-hand. In a the University of Limburg. (This group consists
second round of discussions, students will check of Jan Belien, Maurice de Volder, Willem de
to what extent they now have a more in-depth, Grave, Jos Moust, Bert Kerkhofs, Henk Sch-
more differentiated, understanding of the prob- midt, Steve Foster, Rite Dobbelaere, Herman
lem. This discussion may lead to further elabo- Nuy and Titus Geerlings.) These studies have
ration, restructuring and fine-tuning. been published in Dutch or have otherwise been
Central to the theory proposed here is that poorly accessible to the international health pro-
students while thinking, studying and talking fessions education community. In this discuss-
about the particular problem build a context-sen- ion, we will confine ourselves to the results of the
sitive cognitive structure of the processes, prin- so-called ‘blood-cell-problem studies’.
 Foundations of problem-based learning 429
Activation of prior knowledge. Schmidt (1984) definitely facilitates understanding and remem-
presented small ,groups of students attending bering new information, even ifthat prior know-
higher professional training with the following ledge is only to a small extent relevant to
problem: ‘A red blood cell is put in pure water understanding the problem - and sometimes
under a microscope. The cell swells and even- even incorrect. Interestingly, students who stu-
tually bursts. Another blood cell is added to an died the topic of osmosis a few weeks before the
aqueous salt solution. It shrinks. Explain these experiment was conducted (called the ‘experts’
phenomena.’ A few years prior to this study, the by the authors) did not profit as much by the
students involved had all been acquainted with experimental treatment as compared to the
the subject of osmosis, which is the underlying novices, indicating that problem analysis is most
explanatory mechanism for the phenomena helpful if students have only limited knowledge
described in the problem. Half of the students of the subject.
discussed the blood-cell problem, while the other
Contribution of group discussion to the effect of
halfdiscussed a neutral problem. At a subsequent
problem-based learning. De Grave et al. (1985) have
‘free-recall’ test, the group that had discussed the
compared effects of problem analysis in a small
blood-cell problem remembered almost twice as
group with individual problem analysis and
much information about osmosis as the other
direct prompting of knowledge about osmosis.
group. (Free recall is a procedure in which a
They discovered that small-group analysis had a
subject is instructed to write down everything
larger positive effect on remembering a text than
that he or she remembers about a certain topic
individual problem analysis. Prompting already
without the,.aid of further information. It is
available knowledge relatively had the smallest
considered a measure of both amount and coher- effect. The investigators concluded that the con-
ence of the knowledge a subject has.) This frontation with a relevant problem and small-
demonstrates that problem analysis in a small group discussion of that problem each have an
group indeed has a strong activating effect on independent facilitating effect on prior know-
prior knowledge.
ledge activation relative to direct prompting of
EJects ofprior knowledge activation on theprocess-
prior knowledge. Group discussion had, in par-
ing of new information. Schmidt et al. (1989)
ticular, a considerable effect, suggesting that
presented the blood-cell problem to novices,
elaboration on prior knowledge and learning
14-year-old high-school students who had never
from each other, even before new information is
heard of the subject concerned. Their expla-
acquired, are potent means to facilitate under-
nations therefore mainly had a common-sense standing of problem-relevant information.
character. In an attempt to account for the Moust et al. (1986) demonstrated that the quan-
swelling of the blood cell, one group assumed tity of one’s contribution to the discussion and its
that the membrane probably had valves which quality were unrelated to achievement. This led
would let the water in, but would prevent it from them to the conclusion that the more silent
escaping again. Another group explained the
students were involved in what they called
shrinking of the cell by assuming that salt has
‘covert elaboration’. According to these authors
hygroscopic characteristics. According to them,
it would otherwise be hard to understand how
the salt ‘soaked up’ fluids from the cell in the way these students would profit from the experience.
that it would with a wine-stained table-cloth.
(See also Table 1.) Subsequently, a 6-page text Evidencef o r elaboration and restructuringprocesses.
about osmosis was distributed, both to the To date no data are available which document the
groups that had tackled the blood-cell problem emergence of problem-oriented knowledge
and a control group that had discussed a neutral structures as a result of PBL, that is a result of
topic. The group that had discussed the blood- problem discussion plus individual study. There
cell problem prior to reading the text remem- is, however, some evidence for problem-orien-
bered significantly more about the text than the ted knowledge tuning as a result of problem
group that had studied an unrelated topic. These analysis per se. Table 1 summarizes explanations
findings indicate that activation of prior know- of secondary-education students regarding the
ledge through problem analysis in a small group blood-cell problem.
430 H . G. Schmidt

Table 1. Naive conceptions of processes that are the basis of the blood-cell
~ r o b l e m(taken from Schmidt et al. 1988)
Swelling
The cell is filled with tiny sponges absorbing the water.
The cell absorbs water by means ofan unidentified mechanism because the wall
is porous. However, the wall contains valves that prevent the water from
escaping.
Red blood cells carry oxygen. The cell extracts oxygen from the water and
swells.
The cell contains salts dissolved in liquid. The solution exerts pressure on the
wall larger than the outside pressure exerted by pure water.
The absorption ofwater triggers an unknown chemical reaction within the cell.
Bursting
(6) Blood cells usually take in small quantities of liquids, because the human body
contains many cells. In this particular case, there is only one cell, which has to
absorb too much water.
(7) Animate objects only have a limited life-span.
Shrinking
(8) Water on other fluids is extracted from the cell because of the hygroscopic
properties of salt.
(9) Salt water exerts a higher pressure on the wall than the content of the cell.
(10) The salt corrodes the wall by affecting the wall’s molecules. The cell then begins
to leak.
(1 1) The salt enters into the cell and digests the cell from within.
Swelling and shrinking in combination
(12) The cell contains salt that extracts water from its environment because of its
hygroscopic properties, If the water in the environment contains a higher
concentration of salt, however, fluids will be extracted from the cell.

These explanations were compiled from taped they were asked whether they would like to read
discussions of six groups (some groups produced more about the subjects and whether they were
several explanations). These explanations sug- interested in additional information sent to them
gest that students adapt their general prior know- by the investigators. Before as well as after
ledge to fit the problem-at-hand. The subjects having studied the texts, the groups that had
involved had never before been confronted with tackled the blood-cell problem displayed signifi-
a similar problem; therefore the assumption that cantly larger epistemic curiosity than the group
general world knowledge is indeed restructured that had studied the aeroplane problem. Schmidt
in order to make it suitable for the problem (1983a) found that this higher epistemic curiosity
presented does not seem farfetched. showed itself, among other things, in the fact
Effects of problem-based learning on epistemic that significantly more students participating in
curiosity. In a series of studies by De Volder and the blood-cell discussion had signed up to attend
his colleagues (e.g. De Volder et a l . 1985, 1989), a lecture about osmosis than those who had not
attempts have been made to find out to what participated in that discussion.
extent group discussion about a problem would
increase epistemic curiosity in problem-related
subject matter. Groups were presented with
Discussion
either the blood-cell problem or with a problem
description of a plane taking off from Schiphol Problem-based learning is a relatively new form
Airport. Immediately after the discussion, they of instruction with a long intellectual history. Its
were asked to indicate to what extent they were roots in the philosophies of rationalism and
interested in receiving information about osmo- American functionalism (Dewey 1929) clarify
sis. After having studied a text on the subject, why this approach to learning and instruction
 Foundations of problem-based learning 43 1
emerged in conjunction with the cognitive revo- spent on learning, etc. It is necessary therefore to
1'
lu ion in psychology. lt is not purely coincidental
'
thft McMaster University admitted its first batch
supplement laboratory research with studies in
natural contexts. The University of Limburg
of knedical students in its problem-based curricu- research group has made several attempts in this
lum a year before Ulric Neisser's now classic area (Dolmans et a l . 1992;Kokx & Schmidt 1992;
book Cognitive Psychology was published Moust & Schmidt 1992). For an overview see
(Neisser 1967). We have argued that in PBL, a Nooman et al. (1990). Others are also leading the
number of principles of learning are imple- way (e.g. Moore 1991; Blumberg & Michael
mented, considered to be basic to many forms of 1992).
human learning, comprehension and problem-
solving. These principles can be summarized as:
prior knowledge activation and elaboration
through small-group problem analysis; the con- References
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at the Annual Meeting ofthe American Educational
Research Association, San Francisco, 20-24 April.
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verbal participation in small-group discussion on a u t h o r 4 N o v e m b e r 1992; 12 February 1993; accepted
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