Addressing Nonscientific
Presuppositions in Genetics
Using a Conceptual Change
Strategy
N. M. MBAJIORGU, N. G. EZECHI, E. C. IDOKO
Department of Science and Computer Education, Enugu State University of Science and
Technology, Enugu, Nigeria
Received 6 July 2006; revised 4 December 2006, 21 December 2006;
accepted 22 December 2006
DOI 10.1002/sce.20202
Published online 6 February 2007 in Wiley InterScience (www.interscience.wiley.com).
ABSTRACT: Researchers are becoming aware of the influence of students’ presuppositions in directing their construction of science concepts. When these are entrenched and
drastically nonscientific, they predispose the children to alternative explanatory frameworks
that are inhibiting, especially in a knowledge domain such as genetics. In this study, we
identified such nonscientific presuppositions among 17- to 18-year-old secondary school
students from the Igbo community of Southeastern Nigeria. We designed a research-based
instructional model to address these presuppositions. The relationship between the levels
of nonscientific presuppositions held by students and their achievement in genetics was
assessed. Finally, the effect of the instructional model on students’ relinquishing these nonscientific presuppositions and on their achievement was determined relative to a comparison
group. It was found that this group of students had nonscientific presuppositions that they
used in explaining genetic phenomena, and that the present instructional model aided the
students in relinquishing these nonscientific presuppositions to a great extent. We conclude
that a conceptual change model that addresses explicitly nonscientific presuppositions will
C 2007 Wiley Periodicals, Inc. Sci
lead to an increased understanding of science concepts. Ed 91:419 – 438, 2007
INTRODUCTION
Science and science education are now believed to be cultural activities (Baker & Taylor,
1995; Fang, 2005; Maddock, 1981). The existence of specific ethos, values, attitudes,
mores, and language within the scientific community and the subgroup of science education
distinguish the scientific culture from any other. Central to every culture is the pervasiveness
of certain worldview presuppositions. These presuppositions predispose its members to
Correspondence to: N. M. Mbajiorgu; e-mail: [email protected]
C
2007 Wiley Periodicals, Inc.
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think and act in specific ways. Combined with the shared experiences of its members,
meaning structures and models develop, which are used in the observation, description,
and explanation of natural phenomena (Mbajiorgu, 2003). These models quite often have
predictive and explanatory powers. This is true of the culture of science as well as that
of others. Since science is a global activity it often has to interact with other cultures.
This interaction introduces some friction, especially in the classroom where children are
expected to jettison models that have served them well in order to embrace the culture of
science. Many children set up cultural boundaries (Aikenhead, 1996; Jegede & Aikenhead,
1999) and prescribe conditions that direct their actions within each.
The laws and theories of science have an advantage over other nonscientific laws and
theories in that they are built with the help of instruments that extend the range of human
observation. They, therefore, traverse the macro level of phenomena to the micro. This
attribute of science coupled with its reliance on a hypothetico-deductive experimental
approach to problem solving as well as its focus on the measurable attributes of phenomena
make its claims testable and replicable. Although this cannot be said of other explanatory
frameworks, they have nonetheless proven powerful over a wide range of phenomena and
time, thereby both possessing scope and providing force to the users (Cobern, 1996a,
1996b). Educational researchers have come to realize that alternative explanatory models
and worldview presuppositions form the knowledge base (Driver, 1983; Driver, Guesne, &
Tiberghien, 1985a, 1985b), discriminatory networks (Gobet et al., 2001; Gobet & Simon,
1996), and perception filter (Johnstone, 1991) through which incoming information is
perceived and processed.
Research into students’ understandings of genetic concepts offers a typical example
of this assertion. Genetics has been identified as one of the most difficult concepts in
biology (Bahar et al., 1999a, 1999b; Banet & Ayuso, 1999; Johnstone & Mahmoud, 1980;
Mysliwiec, 2003; Tsui & Treagust, 2003, 2004). In line with the above argument, one of
the sources of this difficulty is children’s prior conceptions and worldview presuppositions
(Mbajiorgu, 2000). A number of studies have been done that explored the conceptual
change approach to handle these prior conceptions. Venville and Treagust (1998) found
that although there was progress in students’ shifting from a wrong ontological model of
the gene to a right one, and a better epistemological grasp of the nature of the gene, this
progress was mediated by the social and affective context of the classroom environment.
These contextual factors were such that they did not allow a full ontological change nor
encouraged progression from one end of the epistemological continuum to the other, that
is, from being intelligible to being fruitful. They concluded that the majority of the students
did not progress to more sophisticated conceptions about the gene.
In another study, Tsui and Treagust (2003, 2004) explored remediating students’ difficulties from another perspective. Their methodology implicated the nature of genetic concepts
as the source of difficulty. Johnstone (1991) contends that people are familiar with concepts
that are made up of tangible instances and are therefore perceived by the human senses
without the aid of instruments. But concepts such as genes, DNA, and chromosomes are not
easily perceptible. They are thus difficult to construct. Worse still, these concepts traverse
the macro, micro, and symbolic levels of thought. In the study of dominance of genes,
the macro level involves visible phenotypic features such as “widow’s peak” and tongue
rolling for instance. This is as a result of the micro phenomenon of two recessive genes being present in the genotype. It can be expressed symbolically with genetic crosses. Students
are expected to learn genetics at these three levels simultaneously. Johnstone wondered
why science would not be difficult to learn in the classroom under these circumstances.
To aid students’ understanding, bearing in mind the nature of genetic concepts as described above, Tsui and Treagust used an interactive model, BioLogica (Tsui & Treagust,
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ADDRESSING NONSCIENTIFIC PRESUPPOSITIONS IN GENETICS
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2003), that “features multiple, dynamically linked representations of genetics at different
levels of organisation: DNA, genes, chromosomes, cells, organisms and pedigrees” (p. 111).
BioLogica, they claim, enhances students’ understanding of genetic concepts by providing complementary ideas and processes and constraining interpretations. By implication,
their conclusion in the 2003 study was that shared meaning making is highly important in
classroom learning of genetic reasoning.
Conceptual Change
From the studies above, it does appear that prior/alternative conceptions have important
roles to play in the understanding of genetic concepts. Cognitive psychology has revealed
that there has to be a threshold of prior knowledge that ought to serve as an anchor for incoming information for learning to be effective. Depending on the nature of this prior/alternative
conception, the interpretation of incoming information may either be wrong or right, or even
a hybrid. This has led to the constructivist paradigm that sees the individual as negotiating
knowledge, and constructing personal realities that make sense to him (Cobern, 1966a,
1996b). Children are thus actively constructing and reconstructing knowledge in the light
of their experiences. Learning therefore becomes a matter of revising existing knowledge
structures (Savinainen, Scott, & Viiri, 2004; Vosniadou, Ioannides, Dimitrakopoulou, &
Papademetriou, 2001).
This perspective of learning has found expression in schools through the conceptual
change approach/strategies. Posner, Strike, Hewson, and Gertzog (1982) posit that before
there can be conceptual change, the cognizing individual must first find an idea intelligible,
plausible, and fruitful as well as being dissatisfied with a competing conception. In the
studies reviewed briefly above, although the knowledge presented was rational and logical
and strategies were carefully thought out, planned, and implemented, the students did not
get to the stage of finding the new information fruitful and thus meaningful learning did not
occur. This has led some science education researchers, such as Vosniadou et al. (2001), to
claim that interpretation of scientific information by children is largely constrained by a few
entrenched presuppositions. They contend that entrenched presuppositions (deep theoretical
constructs) are more difficult to change than relatively superficial observations. And children
are often not aware of these. Conceptual change to them therefore involves change in specific
beliefs and presuppositions as well as “the development of metaconceptual awareness and
the construction of explanatory frameworks with greater systematicity, coherence, and
explanatory power” (Vosniadou et al., 2001, p. 388).
A Case for Beginning From Presuppositions
Classical conceptual change as proposed by Posner et al. (1982) assumes that the learner
is a rational being and so will always respond to logical and rational information. It fails to
take into consideration the idiosyncratic ways the learner comes to know and other factors
such as motivation (Pintrich, Marx, & Boyle, 1993), worldviews (Cobern, 1996b), and
other social factors (Tyson, Venville, Harrison, & Treagust, 1997) in conceptual change.
Research evidence such as is presented in this study and others suggests that classical
conceptual change theory is not always effective in bringing about conceptual change.
Thus, Vosniadou et al. (2001) claim that the interpretation of scientific ideas by children
is often constrained by a few entrenched presuppositions. For instance, Vosniadou and
colleagues carried out a study to determine the representations of the earth held by children.
They found that children have difficulty making correct representations of the spherical
shape of the earth and the region of the earth where people live. The difficulty is attributed
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MBAJIORGU ET AL.
to the presupposition that space is organized in terms of the direction of “up” and “down”
with respect to a flat surface, and that unsupported objects fall in a “downward” direction
(Vosniadou et al., 2001, p. 387).
They listed a number of alternative conceptions that children have about the shape of the
earth and the part of the earth that people live. They also listed constraining presuppositions
in the areas of neo-Darwinian theory of evolution and force. Children’s knowledge base
is seen as being a function of a number of interrelated observations, beliefs, and presuppositions and that these form a fairly coherent system of explanatory framework. They
distinguish between two types of beliefs and presuppositions: those easy to change and
those more difficult to change. The former are formed from superficial observations while
the latter are formed from theoretical constructs and are entrenched and very difficult to
change. Vosniadou and colleagues contend that alternative frameworks are derived from
these presuppositions in order to explain natural phenomena. Where more than one presupposition underpins a phenomenon, models developed to explain the phenomena are often
synthetic.
It is argued that students are often not aware of the beliefs and presuppositions that
constrain their reasoning. Awareness on the other hand does not guarantee the understanding
of these as theoretical constructs; rather students often conceive them as facts about how
the physical world works. The first step in conceptual change efforts seem to us to logically
begin from making students aware of the presuppositions they hold and their nature.
Alternative conceptions are only the results of interpretations based on these; as such, any
change in the presupposition of the students will in the long run result in the change of the
alternative conceptions and a better comprehension of scientific facts.
Many researchers have demonstrated in the area of genetics that the students’ preinstructional ontological conceptions of the gene is as “matter” and not as “process,” that is,
involving a series of sequences of instruction that influence the phenotype of the organism
(Tsui & Treagust, 2004; Venville, Gribble, & Donovan, 2005; Venville & Treagust, 1998).
This categorization of the gene agrees quite well with a presupposition assigning explicable
phenomena, e.g., resemblance of siblings, hair color, eye color etc. to kinship (Santos &
Bizzo, 2005). On the other hand, it contradicts the theory of variation, especially of extreme
cases as might be found in mutations or genetic disorders. Shiloh, Rashuk-Rosenthal, and
Benyamimi (2002) in a study seeking to determine the classification of illness causes found
that mutated gene and chromosomal abnormality obtained the lowest mean scores out of
the 42 illness causes studied. They claimed that people (sometimes including biological
researchers) attribute illnesses caused by genetic/biologic causes to chance and mystical
forces. Therefore the theory of kinship explains heredity, whereas chance and religious
beliefs explain variation and abnormalities.
Venville et al. (2005) point out that popular culture has a great impact on how children
understand genetics. Santos and Bizzo (2005) concur stating that lay or everyday knowledge
plays fundamental roles in influencing people’s decisions about genetic phenomena and
that this is premised on the social concepts of kinship. In their study, they found that one of
the families they studied with an inherited disease, neurofibromatosis, explained the disease
by the theory of kinship because it was present through many generations. This family did
not associate the benign tumors with a disease but rather referred to it as birthmarks. In
cultures such as the one from which the participants of the present study were drawn,
the explanatory framework of a deity intervening in human affairs often underpins many
cause–effect phenomena in students’ knowledge structures (Mbajiorgu & Anolue, 2000).
Mbajiorgu (2000) found that the spiritist worldview underpinned students’ preferences
for the courses of action suggested when presented with stories of genetic disorders. The
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findings of these studies demonstrate that presuppositions and popular culture (which
precipitates into presuppositions) indeed influence students’ and lay people’s decisions and
understanding about genetic phenomena. Solomon and Johnson (2000) agree and argue
that in non-Western cultures, radically different understandings of inheritance and kinship
do exist.
In the present study, we decided to use an instructional programme based on conceptual
change strategies. However, rather than start at students’ prior/alternative conceptions,
we began from the presuppositions by presenting them with everyday phenomena that
have genetic origins but have underlying nonscientific presuppositions or are based on
popular culture. Specifically, this study sought to assess the extent to which students
adhere to nonscientific presuppositions regarding genetic phenomena in the Igbo culture
of Southeastern Nigeria before and after instruction; second, it assessed the relationship
between the level of presuppositions and students’ achievement; and finally, it considered
the effect of the present instructional strategies on students’ understanding of genetic
concepts in relation to a comparison group.
METHODOLOGY
This study sets out to determine whether students involved in an intervention package
based on the conceptual change theory will perform better than a comparison group taught
using the traditional method of textbook sequencing and whether the intervention had any
effect on the level of nonscientific presuppositions held by these students. We also sought to
determine whether the level of nonscientific presuppositions held by these students played
a role in their achievement in genetics.
Design
A quasi-experimental research design of the pretest –posttest nonequivalent control group
was adopted for this study. We selected four single-sex schools from an urban town (Enugu)
in Southeastern Nigeria because the same worldview presuppositions are prevalent among
the students (Mbajiorgu, 2000). By simple random sampling, we assigned intact classes
from each of the schools to the experimental or the comparison group. Altogether, 282
students (aged between 17 and 18 years) from Southeastern Nigeria were involved in the
study. These were in their final year of secondary school. The choice of this level of
education was based on the fact that the students have all taken some introductory lessons
on Mendelian genetics (basic terms and concepts in genetics, e.g., chromosomes, genes,
alleles), mitosis, and meiosis in their first 2 years of senior secondary school. The subjects
were tested before commencement of treatment and immediately after treatment.
Cultural Characteristics of the Participants. The participants are all members of the
Igbo tribal group of Southeastern Nigeria. This culture is strongly patrilineal. The male
child alone is regarded as the true child while the girl child is perceived as a mere addition
to make up the number (Obi, 2006). Closely related to this is the nature of the marriages.
Polygamous marriages quite often arise as a result of the need for male children, even among
educated people. The belief is that the woman has a greater role to play in determining the
sex of the children.
It is customary to attribute illness causes and explanation of inexplicable phenomena (e.g.,
sickle cell disease and albinism) to mystical forces (Nzewi, 2001) and unusual etiological
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theories (Okoro, 1975). This is because the entrenched presupposition of deities intervening
in the affairs of men is prevalent. Mbajiorgu and Anolue (2000) and Mbajiorgu (2000)
working with secondary school students in this culture empirically demonstrated this to
be the case. These presuppositions lead to many stereotypic perceptions and alternative
interpretations (Mbajiorgu, 1999; Mbajiorgu & Iloputaife, 2001) among the students and
the people. In a preliminary study, Mbajiorgu (2000) worked with secondary school students
in this culture to identify some of the worldview presuppositions underpinning some genetic
phenomena. The results agree with the findings of Nzewi (2001), Obi (2006), and Okoro
(1975).
If we go by the categorical claims of Vosniadou et al. (2001) that many alternative
frameworks can be traced to a few entrenched presuppositions, it will not be surprising for
students from this culture to have a high level of alternative conceptions that will hinder the
understanding of genetic concepts. It is also expected that the higher the level, the poorer
the performance of the students in this domain of knowledge. The present study is therefore
relevant as it will test the validity of these claims. This forms the major thrust of the
study, i.e., to address specifically the nonscientific presuppositions rather than individual
alternative conceptions.
Control of Extraneous Variables
To control subject or treatment interaction, we made sure that each time a lesson was
going on in the classes involved in this study, all the other classes of the same grade
were also involved in similar classroom activities. To eliminate the errors arising from
the nonrandomization of research subjects, we used ANCOVA in analyzing the data
on achievement. This corrected the error of initial difference in the knowledge of the
students, thus removing the biases that may have been introduced by the use of intact
classes.
The second author scripted the lesson notes that were used for the lessons. With this, we
trained four teachers, who were the regular class teachers of biology in the schools selected.
This consisted of explaining the meaning of conceptual change, alternative conceptions,
and presuppositions. Particularly, the roles of motivational factors as well as metacognition
on the science learning process were emphasized. They were led to consider the differences
between the treatment procedure and their normal teaching procedure, which was what the
comparison group were subjected to. They were then taken step by step through the lesson
notes and shown how to manipulate the students at each stage. The teachers then taught
equivalent groups during a pilot study period after which the strengths and weaknesses of
each teacher were extensively discussed.
The pilot study also served to identify nonscientific presuppositions existing among this
cohort of students and to compare these with already empirically identified nonscientific
presuppositions from similar cohorts. The results were also used in the development of the
instrument. By using the regular class teachers, we avoided performance being influenced
by the subjects’ knowledge of being involved in the research. To avoid novelty effect, all
the classes for ages 17–18 years in the schools selected were involved at every stage of the
research, thereby giving no hint that something different from normal teaching was going
on. The teachers taught the experimental and comparison groups in their schools. Each
class received a total of eight lessons and each lasted 70 minutes. The topics selected were
mutation, sickle-cell anemia, albinism, and sex determination. This is because these phenomena have nonscientific presuppositions underpinning them (Nzewi, 2001; Obi, 2006;
Okoro, 1975).
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Identification of Underpinning Presuppositions
We made up fictitious stories with the phenomena selected for study. Each story involved a hypothetical case. The pilot study group of students were presented with these
stories and asked in a free response format to state what they thought were the causes
of the phenomena and in each case, what they would advise the affected individuals
(see Appendix A for sample hypothetical cases and excerpts of students’ responses). We
categorized the responses into scientific views, popular culture, and nonscientific presuppositions (see Appendix B for categorization of responses). Take, for example, sickle cell
anemia, which the people from the area under study associate with a phenomenon called
ogbanje.
Usually people from this area do not test themselves for sickle cell. As a result, individuals
who are carriers end up marrying each other. The consequence is usually tragic. In many
cases, the couples may lose a number of their children in infancy. In the culture where this
study was carried out, such an incident is interpreted as an ogbanje phenomenon (Nzewi,
2001). It is believed that a demon spirit, ogbanje, possesses the children and causes them
not to want to live on earth. As a result, the first child to die reincarnates in a subsequent
child, who in turn dies, and so on. Such deaths are believed to recur except where the
parents perform some rites in order to appease the gods. These rites are believed to stop
further deaths.
In a study, Nzewi (2001) examined culturally defined symptoms of 100 children who
were classified by relations as malevolent ogbanje. She found a concordance between
culturally accepted descriptions of malevolent ogbanje and symptoms of sickle cell disease.
She claimed that there is a cultural resistance to sickle cell disease as an explanation for
malevolent ogbanje.
Again, it is customary in this culture for a man to marry a second wife and if necessary
more than two wives in the case of failure of the earlier one(s) to give birth to a male
child. Being a highly patrilineal society, the absence of a male offspring is unacceptable
(Adeyokunnu & Adeyeri, 1978; Obi, 2006).
Obi (2006, p. 1) puts it succinctly, “the position of a wife in her husband’s family remains
shaky and unpredictable until she begets a child. She becomes really secure after the birth
of a male child.. . . In fact, the birth of the child gives her the title of wife, before this time
she may be said to be a wife in anticipation.” Popular culture implicates the woman in sex
determination. Students are thus often guided by this rather than genetic principles in their
explanations of sex determination.
Okoro (1975) in a study of 1000 albinos in Nigeria claimed that “nowhere in the traditional
views on albinism is it believed to be associated with inbreeding. Rather, weird etiological
theories range from punishment from the gods, to conception during menstruation, or to
seeing frightening sights during pregnancy” (p. 491) and extramarital relationships. In fact,
popular culture refers to women’s wombs variously as afo oma (beautiful womb) for a
woman whose children are usually beautiful or handsome, or afo ocha (white womb) for a
woman whose children are fair or albinos. Again, these form strong explanatory frameworks
for the students. See Appendix A for sample student responses to likely causal attributions
to genetic phenomena.
Design of Intervention Package
Vosniadou et al. (2001) outlined a number of principles to be considered in the design of
learning environments. We took these into consideration in designing the intervention for
this study. This we did in the following ways:
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1. Order of the Acquisition of the Concept Involved. In the area of genetics, research
has shown that students’ prior ontological conception of the gene is as a thing passed on
from parents to offspring. Seen as matter rather than as a sequence of instructions, it is
difficult for the children to comprehend the process of mutation or variation, which may
arise from one generation to another. This was taken care of at the points where students
considered how the anomalies in this study arise during gametogenesis.
2. Identifying Students’ Presuppositions. In genetics, certain phenomena are counter-
intuitive. It is difficult for students to understand how an offspring can be an albino when
no known member of the familyis an albino. The presuppositions that such inexplicable
phenomena are because there is an all-powerful God intervening (blessing and cursing as
the case may be) in the affairs of man and that extramarital affairs are the sources of such
phenomena were taken into consideration during the discussions. The theory of kinship was
also challenged and the concept of dominance and recessiveness of genes was emphasized.
These and other presuppositions were identified from the onset by students responding to
the hypothetical stories.
3. Facilitating Metaconceptual Awareness. In the culture in which this study was done,
an entrenched belief is that scientists do not believe in God (Mbajiorgu, 1999; Mbajiorgu &
Iloputaife, 2001). An attempt to bring students into a correct conception of a scientific truth
often meets with resistance because of this. In this study, we addressed this explicitly and
challenged their explanatory framework based on their belief in deities. We made use of
examples and, occasionally, referred to religious documents as scaffolds. We aided them in
understanding the setting of boundary conditions between religion and science. Students
were challenged to air their views and to reconsider them by comparing them to the views
of others and available evidence.
4. Motivation for Conceptual Change. We motivated the students toward conceptual
change by presenting them with phenomena that are pervasive in their environment. We
also used the terms that are used in their social environment, such as ogbanje, onyenzuzu
(used for an imbecile or people with different forms of mental retardation), that are relevant
for some of the phenomena addressed in this study. By presenting different cases, the
students’ presuppositions and prior conceptions were challenged. They were asked to also
think of examples where these phenomena had been experienced and to reflect on these in
view of their present understandings. They were encouraged to reinterpret such phenomena
and prescribe possible courses of action for the affected individuals.
5. Provision of Models and External Representations. We used and required students
to use symbols in the genetic crosses as well as in exercises during the course of the
lessons. Following the above considerations, we adapted the five-step instructional model
of Stofflet and Stoddart (1994). These steps include (1) determination of prior conception, (2) exploration of the phenomena, (3) discussion of the results of the explorations,
(4) development of dissatisfaction with prior conception, and (5) application. The model
also accommodated adequately the principles suggested above. Each class received eight
lessons of double periods (70 minutes). We will use the topic of mutation to give an example
of the instructional procedure.
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Instructional Procedure
Step I: Determination of Nonscientific Presupposition. The students were engaged in
a discussion prompted by the following three presentations.
Case I. A couple, Mr. And Mrs. Oliseh, had a child. At birth, the child had the physical characteristic of a female, i.e., female genitalia. However, as the child grew, she
developed male characteristics. These included deep voice, flat chest, and no ovulation or
menstruation.
Case II. Another couple, Dr. and Mrs. Uwaonu, not related to Mr. and Mrs. Oliseh also
had a child. Their case seemed to be the opposite of the earlier case in that the child had
the physical characteristic of a male, i.e., male genitalia. As the child grew, he developed
female secondary characteristics, e.g., growth of the breast.
Case III. Mr. and Mrs. Nwachukwu experienced a different problem, in that their child’s
growth was retarded. This retardation affected both the child’s physical and mental growth.
What could be the cause of these problems seeing none of the couples were related? And
what will be your advice to the couples?
At this stage no view expressed by the students was accepted or rejected. The teacher
probed to grasp the children’s ontological views as well as the underpinning presuppositions
that are serving the students as bases for explanatory frameworks.
Step II & III: Exploration of the Phenomena and Discussion of the Results. The
students were required to carry out the genetic crosses in the first two cases above. They
did this, using appropriate symbols, e.g., Figures 1 and 2. This was designed to challenge
their initial presuppositions and sensitize them to chromosomal mutations. The students
were asked to use their knowledge of meiosis and segregation to discuss the anomalies they
identified from the genetic crosses. They were also allowed to discuss what they thought was
the consequence of their observations. Every ramification of this kind of genetic aberration
was discussed and the students undertook as many exercises on chromosome crosses as is
required at this level in the curriculum.
Cross I
XY
Parents
Gametes
F1 Generation
XX
X
Y
XXX
XXY
XX
X
Figure 1. Cross of a case in which the female sex chromosomes failed to separate.
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Cross II
XY
Parents
Gametes
F1 Generation
XX
XY
XXY
X
X
X
XXY
X
Figure 2. Cross of a case in which the male sex chromosomes failed to separate.
The emphasis was that as gametogenesis occurred, problems such as failure of homologous chromosomes to separate, recombination of genes, and crossing over could lead to
genetic disorders.
Step IV: Development of Dissatisfaction With Presuppositions. Each of the cases
above, as well as their phenotypic manifestations, was discussed. They were concretely
linked to the stories that were presented at the beginning of the lesson. The students were
asked to reexamine the views they had put forward at the beginning and to state their new
views, if any, with justification(s). A discussion of the different viewpoints ensued and the
students were expected to accept or reject each other’s views based on their understanding
of the nature of the inheritance substance as is evident from their exercises. The applications
of the knowledge of mutation in medicine and agriculture were also discussed.
Step V: Application to Other Life Situations. Other kinds of disorders frequently en-
countered in this locality were also presented in story form and the students were asked to
discuss what they thought the causes of the problems were and a possible course of action
in each case. The second requirement was very vital because Mbajiorgu (2000) found that
students’ (of those from this locality) understanding of genetic phenomena were often not
fruitful. They could fully explain the scientific principles involved in the phenomena but
took recourse to a nonscientific principle in prescribing a course of action to solve the
problem. They were therefore probed to see if the views stated earlier had progressed from
only seeking spiritual help to more fruitful actions such as seeking genetic counseling or
doing both.
For the control group, instruction consisted of using the textbook sequencing approach.
Take for instance the lesson on mutation, in which instruction involved five steps:
Step I: Introduction including a revision of earlier lessons on genetics, e.g., revisiting
briefly the concept of chromosome
Step II: Meaning of chromosome mutation
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Step III: Examples of chromosome mutation
Step IV: Application of knowledge of chromosome mutation
Step V: Summary and closure
In both groups, the objectives of the lessons remained the same: (1) define mutation,
(2) state the effects of mutation, (3) explain the concept of chromosome mutation, (4) give at
the least three examples of chromosome mutation, and (5) give instances of the application
of the knowledge of chromosome mutation.
Instruments for the Collection of Data
Two instruments were used in the collection of data, an instrument measuring the level
of presuppositions possessed by the students (presupposition instrument; PI) and a biology
achievement test. PI yielded categorical data, whereas the achievement test yielded numeric
data.
The PI. During the pilot study, students were told the same stories as in the intervention.
They were required to respond to these in a free response format. (See Appendix A for examples of students’ responses.) The responses were considered carefully and then categorized.
Three categories emerged: scientific position, popular culture, and metaphysical/spiritist
position. (See Appendix B for sample items and the categorization of the alternatives.) We
adopted these categories in the PI. The PI therefore was a 12-item instrument. Each item
has three alternatives for students to choose from: an alternative expressing the scientific
view, one expressing popular culture, and another that expressed a presupposition, whether
spiritist or metaphysical. Since these were originated from students’ viewpoints, we assumed the instrument to be valid. Aikenhead and Ryan (1992) contend that empirically
developed instruments possess inherent validity/reliability since the items are not derived
from theoretical positions but from students’ reasoned viewpoints.
Biology Achievement Test. This was a 40-item achievement test. Each item has four
alternatives from which the students chose. A test blueprint was developed taking into
consideration the topics that were covered in this study. With this a content validity was
carried out, while the three authors as well as the four teachers involved in the study carried
out a face validity of the test. A reliability estimate done with the Kuder –Richardson formula
20 (K-R 20) gave a coefficient of 0.82, indicating the instrument has a high reliability.
Data Analysis
As explained above, the PI is a 12-item instrument, each item having three alternatives
from which the students were expected to make a selection. If a student chooses a scientific
option, the response is assigned a score of 1 and if any of the other two options, the response
is assigned a score of 2. The lowest score obtainable on the PI is therefore 12 and the highest
24.
To categorize the students and for rigorous analyses on which inferences can be based
we adopted a three-level categorization scheme by dividing the range between 12 and 24
into three levels. Thus students scoring 12–15 were low in presupposition, those scoring
16–19.5 were intermediate, and those scoring 19.6–24 were high in presupposition. For
the genetics test, a right response was given a score of 1 and a wrong response the score of 0.
Science Education DOI 10.1002/sce
430
MBAJIORGU ET AL.
To determine the role of the level of nonscientific presuppositions on achievement in
genetics we constructed a boxplot of the data from PI against the scores from the achievement test. To determine the effect of the intervention on the level of presupposition, we
did a cross tabulation with chi-square statistics and tested the value for significance at
P < .05. Finally, a 2 × 3 analysis of covariance (ANCOVA) was done to compare the mean
scores of the experimental group students with the mean scores of the comparison group
students. The main effects were, therefore, method and presupposition levels. To confirm
the detected trends from these analyses, we ran analyses of covariance for the experimental
and comparison groups separately, with presupposition levels as the main effect.
RESULTS
The boxplot (Figure 3) reveals that the low-presupposition group did better than the
intermediate group, which in turn did better than their high-presupposition counterparts.
The same is true of the distribution of the scores for each group. The low-presupposition
group has a wider distribution than the intermediate group, which in turn has a wider
distribution than the high-presupposition group. Again we notice from the boxplot that
the distribution for the low-presupposition-level group is skewed toward the bottom while
the reverse is the case for the intermediate-presupposition-level group. The box for the
high-presupposition group is very close to being normal. This indicates that the scores of
majority of the students in the low and intermediate groups are identical. For each of these
two groups, there are outliers. Candidate numbers 137 and 57 belonging to the intermediate
group scored 35 and 33, respectively, whereas the outlier in the low-presupposition group,
candidate 51, had a score of 5.
At the pretest stage, all the students had high levels of nonscientific presuppositions. At
the point of the posttest, that had changed. The cross-tabulation and chi-squared statistics
(Table 1) done for the posttest scores on the levels of presupposition reveals that for the
experimental group students, all but one student had moved from a high presupposition
level to intermediate (28) and low (109) presupposition levels. For the comparison group
Posttest Achievement Scores
40
137
57
30
20
10
51
0
N=
127
69
87
Low
Intermediate
High
Presupposition Level
Figure 3. Boxplot of all the students by level of presupposition against posttest achievement scores.
Science Education DOI 10.1002/sce
ADDRESSING NONSCIENTIFIC PRESUPPOSITIONS IN GENETICS
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TABLE 1
Cross Tabulation of Scores of Students by Presupposition Levels and
Chi-Square Tests of the Posttest Scores
Presupposition Level
Experimental group
Count
Expected count
Comparison group
Count
Expected count
Total
Count
Expected count
High
Intermediate
Low
Total
Chi-Square
Significance
1
42.4
28
33.6
109
61.9
138
138.0
150.619
.000
86
44.6
41
35.4
18
65.1
145
145.0
87
87.0
69
69.0
127
127.0
283
283.0
students, only 41 and 18 had moved from high presupposition to intermediate and low
presupposition levels respectively. The chi-squared statistics gave a value of 150.62, which
was significant at .000 (df = 2). This is indicative of the influence of the intervention in
students’ relinquishing the nonscientific presuppositions that they held.
A 2 × 3 analysis of covariance using group (experimental and comparison) and presupposition level (low, intermediate and high) as main effects reveals that both variables were
significant (see Table 2). However, the interaction effect was not. The adjusted R-squared
figure of .703 shows that the variables together explain 70.3% of the variation between the
students.
Analysis of covariance done separately for the experimental and control groups with
level of presupposition as the categorical variable (not reported here in tabular form)
showed the differences in the scores of the students to be significant (Experimental group:
F = 4.92, df = 2, P < .05, R 2 = .32; Comparison group: F = 45.85, df = 2, P < .05,
TABLE 2
2×3 ANCOVA of Achievement Scores by Treatment and Presupposition
Level
Source of Variation
Corrected model
Intercept
Preachievement
Treatment
Presupposition level
Treatment × presupposition
level
Error
Total
Corrected total
Sum of
Squares
df
Mean
Square
F
112.246
336.301
70.670
8.555
13.397
.674
13878.733
6930.344
1456.339
176.296
552.143
27.771
6
1
1
1
2
2
2313.122
6930.344
1456.339
176.296
276.072
13.885
5687.691
133849.0
19566.424
276
283
282
20.608
Note: R 2 = .709 (Adjusted R 2 = .703).
Science Education DOI 10.1002/sce
Significance
.000
.000
.000
.004
.000
.511
432
MBAJIORGU ET AL.
R 2 = .58). However, examination of the sums of squares indicates that the variation
explained by presupposition level was larger for the comparison group (1426.1) than for
the experimental group (254.64) students. This is especially significant when compared to
their sums of squares explained by error (Experimental: 3469.53; Comparison: 2084.02)
and when the R 2 values are considered.
DISCUSSION
The results of this study indicate that students from the Igbo culture of Southeastern
Nigeria have nonscientific presuppositions that form explanatory frameworks in their interpretation of genetic phenomena. Thus, phenomena that cannot be accounted for by the
theory of kinship were attributed to spiritual forces (e.g., Klinefelter’s syndrome attributed
to curses or the recurrent death of children at infancy attributed to the ogbanje phenomenon)
or by behavioral or cultural patterns (e.g., a mother of an albino having extramarital affairs
or having afo ocha, respectively). This view seems to be quite pervasive among the secondary school students and can be explained by what many researchers (Duit & Treagust,
2003; Tsui & Treagust, 2003, 2004; Venville & Treagust, 1998) have found about children’s
ontological categorization of the gene. Children tend to perceive the gene as a passive particle rather than an active particle that contains a sequence of instructions that are able to
influence the characteristics of organisms.
Viewed in this way, genes are transferred whole giving no room for wrong/different
instructions as might be obtained in a biochemical process. Any extraordinary phenomena
or extremely variant phenomena cannot therefore be accommodated by their conception.
The fact that these conceptions often are acquired through popular culture and everyday
experience (Banet & Ayuso, 1999; Santos & Bizzo, 2005) and have served these children
well make them entrenched. Given the monoistic (monoism: the practice of worshipping
one God while acknowledging the existence of other gods) outlook of this culture, they
resort to explanations upholding a divine origin.
It would seem, therefore, that cultures play a role in the formation of explanatory frameworks used by students (Thijs & van den Berg, 1995). Santos and Bizzo (2005) found that
their subjects did not use explanations based exclusively on divine origins but on folklores
that propagated a “contamination explanatory model.” The subjects in the present study
(like Santos and Bizzo’s subjects), to a large extent, did not recognize the genetic origin of
many of the phenomena prior to instructions for the experimental group students and even
after instructions for the comparison group students. They rather promoted the “theory of
divine origin.”
The trend in the boxplot is quite revealing and interesting. It does appear that students
with high levels of nonscientific presuppositions did less well than those with lower presupposition levels. The small spread of scores in the box for the high presupposition level group
suggests that presupposition level may be an important factor in the performance of students. The variation of students’ scores in this category is low suggesting their performance
may be the result of the level of presupposition.
This is confirmed by the ANCOVA analyses done separately for the two groups. Whereas
the differences in scores between the different levels of presupposition were significant, the
R 2 values and sum of squares resulting from the presupposition levels indicate that the effect
of the presupposition level was smaller for the experimental group than for the comparison
group. This suggests that when the level of presupposition is not reduced, it decreases the
achievement of students and where this is controlled (e.g., by the use of an intervention
package in the present study), it enhances the performance of the students. Performance
Science Education DOI 10.1002/sce
ADDRESSING NONSCIENTIFIC PRESUPPOSITIONS IN GENETICS
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under such control could then be the result of other cognitive and environmental factors
such as mental capacity, level of embeddedness, psychosocial environment, study habits,
motivation, etc.
The results of the present study suggest that where the method of teaching is not deliberately designed to handle the presuppositions, performance is affected. Santos and Bizzo
(2005, p. 565) in reviewing literature on alternative strategies in the teaching of genetics
and related topics conclude that the investigations they reviewed “aimed at describing the
failure of the teaching–learning process.” Other researchers (Tsui & Treagust, 2003, 2004;
Venville & Treagust, 1998) are not so pessimistic about the outcome of teaching strategies.
They reported that although students did not progress to the stage of fruitfulness, they
nonetheless progressed along the ontological continuum of matter and process, and Zohar
and Nemet (2002) found significantly higher scores for their experimental students when
compared to the controls.
Although we used a quantitative method to analyze our data, we can state that the intervention package used in this investigation had a positive effect on students’ understanding
of genetic concepts as well as on their relinquishing nonscientific presuppositions. This may
be because, as suggested by Banet and Ayuso (1999), we started from observable human
phenomena and progressed to genetic principles, i.e., from a macro to a micro level. It may
also be attributable to the fact that the instructions for the experimental group explicitly
sought to handle these presuppositions among the students. Santos and Bizzo (2005) argue
that the resistance of everyday knowledge is because it is premised on socially shared
empirical evidence and that their subjects’ beliefs were not explicitly taught in schools,
which thereby would have led to their being upheld.
Addressing alternative conceptions or misconceptions without addressing the underlying
beliefs and presuppositions may lead to some progress but not to the desired extent as
demonstrated by Mbajiorgu (2000). Vosniadou et al. (2001) contend that what is needed
for students to abandon their misconceptions and alternative conceptions and by inference
enhance understanding, is for students to change the entrenched presuppositions that gave
rise to the misconceptions.
CONCLUSION
A number of implications emerge from the results of this study. Students from the
Igbo community of Southeastern Nigeria build nonscientific explanatory frameworks in
the explanation of genetic phenomena. These frameworks result from “socially shared environmental evidence” (Santos & Bizzo, 2005) and “provide good explanations of their
everyday experiences, function adequately in the everyday world, and are tied to years of
confirmation” (Vosniadou et al., 2001, p. 393). These arise from the entrenched nonscientific presupposition that promotes the divine origin of inexplicable genetic phenomena.
Science education must seek to explicitly address these presuppositions and help the children form links between their everyday experiences and scientific knowledge. Conceptual
change strategies must go a step further to address entrenched presuppositions. These
presuppositions are fundamental to students’ representations and explanations of physical
phenomena. They also constrain the interpretations of scientific knowledge. Since many
of the studies reviewed in this paper found students did not progress to fruitfulness, and
since the present study was limited to dissatisfaction and intelligibility (plausibility and
fruitfulness were not considered because of the nature of the instruments), it might be
worthwhile to suggest that other works explore the role presuppositions play in conceptual
change.
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MBAJIORGU ET AL.
By far the greatest limitation of the present study is the lack of qualitative data in the
analysis. This was deliberate because we wanted to carry out an exploratory study to
determine the place of presuppositions in achievement; the claims in the present study
should, therefore, be treated with caution by reason of this limitation. It will therefore be
worthwhile to look at students’ progression along the conceptual change continuum and the
role an intervention such as this (that addressed the nonscientific presuppositions as well as
incorporating the use of stories) will have on students’ conceptual change. This will reveal
not only its effect on achievement but the effect on conceptual change of the students.
APPENDIX A
Sample Responses (from four students)
Case I. A couple, Mr. and Mrs. Oliseh, had a child. At birth, the child had the
physical characteristic of a female, i.e., female genitalia. However, as the child grew,
she developed male characteristics. These included deep voice, flat chest, and no
ovulation or menstruation. What is the possible cause of this problem?
Student A: The cause is maybe she was cursed while in the womb or may be because of
poor nutrition and malnutrition.
Student B: In the world, many people do not like other people’s progress and because of
it, they might go to a native doctor and due to charm or any drug that the wicked person do
to the child, the child will turn to male so that she will be useless to the parents because no
man can marry a girl that is his fellow man.
Student C: I think it is from an enemy who went to the herbalist to charm the child.
Student D: I think that one insect called ogbakwulu nwoke ogbakwulu nwanyi (meaning
“converter to male” “converter to female”) stung her.
CASE II. Another couple, Dr. and Mrs. Uwaonu, not related to Mr. And Mrs. Oliseh,
also had a child. Their case seemed to be the opposite of the earlier case in that the
child had the physical characteristic of a male, i.e., male genitalia. As the child grew,
he developed female secondary characteristics, e.g., growth of the breast. What could
be the possible reason for this phenomenon?
Student A: It may be because she was placed under a curse by the wicked ones or that she
was in a cult and later decamped and the cult members made this happen to her child.
Student B: It may be a disease or due to one sickness and another that the child develops
the secondary characteristics of a female.
Student C: I think it is a problem of medical incompetence at birth.
Student D: I think that it is may be since the father is a doctor, he helped in aborting a male
child. It happened that the spirit of the male child did not rest and the result was that their
male child turned to a girl.
CASE III. Mr. and Mrs. Ede had five children and four of them died in infancy. What
likely reason could there be for this tragedy?
Student A: The likely reasons are poor nutrition or a curse on the family. They should seek
help from God or the doctor.
Science Education DOI 10.1002/sce
ADDRESSING NONSCIENTIFIC PRESUPPOSITIONS IN GENETICS
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Student B: Mr. Ede may be a sickle cell carrier and his wife may also be a carrier. If they
give birth to five children, four that died may be sicklers. Mr. and Mrs. Ede should seek
help from the doctor.
Student C: Those children as believed by my village are Ogbanje, who want to bring
suffering to their mother by dying and reincarnating up to four times and the fifth time
she/he decided to stay for sometime.
Student D: I think that the children are Ogbanje. Mr. and Mrs. Ede should seek help from
divine healer or a native doctor.
CASE IV. A couple, Mr. and Mrs Onyia, are both dark in complexion but have an
albino child. No known member of their family is an albino. Why should this occur?
Student A: It is likely the child inherited it from the grandparents or great grandparents.
Student B: The most likely reason is that the parents of the couple or maybe their
grandparents or their great grandparents or somewhere from earlier generations the couple
inherited the trait for albinism.
Student C: The most likely reason is that the woman would have slept with another man
who made her pregnant.
Student D: The most likely reason is that the womb of the mother is fair or white although
she is physically black.
∗
Note: Student D seems to be the student with the highest level of nonscientific presuppositions. The responses from this student should not be taken as atypical, but rather they
represent typical responses from the population from which the sample was
drawn.
APPENDIX B
Sample Questions From PI
Please select from the alternatives given the option that best represents in your opinion
the most likely cause of the phenomenon represented by the story.
1. A couple, Mr. and Mrs. Oliseh, had a child. At birth, the child had the physical characteristic of a female, i.e., female genitalia. However, as the child grew, she developed male
characteristics. These included deep voice, flat chest, and no ovulation or menstruation.
What is the possible cause of this problem?
(a) the problem is genetic in origin *(scientific)
(b) an insect ogbakwulu nwoke, ogbakwulu nwanyi stung her *(popular culture).
(c) the child is under a curse from either the gods or somebody *(spiritist)
2. Mr. and Mrs. Ede had five children and four of them died in infancy. What likely reason
could there be for this tragedy?
(a) It is the carelessness of the couple *(popular culture)
(b) The children are likely to be sicklers *(scientific)
(c) They belong to the ogbanje cult *(metaphysical/spiritist).
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MBAJIORGU ET AL.
3. A couple, Mr. and Mrs Onyia, are both dark in complexion but have an albino child. No
known member of their family is an albino. Why should this occur?
(a) The parents are carriers of the gene for albinism *(scientific)
(b) It is a punishment from the gods *(spiritist)
(c) The child is fathered by another man, other than Mr. Onyia *(popular culture)
*These categories were not included in the instrument as at the time of administration to
students.
APPENDIX C
Sample Questions From the Achievement Test on Genetics
1. The presence of an extra X chromosome (XXX) in a female will give rise to
(a) a male that looks like a female
(b) a normal but sterile female
(c) a female that fails to develop secondary sexual characteristics
(d) a mentally retarded fertile female
2. The presence of an extra X chromosome in a male (XXY) will result in
(a) a male that shows abnormal female sexual characteristics
(b) death in infancy
(c) Down syndrome
(d) a male that remains smallish even in very advanced age
3. Which of the statements is not correct about sex determination?
(a) females contribute half of the sex chromosomes
(b) males contribute X or Y chromosome
(c) females contribute only an X chromosome
(d) females alone determine the sex of the child
4. In human beings, the albino trait is recessive and the normal skin color is dominant.
Therefore the probability of parents that are carriers for albinism having an albino child is
(a) 1 /4
(b) 1 /2
(c) 1 /3
(d) 1
5. A man normal for the sickle cell trait (AA) married a woman homozygous recessive
for the trait (SS). They had a child who is a carrier for the sickle cell trait. Which of the
following genotypes could be associated with the child for the sickle cell trait?
(a) AO
(b) AS
(c) SS
(d) AA
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