Thai pre-service science teachers' conceptions of the nature of science

Most pre-service science teachers hold mixed views about the NOS. Some of them are traditional, naïve, or uninformed, while others are contemporary or informed. The studies related to conceptions of the NOS held by pre-service science teachers can be categorised in four major groups: scientific knowledge, scientific method, scientists’ work, and scientific enterprise.

Scientific knowledge: Hypotheses, theories and laws

Regarding the relationship between hypotheses and theories, nearly half of the pre-service teachers surveyed in Thye and Kwen (2003) believed that a “scientific theory is a hypothesis that has not been proven yet” (p. 6). After being empirically tested, nearly all pre-service teachers stated that a hypothesis becomes a theory (Haidar, 1999).

Laws are statements or descriptions of discernible patterns developed to account for observable phenomena, while theories are inferred explanations for those phenomena. These two types of knowledge play different roles in science. However, many pre-service science teachers cannot distinguish between them. The most popular uninformed view about theories and laws for most of them is the “laws-are-mature-theories-fable” (Thye & Kwen, 2003). That is, many pre-service teachers believe that when enough supporting evidence is accumulated, theories become laws (Abd-El-Khalick, Bell, & Lederman, 1998). The common subsequent effect of the “laws-are-mature-theories-fable” is the misbelief that laws are less tentative than theories (Bell, Lederman, & Abd-El-Khalick, 2000).

Some prospective science teachers strongly believe in a simplistic hierarchical relationship between hypotheses, theories, and laws. For example, 73.1% of pre-service science teachers in Rubba and Harknes study (1993) had naïve conceptions that, “a hypothesis is tested by experiments. If it proves to be correct, it becomes a theory. After the theory has been proven many times by different people and has been around a long time, it becomes a law” (p. 418). It also leads to the favourite assertion about the credibility of hypotheses, theories, and laws, i.e., “theories are general propositions which are more credible than hypotheses but less credible than laws” (Ogunniyi, 1982, p. 28).

Scientific knowledge: Tentativeness of science

Regarding the status of scientific knowledge, we can categorise pre-service science teachers into two groups using a static-dynamic split. The pre-service teachers in the first group view science as stable or having static status (Craven, Hand, & Prain, 2002; Murcia & Schibeci, 1999; Tairab, 2001), while those in the second group view science as tentative or having a dynamic status (Bell et al., 2000; Mellado, 1997; Palmquist & Finley, 1997). In the static-science group, student teachers claimed that science is a collection of facts or a body of knowledge that explains the world with little or no elaboration. The purpose of scientific research, therefore, is to collect as much data as possible (Craven et al., 2002; Tairab, 2001). The student teachers belonging to this group appeared to have minimal awareness of the tentative nature of scientific knowledge (Murcia & Schibeci, 1999). In the dynamic-science group, the student teachers generally viewed subjectivity and creativity as the important factors contributing to the tentative nature of science (Abd-El-Khalick et al., 1998).

Scientific knowledge: Cumulative knowledge

The belief of scientific knowledge as cumulative knowledge is commonly held by pre-service teachers. In Haidar’s (1999) study, 48% of pre-service science teachers believed that scientific knowledge is cumulative and its advancement strongly depends on increasing observation.

Scientific knowledge: Scientific model

Many pre-service science teachers, especially those who hold the constructivist view, can articulate the role of scientific models as representations, rather than exact replicas, of experienced phenomena (Bell et al., 2000). A scientific model, for them, is seen not as a copy of reality, but as scientists’ best ideas or educated guesses to represent reality (Haidar, 1999). However, the appearance of scientific models in various public media, especially science textbooks, persuades most prospective science teachers to think about scientific models as a copy of reality. For example, in Thye and Kwen’s research (2003), 42% of pre-service teachers were not aware of the limitations of the scientific model. They asserted that, “since they [scientists] can provide the structure of atom universally in textbooks and reference books, I think that they must be very certain of it. Maybe they look at a microscopic view” (p. 6). In addition, 70% of prospective teachers in Ogunniyi’s study (1982) firmly believed that molecules, atoms, and electrons are empirical concepts. The example of the atomic model is frequently raised to support the conception of the scientific model as a copy of reality.

Scientific method: Universal, step-wise method

The scientific method is commonly perceived by pre-service science teachers as “a universally applicable, lock-step procedure” (Craven et al., 2002, p. 791). The percentage of pre-service science teachers who believe in a universal, step-wise scientific method varies from study to study, for example 23.5% (Murcia & Schibeci, 1999), to 33% (Craven et al., 2002), to 60% (Palmquist & Finley, 1997), to 65% (Haidar, 1999), and even to 100% (Mellado, 1997) of respondents. The main argument supporting a universal, step-wise scientific method is that its ordered, rigid stages lead to objectivity of scientific work and, finally, valid scientific claims (Mellado, 1997; Palmquist & Finley, 1997). Accordingly, the best scientists are defined as those who follow the steps of the scientific method (Haidar, 1999). Some pre-service teachers, however, did not believe in a universal step-wise scientific method (Mellado, 1997). They did not believe that “there are fixed steps that scientists always follow to lead them without fail to scientific knowledge” (Murcia & Schibeci, 1999, p. 1134).

Scientific method: Experiment

Some pre-service teachers raised experimentation as a necessary means to claim the validity of scientific knowledge. Thye and Kwen (2003) found that 79% of pre-service teachers expressed an uninformed view about scientific knowledge as experimental knowledge. They argued that “experiments are necessary to confirm truth and validity of scientific theory and inquiry. Without experimental validity, there is no scientific knowledge. There is only blind faith" (p. 5).

Scientists’ work: Theory-laden observation and subjectivity

Some of the most common bipolar views of the NOS are subjectivity and objectivity, theory-laden and theory-free, or value-laden and value-free. For most student teachers, subjectivity plays a major role in the development of scientific ideas (Palmquist & Finley, 1997). Subjectivity, which involves the individuality of scientists, e.g., their personalities, background, motivations, and beliefs, can affect scientists in selecting, interpreting, recording, and reporting evidence (Abd-El-Khalick et al., 1998; Murcia & Schibeci, 1999) and, eventually, generating conclusions or theories (Abd-El-Khalick et al., 1998; Thye & Kwen, 2003). For example, 46% of pre-service teachers in Thye and Kwen’s research (2003) believed that “the same piece of evidence or the same set of data can be subject to multiple interpretations" (p. 7).

However, many pre-service teachers strongly believed in objectivity in science, which is firmly based upon theory-free or value-free observation. For example, 40% of pre-service elementary teachers claimed that the validity of scientific knowledge originates from objective and value-free observation (Murcia & Schibeci, 1999). That is, scientists must be objective in their work (Palmquist & Finley, 1997), and observation should not be influenced by the theories they hold (Haidar, 1999). Objectivity is consequently proposed as one of the desirable characteristics of scientists. One of the four case studies in Mellado’s (1997) study, Ana, said that, “universal, objective criteria to exist, although extrascientific factors are at time involved…thence arriving at theories which are a true reflection of reality” (p. 343).

Scientists’ work: Creativity and imagination in science

The role of creativity and imagination in the construction of scientific ideas is acknowledged by most pre-service science teachers (Abd-El-Khalick et al., 1998; Bell et al., 2000). Creativity and imagination are thought to be mainly involved in designing research or experimental procedures, generating new ideas, and developing technology (Murcia & Schibeci, 1999). Creativity-related science leads most student teachers to “dismiss the view of science as a completely objective and rational activity” (Bell et al., 2000, p. 570). However, some pre-service teachers deny the role of creativity and imagination in science. In Murcia and Schibeci (1999), nearly 10% of pre-service teachers expressed the belief that, “science was fact or truth and creativity did not have a place” (p. 1132). Also, in Thye and Kwen (2003), 33% of pre-service teachers did not seem to think that creativity and imagination were required as steps of scientific investigation. A few of them adamantly stated that “there must not be any interpretation of the facts, they should speak for themselves” (p. 7).

Scientific enterprise: Social and cultural influences on science

The social and cultural influences on scientific enterprise are explicitly recognised by most pre-service science teachers (Haidar, 1999; Mellado, 1997; Murcia & Schibeci, 1999; Rubba & Harkness, 1993; Tairab, 2001). The literature revealed two types of cultural influences. The first comes from the larger society, while the other comes from the culture of science itself, including the influences of professional organisations, funding sources and peer review (Bell et al., 2000, p. 570). Research funding is seen as an important factor. In one study, 75.5% of pre-service elementary teachers believed that “the bodies [government departments] that supply the money for research influence the direction of science” (Murcia & Schibeci, 1999, p. 1135). However, the influences of social and cultural factors on scientific practice are sometimes overlooked by pre-service teachers (Abd-El-Khalick et al., 1998). Many of them neglected science as a social enterprise or a form of human cultural activity (Tairab, 2001).

Scientific Enterprise: Interaction between science and technology

It is, maybe, an easy task for pre-service teachers to recognise the interaction between science and technology, such as the ideas that science is the knowledge base for technology and technology influences scientific advancement (Rubba & Harkness, 1993). However, distinguishing between science and technology is probably a very difficult task for them (Rubba & Harkness, 1993). The commonplace naïve conception about science and technology is that technology is applied science (Tairab, 2001).