The Nature of Science

The various fields of science have their own special ways of knowing, but the essentials of the natural sciences should be defined for the purpose of planning appropriate assessments.

The natural sciences are characterized by organized explanations incorporating both theoretical and empirical elements. Scientists attempt to construct theories that encompass as much factual and conceptual knowledge, including laws and principles, as possible. The construction of theories is a process involving the consideration of factual evidence, insightful questioning, creativity, and imagination.

Atomic theory and evolution theory are good examples of modern scientific theories that are central to the sciences as ways of knowing. They are sources of new hypotheses and logical deductions that can be tested. As these theories are refined, they continue to stimulate new questions and hypotheses. As with other scientific theories, each time they come into play in experimental situations, they are again subject to testing and the possibility of refutation. Each success broadens their domain and increases their usefulness. Verification of theories does not ensure truth, but it does extend their usefulness in explaining natural phenomena.

Useful theories enable an individual to make predictions under a specified range of conditions. Scientific theories must be testable according to standards of evidence and logical argumentation set by the scientific community; they are central to the scientific way of knowing and guiding observation. When scientists observe natural phenomena, their observations are made within the context of existing scientific theories. Nonscientists holding different views may perceive the same phenomena, but, through their subjective belief systems, may arrive at different conclusions. History is replete with examples of misunderstandings and miscommunication that are based, at least in part, on the use of different rules of observation.

Science consists of both theoretical and experimental knowledge that is constructed by the creativity, knowledge, and world view of scientists. Experimentation plays an essential role in generating and verifying scientific information. New findings and results of scientific observation and experimentation accumulate, enlarging the base of present knowledge and laying the foundation for future learning. Usually, scientific knowledge is structured, forming a web of interrelated concepts, laws, and principles. Whereas sensory data are sometimes ephemeral, concepts are precisely formulated and are multiply connected to other concepts or sensory data within a theory. Concepts without factual content (sensory data) are empty, whereas sensory data without concepts are difficult to understand and open to misinterpretation.

None of the processes usually associated with science -- for example, observing, measuring, classifying, deducing, inferring -- is unique to science. However, in science, these processes are given meaning by the context of the subject matter under investigation. Hence, observations of a mealworm seemingly walking endlessly around the sides of a container have new meaning when mealworm anatomy, behavior, and physiology are understood. Likewise, the wiggly lines a physicist observes on a photographic negative taken of a cloud chamber remain wiggly lines to most observers, but they become important sensory data (facts) when the conditions under which the lines were produced are known. A goal of science education, therefore, is to help students recognize the difference between personal opinion and knowledge gained through scientific investigation and debate.

Although the scientific disciplines are alike in their reliance on evidence, use of logic, and organization of factual information into concepts and theories, they differ with respect to what constitutes evidence, specific methods of investigation, and degree of quantification. Yet "there are common understandings among [scientists] about what constitutes an investigation that is scientifically valid" (American Association for the Advancement of Science, 1989). This view of the nature of science has profound implications for assessment, as reflected in the criteria outlined in chapter three.

The Science Curriculum

Because a major purpose of NAEP is to illuminate education policy, assessment of student science learning must take into account the science curriculum. Hence, the 1996 and 2000 NAEP Science Assessment Framework is based on a consensus regarding desirable elements of science education against which student attainment is to be measured.

In developing the Framework, the planning committee reviewed key blue-ribbon reports, examined exemplary practices, studied local and state-based innovations in science curricula, reviewed science education literature, and noted innovations emerging in other countries. Recent reports by government agencies and professional societies (National Science Board, 1983; American Association for the Advancement of Science, 1989; National Science Teachers Association, 1989; National Research Council, 1990) express unanimity in their goals for science education. For example:

• Students should acquire a core of scientific understanding, including organized factual information.

• Students should acquire the ability to relate scientific concepts to one another and to problems the students encounter in and out of school.

• Students should be able to apply science knowledge in practical ways.

• Students should be familiar with experimental design and have the ability to carry out scientific experiments that are developmentally appropriate.

• Students should acquire the science knowledge and understanding that will allow them the opportunity to pursue further study in scientific fields or enter science- or technology-related careers.

• Reduction of the traditional breadth of coverage in favor of greater depth, especially in high school science.

• Emphasis on development of such thinking processes as organizing factual knowledge around major concepts, defining and solving problems, accessing information and reasoning with it, and communicating with others about one's science results and understandings.

• Multidisciplinary and interdisciplinary approaches to science teaching.

• Approaches that encourage active student involvement and participation, such as participating in hands-on science activities; learning in small, cooperative groups; reflecting orally and in writing upon experiences; and completing sustained projects.

• Increased participation of underrepresented populations in challenging school science.

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