Skip to main content
Log in

Reasoning about science-related uncertain issues and epistemological perspectives among children

  • Published:
Instructional Science Aims and scope Submit manuscript

Abstract

In order to fulfill social responsibility, one of the goals in science education is to equip students with the competence of scientific reasoning. Nevertheless, psychological studies have found that people in general do not have adequate ability to make scientific arguments in everyday situations. Later studies found that the inadequate ability was associated with the development of personal epistemology. However, the conclusion is drawn mostly from research with adults or adolescents. This study attempted to examine the relation between scientific reasoning in informal contexts and the epistemological perspectives demonstrated by elementary school pupils. Participants of the study were 62 sixth graders who were interviewed to criticize two science-related uncertain issues. Content analysis showed that most children had developed the absolutist form of personal epistemology. Chi-square analyses suggested that the more multiplist view toward the certainty of knowledge and the process of knowing, the better coordination of theory and evidence as well as reflective reasoning. In addition, children’s beliefs about the certainty of knowledge, source of knowledge and concept of justification were seemingly consistent across different issues. Nevertheless, content analysis showed that the criteria used to make judgments varied with problem contexts.

This is a preview of subscription content, log in via an institution to check access.

Access this article

Price excludes VAT (USA)
Tax calculation will be finalised during checkout.

Instant access to the full article PDF.

Fig. 1
Fig. 2
Fig. 3

Similar content being viewed by others

References

  • American Association for the Advancement of Science (AAAS). (1990). Science for all Americans. New York: Oxford University Press.

    Google Scholar 

  • Astington, J. W., Pelletier, J., & Homer, B. (2002). Theory of mind and epistemological development: The relation between children’s second-order false-belief understanding and their ability to reason about evidence. New Ideas in Psychology, 20, 131–144. doi:10.1016/S0732-118X(02)00005-3.

    Article  Google Scholar 

  • Baron, J. (1994). Thinking and deciding. NY: Cambridge University Press.

    Google Scholar 

  • Baxer Magolda, M. B. (1992). Knowing and reasoning in college: Gender-related patterns in students’ intellectual development. San Francisco: Jossey Bass.

    Google Scholar 

  • Brown, A. L. (1987). Metacognition, executive control, self-regulation, and other more mysterious mechanisms. In F. E. Weinert & R. H. Kluwe (Eds.), Metacognition, motivation, and understanding (pp. 65–116). Hillsdale, NJ: Lawrence Erlbaum Associates.

    Google Scholar 

  • Burr, J. E., & Hofer, B. K. (2002). Personal epistemology and theory of mind: Deciphering young children’s beliefs about knowledge and knowing. New Ideas in Psychology, 20, 199–224. doi:10.1016/S0732-118X(02)00010-7.

    Article  Google Scholar 

  • Chinn, C. A., & Brewer, W. F. (1998). An Empirical test of a taxonomy of responses to anomalous data in science. Journal of Research in Science Teaching, 35, 623–654. doi:10.1002/(SICI)1098-2736(199808)35:6<623::AID-TEA3>3.0.CO;2-O.

    Article  Google Scholar 

  • Collins, H., & Pinch, T. (1993). The golem: What everyone should know about science. Cambridge: Cambridge University Press.

    Google Scholar 

  • Driver, R., Newton, P., & Osborne, J. (2000). Establishing the norms of scientific argumentation in classrooms. Science Education, 84, 287–312. doi:10.1002/(SICI)1098-237X(200005)84:3<287::AID-SCE1>3.0.CO;2-A.

    Article  Google Scholar 

  • Duell, O. K., & Schommer-Aikins, M. (2001). Measures of people’s beliefs about knowledge and learning. Educational Psychology Review, 13, 419–449. doi:10.1023/A:1011969931594.

    Article  Google Scholar 

  • Duschl, R. A. (1990). Restructuring science education. NY: Teachers College Press.

    Google Scholar 

  • Duschl, R. A., & Osborne, J. (2002). Supporting and promoting argumentation discourse in science education. Studies in Science Education, 38, 39–72. doi:10.1080/03057260208560187.

    Article  Google Scholar 

  • Flavell, J. (1979). Metacognition and cognitive monitoring: A new area of cognitive-developmental inquiry. The American Psychologist, 34, 906–911. doi:10.1037/0003-066X.34.10.906.

    Article  Google Scholar 

  • Giere, R. N. (1988). Explaining science: A cognitive approach. Chicago: University of Chicago Press.

    Google Scholar 

  • Giere, R. N. (1991). Understanding scientific reasoning (3rd ed.). Forth Worth, TX: Holt, Rinehart & Winston.

  • Hofer, B. K. (2001). Personal epistemology research: Implications for learning and instruction. Educational Psychology Review, 12, 353–382. doi:10.1023/A:1011965830686.

    Article  Google Scholar 

  • Hofer, B. K., & Pintrich, P. R. (1997). The development of epistemological theories: Beliefs about knowledge and knowing and their relation to learning. Review of Educational Research, 67, 88–140.

    Google Scholar 

  • Hofer, B. K., & Pintrich, P. R. (Eds.). (2002). Personal epistemology: The psychology of beliefs about knowledge and knowing. NJ: Lawrence Erlbaum Associates.

    Google Scholar 

  • Hogan, K. (2000). Exploring a process view of students’ knowledge about the nature of science. Science Education, 84, 51–70. doi:10.1002/(SICI)1098-237X(200001)84:1<51::AID-SCE5>3.0.CO;2-H.

    Article  Google Scholar 

  • Johnson-Laird, P. N., & Byrne, M. J. (1991). Deduction. Hillsdale: Lawrence Erlbaum Associates.

    Google Scholar 

  • Johnson-Laird, P. N., & Shafir, E. (1994). Reasoning and decision making. Cambridge: Blackwell.

    Google Scholar 

  • Jonassen, D. H. (1996). Computers in the classroom: Mindtools for critical thinking. Englewood Cliffs, NJ: Prentice-Hall Inc.

    Google Scholar 

  • King, P., & Kitchener, K. S. (1993). The development of reflective thinking in the college years: The mixed results. New Directions for Higher Education, 84, 25–42.

    Google Scholar 

  • King, P., & Kitchener, K. (1994). Developing reflective judgment: Understanding and promoting intellectual growth and critical thinking in adolescents and adults. San Francisco: Jossey-Bass.

    Google Scholar 

  • Kitchener, K. S. (1983). Cognition, metacognition and epistemic cognition. Human Development, 26, 222–232.

    Article  Google Scholar 

  • Kitchener, K. S., Lynch, C. L., Fischer, K. W., & Wood, P. K. (1993). Developmental range of reflective judgment: The effect of contextual support and practice on developmental stage. Developmental Psychology, 29, 893–906. doi:10.1037/0012-1649.29.5.893.

    Article  Google Scholar 

  • Kolsto, S. D., Bungum, B., Arnesen, E., et al. (2006). Science students’ critical examination of scientific information related to socioscientific issues. Science Education, 90, 632–655. doi:10.1002/sce.20133.

    Article  Google Scholar 

  • Kortland, K. (1996). A STS case study about students’ decision making on the waste issue. Science Education, 80, 673–689. doi:10.1002/(SICI)1098-237X(199611)80:6<673::AID-SCE3>3.0.CO;2-G.

    Article  Google Scholar 

  • Kuhn, T. S. (1970). The structure of scientific revolution. Chicago: The University of Chicago Press.

    Google Scholar 

  • Kuhn, D. (1991). The skill of argument. Cambridge: Cambridge University Press.

    Google Scholar 

  • Kuhn, D. (1993). Science as argument: Implications for teaching and learning scientific thinking. Science Education, 77, 319–337. doi:10.1002/sce.3730770306.

    Article  Google Scholar 

  • Kuhn, D. (1999). A developmental model of critical thinking. Educational Researcher, 28, 16–26, 46.

    Google Scholar 

  • Kuhn, D., Amsel, E., & O’Loughlin, M. (1988). The development of scientific thinking skills. San Diego, CA: Academic.

    Google Scholar 

  • Kuhn, D., Cheney, R., & Weinstock, M. (2000) The development of epistemological understanding. Cognitive Development, 15, 309–328.

    Google Scholar 

  • Land, S. M., & Hannafin, M. J. (1996). A conceptual framework for the development of theories-in-action with open-ended learning environments. Educational Technology Research and Development, 45, 47–73.

    Article  Google Scholar 

  • Lawson, A. E., Clark, B., Cramer-Meldrum, E., Falconer, K. A., Sequist, J. M., & Kwon, Y.-J. (2000). Development of scientific reasoning in college biology: Do two levels of general hypothesis-testing skills exist? Journal of Research in Science Teaching, 37, 81–101. doi:10.1002/(SICI)1098-2736(200001)37:1<81::AID-TEA6>3.0.CO;2-I.

    Article  Google Scholar 

  • Le Compte, M. D., & Preissle, J. (1993). Ethnography and qualitative design in educational research. NY: Academic Press.

    Google Scholar 

  • Lee, K., & Homer, B. (1999). Children as folk psychologists: The developing understanding of mind. In A. Slater & D. Muir (Eds.), The Blackwell reader in developmental psychology (pp. 228–252). Malden, MA: Blackwell Publishers.

    Google Scholar 

  • Lehrer, R., & Schauble, L. (2006). Scientific thinking and science literacy. In W. Damon, R. Lerner, K. A. Renninger, & I. E. Sigel (Eds.), Handbook of child psychology, Vol. 4, 6th ed.: Child Psychology in Practice (pp. 153–196). Hobbken, NJ: Wiley.

    Google Scholar 

  • Louca, L., Elby, A., Hammer, D., & Kagey, T. (2004). Epistemological resources: Applying a new epistemological framework to science instruction. Educational Psychologist, 39, 57–68. doi:10.1207/s15326985ep3901_6.

    Article  Google Scholar 

  • Mansfield, A. F., & Clinchy, B. M. (2002). Toward the integration of objectivity and subjectivity: Epistemological development from 10 to 16. New Ideas in Psychology, 20, 225–262. doi:10.1016/S0732-118X(02)00008-9.

    Article  Google Scholar 

  • Mason, L., & Scirica, F. (2006). Predication of students’ argumentation skills about controversial topics by epistemological understanding. Learning and Instruction, 16, 492–509. doi:10.1016/j.learninstruc.2006.09.007.

    Article  Google Scholar 

  • Means, M. L., & Voss, J. F. (1996). Who reasons well? Two studies of informal reasoning of different grade, ability, and knowledge levels. Cognition and Instruction, 14, 139–178. doi:10.1207/s1532690xci1402_1.

    Article  Google Scholar 

  • Newton, P., Driver, R., & Osborne, J. (1999). The place of argumentation in the pedagogy of school science. International Journal of Science Education, 21, 553–576. doi:10.1080/095006999290570.

    Article  Google Scholar 

  • Olson, D., & Astington, J. (1993). Thinking about thinking: Learning how to take statements and hold beliefs. Educational Psychologist, 28, 7–23. doi:10.1207/s15326985ep2801_2.

    Article  Google Scholar 

  • Perkins, D. N. (1985a). Reasoning as imagination. Interchange, 16, 14–26. doi:10.1007/BF01187588.

    Article  Google Scholar 

  • Perkins, D. N. (1985b). Postprimary education has little impact on informal reasoning. Journal of Educational Psychology, 77, 562–571. doi:10.1037/0022-0663.77.5.562.

    Article  Google Scholar 

  • Perkins, D. N., Farady, M., & Bushey, B. (1991). Everyday reasoning and the roots of intelligence. In J. F. Voss, D. N. Perkins, & J. W. Segal (Eds.), Informal reasoning and education (pp. 3–16). Hillsdale, NJ: Lawrence Erlbaum Associates.

    Google Scholar 

  • Perry, W. G. (1999). Forms of intellectual and ethical development in the college years. San Francisco, CA: Jossey-Bass.

    Google Scholar 

  • Pintrich, P. R. (1999). Motivational beliefs as resources for and constraints on conceptual change. In W. Schnotz, S. Vosniadou, & M. Carretero (Eds.), New perspectives conceptual change (pp. 33–50). Amsterdam: Pergamon/Elsevier.

    Google Scholar 

  • Pithers, R. T. (2000). Critical thinking in education: A review. Educational Research, 42, 237–249. doi:10.1080/001318800440579.

    Article  Google Scholar 

  • Sandoval, W. A. (2005). Understanding students’ practical epistemologies and their influence on learning through inquiry. Science Education, 89, 634–656. doi:10.1002/sce.20065.

    Article  Google Scholar 

  • Schauble, L., Glaser, R., Raghavan, K., & Reiner, M. (1991). Causal models and experimentation strategies in scientific reasoning. Journal of the Learning Sciences, 1, 201–238. doi:10.1207/s15327809jls0102_3.

    Article  Google Scholar 

  • Schommer, M. (1990). Effects of beliefs about the nature of knowledge on comprehension. Journal of Educational Psychology, 82, 498–504. doi:10.1037/0022-0663.82.3.498.

    Article  Google Scholar 

  • Schommer, M. (1994). An emerging conceptualization of epistemological beliefs and their role in learning. In R. Garner & P. A. Alexaner (Eds.), Beliefs about text and instruction with text (pp. 25–40). NJ: Erlbaum.

    Google Scholar 

  • Schommer-Aikins, M. (1993). Epistemological development and academic performance among secondary students. Journal of Educational Psychology, 85, 406–411. doi:10.1037/0022-0663.85.3.406.

    Article  Google Scholar 

  • Schommer-Aikins, M. (2002). An evolving theoretical framework for an epistemological belief system. In B. K. Hofer & P. R. Pintrich (Eds.), Personal Epistemology: The Psychology of Beliefs about knowledge and knowing (pp. 103–108). NJ: Lawrence Erlbaum.

    Google Scholar 

  • Talaska, R. A. (Ed.). (1992). Critical reasoning in contemporary culture. NY: State University of New York Press.

    Google Scholar 

  • Toulmin, S. (1958). The Uses of Argument. Cambridge: Cambridge University Press.

    Google Scholar 

  • Tsai, C.-C. (1998). An analysis of scientific epistemological beliefs and learning orientations of Taiwanese eighth graders. Science Education, 82, 473–489. doi:10.1002/(SICI)1098-237X(199807)82:4<473::AID-SCE4>3.0.CO;2-8.

    Article  Google Scholar 

  • Tsai, C.-C. (1999). “Laboratory exercises help me memorize the scientific truths”: A study of eighth graders’ scientific epistemological views and learning in laboratory activities. Science Education, 83, 654–674. doi:10.1002/(SICI)1098-237X(199911)83:6<654::AID-SCE2>3.0.CO;2-Y.

    Article  Google Scholar 

  • Tsai, C.-C. (2000). Relationships between student scientific epistemological beliefs and perceptions of constructivist learning environments. Educational Research, 42, 193–205. doi:10.1080/001318800363836.

    Article  Google Scholar 

  • Tsai, C.-C. (2001). A review and discussion of epistemological commitments, metacognition, and critical thinking with suggestions on their enhancement in internet-assisted chemistry classrooms. Journal of Chemical Education, 78, 970–974.

    Google Scholar 

  • Tsai, C.-C. (2004). Beyond cognitive and metacognitive tool: The use of the internet as an “epistemological tool” for instruction. British Journal of Educational Technology, 35, 525–536. doi:10.1111/j.0007-1013.2004.00411.x.

    Article  Google Scholar 

  • Voss, J. F., Perkins, D. N., & Segal, J. W. (Eds.). (1991). Informal reasoning and education. Hillsdale, NJ: Lawrence Erlbaum Associates.

    Google Scholar 

  • Weinstock, M. P., Neuman, Y., & Glassner, A. (2006). Identification of informal reasoning fallacies as a function of epistemological level, grade level, and cognitive ability. Journal of Educational Psychology, 98, 327–341. doi:10.1037/0022-0663.89.2.327.

    Article  Google Scholar 

  • Wellman, H. M., Cross, D., & Watson, J. (2001). Meta-analysis of theory-of-mind development: The truth about false belief. Child Development, 72, 655–684. doi:10.1111/1467-8624.00304.

    Article  Google Scholar 

  • Willis, S., & Schaie, K. W. (1993). Everyday cognition: Taxonomic and methodological considerations. In J. M. Puckett & H. W. Reese (Eds.), Mechanisms of everyday cognition (pp. 33–53). Hillsdale, NJ: Lawrence Erlbaum Associates.

    Google Scholar 

  • Yang, F. Y. (2004). Exploring high school students’ use of theory and evidence in an everyday context: The role of scientific thinking in environmental science decision-making. International Journal of Science Education, 26, 1345–1364. doi:10.1080/0950069042000205404.

    Article  Google Scholar 

  • Yang, F. Y. (2005). Student views concerning evidence and the expert in reasoning a socio-scientific issue and personal epistemology. Educational Studies, 31, 65–84. doi:10.1080/0305569042000310976.

    Article  Google Scholar 

  • Yang, F. Y., & Anderson, O. R. (2003). Senior high school students’ preference and reasoning modes about nuclear energy use. International Journal of Science Education, 25, 221–244. doi:10.1080/09500690210126739.

    Article  Google Scholar 

  • Yang, F. Y., Chang, C. Y., & Hsu, Y. S. (2008). Teacher views about the constructivist instruction and personal epistemology—A national study in Taiwan. Educational Studies, 34, 527–542.

    Google Scholar 

  • Zeidler, D. L. (1997). The central role of fallacious thinking in science education. Science Educator, 7, 38–46.

    Google Scholar 

  • Zeidler, D. L., Sadler, T. D., Simmons, M. L., & Hower, E. V. (2005). Beyond STS: A research-based framework for socioscientific issues education. Science Education, 89, 357–377. doi:10.1002/sce.20048.

    Article  Google Scholar 

  • Zimmerman, C. (2000). The development of scientific thinking skills in elementary and middle school. Developmental Review, 20, 99–149. doi:10.1006/drev.1999.0497.

    Article  Google Scholar 

Download references

Acknowledgement

Funding of this research work is supported by National Science Council, under grants NSC 95-2511-S-001-MY3 and NSC 95-2511-S-003-026.

Author information

Authors and Affiliations

Authors

Corresponding author

Correspondence to Chin-Chung Tsai.

Appendices

Appendix A: the interview issues

Issue 1: earth quake prediction

News Reports: Report I: China Times: Focus Section II: 2003/09/26

There are a group of eel catfish that has been raised in the Miaoli Educational Sea Park (MESK). Recently, these eel catfishes became anxious, and about 10 eel catfishes died suddenly due to jumping out of the fish tank. It was observed that the event was seemingly relevant to the big earthquake just happened. No wonder, “earthquake fish” is another name for the eel catfish. Y. C. Chang, manager of MESK, stated that past experiences showed that this phenomenon could occur both before and after earthquakes, especially before earthquakes. Y. C. Chang mentioned that about 80 eel catfishes suddenly ran into one another, and 40 of them jumped out of the fish tank and died. The workers of the MESK felt puzzled toward this event, but no one knew the reason. The idea of “earthquake fish,” which is a predictor of earthquakes, popped up in the mind after the occurrence of a big earthquake the other day. In fact, eel catfishes have been behaving abnormally these days, such as moving out of the habitat, running into one another, and jumping out of the fish tank. Y. C. Chang affirmed the relationship between the abnormality of eel catfishes and earthquakes that happened in Taiwan these days.

Y. C. Chang pointed out that Japan is a country where earthquakes occur frequently, and their biologists have already put efforts on the research of catfish. The researchers observe catfishes, which are raised in the laboratory, everyday, and have found out that catfishes seem to become anxious a few days before the occurrence of earthquakes with magnitude <5. Y. C. Chang believes that the idea of “catfish” predicting earthquake can be applied in Taiwan, so that people can get sufficient time for prevention, which will lower the numbers of tragedy.

Report II: China Times: Tao Zhu Miao Section 4: 2004/02/18

In this early morning, an earthquake with magnitude of 8.0 took place in Hokkaido, Japan. Dr. Tian, an astronomer in Japan, had predicted that there would be a strong earthquake breaking out near Tokyo, Japan, so the issue of “earthquake prediction” was triggered. Dr. Tian used astronomical instruments to monitor the electronic waves in the sky before the happening of earthquakes. Dr. Yie, a researcher from Academia Sinica in Taiwan, pointed out that the astronomic method, which is scientifically based, is one of the ways used for predicting earthquakes. However, scholars and officers in the Earthquake Record Center at the Central Weather Bureau stated that Dr. Tian’s predication was actually a failure because of the wrong location he predicted.

Tian’s prediction of an earthquake with magnitude of 7.2 near Tokyo, Japan in September 15 or 16 did not come true. On the other hand, no researcher made any related prediction about this rare earthquake with magnitude of 8.0 occurring this early morning in Hokkaido. Dr. Yie said that earthquake prediction is the common goal for the earthquake researchers all over the world. However, the mechanisms of earthquake are extremely complicated. The rate of a successful prediction will still be low even 20 or 30 years later. Therefore, people should spend more time and put more efforts on the prevention of earthquake hazards.

Issue II: land subsidence

News Report: Residents disagree building wells (2002/05/06)

The water company has been preparing for building the 11th well in the Eastern area of a town named “Yuanlin” yesterday, but about 20 residents went to the scene for protesting this project. The director of the water company has communicated with the residents for about 2 h, but there was no common consensus at last. The residents argued that the location where the well is going to build is located upon an earthquake fault line. One doubted that the land subsidence occurring in the major earthquake 921 in 2000 was triggered by the digging of too many wells. In order to avoid the same tragedy, the residents will have to stop the water company’s project.

An excavator drove into the land in the morning for digging the well. When residents received this message, they ran to the scene and stopped the construction. Mr. Tseng, the director of the local police station, went to scene for controlling the quarrel. The residents complained that the land subsidence during earthquake 921 have caused the crash of about 100 houses. In this case, it is unreasonable for the water company to build another well. They hoped the water company could take their life safety into consideration. The residents said that in a small town like Yuanlin, there are already 10 wells. Now, the water company is going to building the 11th well, which has insulted them beyond the limit. Eastern Yuanlin is located right above a fault line which is thought to relate to the earthquake 921. Because of the well-known tragedy, residents are afraid of building more wells in the Eastern Yuanlin. The water company should think about people’s feeling when they plan to build another well.

Both sides communicated to each other for about 1 h under the sun, but there was no common consensus at last. The director of the water company tried to comfort the residents by stating that he had two lands in the Eastern Yuanlin, and he planned to contribute the lands for the well building. However, the residents thought that what the director said were useless. The director said, “the proposal of building wells has been examined and approved by related departments, so it will be safe.” Furthermore, he asked the residents to think about the large amount of water usage beforehand.

Appendix B: interview protocol

Questions

Purpose

Phase I: Prior to the reading of any news reports

1. Do you think the earthquake can be predicted?

Assessing participants’ prior beliefs/theories

2. Do you think scientists or experts have the same opinions, when considering the prediction issue? Why?

Assessing participants’ beliefs about the certainty of knowledge

3. When doing scientific researches (such as earthquake predication, life in Mars, global warming, etc.), do you think experts would reach an agreement eventually? Why?

Assessing participants’ beliefs in the certainty of knowledge

Phase II: Proceed to the reading of Issue I: Earthquake prediction

4. What is the difference between the two experiments?

Assessing participants’ prior understanding about the news report

5. Do you think now that the earthquakes can be predicted? Why?

Assessing participants’ beliefs about the process of knowing by examining reasons for change or keeping of prior beliefs

6. Which news do you believe more? Why?

Assessing participants’ beliefs about the process of knowing regarding the nature of experts and evidence, as well as criteria for judgment

7. What the experiment in which you do not believe can do more to make you believe? Please explain it.

Assessing participants’ performance on the coordination of theory and evidence, and their beliefs about experts and evidence (Process of knowing)

Phase III: Proceed to the reading of Issue II: Land subsidence

8. What was the cause for land subsiding reported in the news?

Assessing participants’ prior knowledge/theories about the event)

9. Do you think the protest by residents is reasonable? Why?

Assessing participants’ beliefs about the process of knowing regarding experts opinions and justification criteria

10. Are you sure about your ideas with respect to above questions? Why?

Assessing participants’ reflective reasoning

11. The water company claimed the safety of the well drilling. Do you believe their claim? Why?

Assessing participants beliefs about the process of knowing (views toward expert opinions versus evidence)

12. What do you think the water company should do to make the residents believe their claim? Please explain it.

Assessing participants’ performance on the coordination of theory and evidence, and their beliefs about experts and evidence (Process of knowing)

Rights and permissions

Reprints and permissions

About this article

Cite this article

Yang, FY., Tsai, CC. Reasoning about science-related uncertain issues and epistemological perspectives among children. Instr Sci 38, 325–354 (2010). https://doi.org/10.1007/s11251-008-9084-3

Download citation

  • Received:

  • Accepted:

  • Published:

  • Issue Date:

  • DOI: https://doi.org/10.1007/s11251-008-9084-3

Keywords

Navigation