To develop an understanding of why scientific investigations may yield varying results.
When people know how scientists go about their work and reach scientific conclusions, and what the limitations of such conclusions are, they are more likely to react thoughtfully to scientific claims and less likely to reject them out of hand or accept them uncritically. "Although most students believe that scientific knowledge changes, they typically think changes occur mainly in facts and mostly through the invention of improved technology for observation and measurement. They do not recognize that changed theories sometimes suggest new observations or reinterpretation of previous observations." (Benchmarks for Science Literacy, p.332)
This lesson gives students the opportunity to examine the nature of scientific research in the context of research pertaining to myopia, or nearsightedness. Myopia is a very common condition that affects between 30 and 40 percent of the U.S. population; it normally first occurs in school-age children. Since the eye continues to grow during childhood, nearsightedness generally develops before age 20. Thus, the subject of myopia should be of interest to most school children since they are likely to know someone with the condition.
Myopia also provides an interesting context in which to examine the scientific world view because though it is a very common condition, it is a topic about which there is still some scientific debate. A large body of scientific evidence supports the theory that myopia is hereditary. There is also evidence that nearsightedness may be caused by the stress of too much close vision work.
As directed on the Nearsightedness student esheet, students should listen to Reading Glasses, one of the Science Updates featured on Science NetLinks. This 90-second audio feature looks at the reason behind the almost universal increase in farsightedness among older people. This Science Update provides an interesting lead-in to the topic of vision problems and the research that scientists have conducted in this area.
After listening to the transcript, ask students:
- What are the researchers studying in this story?
- Why do some people need to wear reading glasses?
- Have you heard other explanantions for why people need glasses?
- Does far-sightedness occur only in older people? Why is it more prevalent in older people?
Begin this part of the lesson by telling students that they will look at research on a common vision problem: myopia, or nearsightedness. They specifically will look at nearsightedness in children.
To begin, ask students:
- What is myopia, or nearsightedness?
- Based on what you've learned about the cause of farsightedness, what do you think might be the cause of nearsightedness?
- Do you know anyone who is nearsighted?
- How old is this person?
- What does someone who is nearsighted see when they look around the classroom, or out the window?
- Would this individual also need glasses for reading? What would they need glasses for?
Have students view the images on the Nearsightedness student esheet. The photos illustrate what a person with normal vision sees compared to what a person with myopia, or nearsightedness, would see. Then have students continue with the esheet, reading the article from the Oregon Eye Center on refractive errors (this includes a detailed description of myopia).
The point of reading the article is to provide context for the heart of the lesson, which will deal with scientific inquiry. Therefore, don't focus too much attention on the science of myopia. It would be sufficient at this point for students to develop an understanding of myopia as a condition that occurs if your eye does not properly focus, or refract, light to the back of the eye.
Talk about ways of correcting vision problems. These might include glasses, contact lessons, and even corrective laser surgery. Tell students that all of these methods of correcting vision problems were developed through scientific investigations. Before the medical community put any of these methods into practice, researchers published their findings and invited others to validate or confirm their work.
Next, have students continue following instructions on the esheet, reading the article Why do scientists publish the results of their work in scientific journals? from the MadSci Network.
Then have students briefly discuss the following: "What do you think happens if other scientists repeat a published experiment and get different results?"
Tell students that an exploration of research on nearsightedness presents an opportunity to look at studies that have yielded different results.
Distribute the Nearsightedness In Children student sheet. Inform students that they will read about two studies on the causes of myopia and draw some conclusions about what happens when scientific studies yield results that don't agree. This activity can be done as a homework assignment.
After students have completed the assignment, ask students to share their answers to these questions:
- Describe the main differences in the procedures used by the researchers in Pennsylvania and the researchers in Ohio and Boston. For example, how many subjects were involved in each study? Did they ask the same questions?
- Would you describe the differences in the findings as significant or insignificant? Explain your answer.
- What do you think should happen now? Do you think that three studies are enough to definitely answer the question of whether or not night lights before the age of two contribute to nearsightedness in children? Why, or why not?
Use the Understanding What You Learned section of the student esheet to assess student understanding and summarize the ideas of this lesson.
The following Internet resources can be used to further explore the topics of myopia and vision:
- Eye Conditions, Disorders, and Treatments
- Your Eyes contains a Shockwave resource that demonstrates how the eye works.
For students who want to learn more about vision from a different perspective, the can go to How Bees See Their World from GEARS.