Exploring the Challenges and Opportunities of Theory-Laden Observation and Subjectivity: A Key NOS Notion

Abstract

One key NOS aspect often recommended for inclusion in school science programs is the issue of subjectivity and bias (sometime called theory-laden observations) when viewing the world. Everyone has some expectations or prior “theories” when making observations and students should have opportunities to explore this notion and understand the role of theory-laden observations in science. The purpose of this chapter is to help teachers understand this issue both with discussion of the issue and an example. First, we explore the idea of subjectivity related to the way in which all humans—scientists included—engage in observing. In many cases, what observers expect to see can be helpful in allowing the observer to ignore things that are not important. In other cases, when observers expect to see something, they do. Second, this chapter reports the results of an experiment in which observers expected to see the heart of a tiny aquatic crustacean—daphnia—speed up or slow down when exposed to chemicals such as nicotine or alcohol. This experiment demonstrated the expectancy effect because, although students reported the anticipated results, there were no active chemicals involved but students believed that alcohol or nicotine was introduced to the daphnia.

A.Appendices

1.1 Appendix A: The Use of Optical Illusions to Illustrate “Theory-Based” Observations

To illustrate the challenges inherent in “theory-based” observation, instructors may find it useful to secure a wide variety of optical illusions, particularly ones where two images are cleverly blended together in what are sometimes called ambiguous figures. One of these (Fig. 7.1) is the classic often referred to as Young Woman/Old Woman or My Wife and My Mother in Law. The origin of this figure is itself somewhat ambiguous with reports that it first appeared in a different form as a nineteenth century German postcard and was then redrawn by illustrator William Hill and published in the magazine Puck. Therefore, it seems reasonable to cite this as Hill (1915).

Fig. 7.1

Hill (1915). The classic My Wife and My Mother-in-Law ambiguous figure

For those who have not explored this image previously you will have no expectation. Some may first see a young woman who seems to be turning her face to the right. She is wearing a necklace and has a feather on her headscarf. It is just possible to see her left ear and chin, a bit of her left eyelash and her nose. With another look, the image may transform into an older woman who is turning her head somewhat to the left. The necklace of the young woman is now the woman’s mouth, the girl’s chin is now the nose of the older woman and what was previous the left ear becomes the older woman’s eye. They both share a while billowy headscarf, feather, and black hair.

To introduce the topic of “theory-based” observation to students not previously familiar with this image, a teacher could hand out cards to half the students saying, “Do you See the Old Woman in this Image?” and cards to the other half saying, “Do you See the Young Woman in this Image?” and then project the image to the entire class. Then ask the students to raise their hand if they see the Young Woman (or Old Woman, it doesn’t matter) and note which hands are raised. Certainly, there will be some who see the “wrong” image, have already seen this picture or can’t see either.

Generally, students who were “clued” by the statement on the card to look for the Old Woman will see that image most easily and vice versa. Having a range of such images and related optical illusions ready to share with the class along with two sets of cards directing students to look for different aspects of those images will provide some useful case material to engage students in a discussion of the role of prior expectations in observation. Fortunately, there are many such images available online for use in this fashion.

1.2 Appendix B: A Practical Example of Expectancy in Chemistry Class

In a series of lessons in chemistry class students explored some of the variables that affect the rate of gas production during electrolysis. One variable they noted was that the process occurs more quickly as the concentration of the electrolyte increased.

Next, I used this now-prior knowledge to reinforce the technique of electrolysis while introducing some of the problems of observation and thus discuss an important NOS element along with the traditional chemistry content. To extend this lesson and incorporate the expectancy effect, a bit of deceit was necessary.

I made a solution of sodium carbonate and poured that into three different containers. Each container was labeled a different concentration when in fact they were all the equal. I performed a demonstration for the students using a standard electrolysis set-up. I performed the demonstration three times, each with a supposedly different electrolyte solution and asked students to write down their observations. I mentioned the supposed concentration of electrolyte each time I did the demonstration and asked students simply to note anything of interest. They could have noted the time involved and the volume of gas produced if interested or simply watched from a qualitative perspective.

Students in each said things like “Oh wow look at how fast it’s going now!” However, the process was going at the same speed every time because the electrolyte concentration was identical in all three trials.

They knew from previous experiments that as the concentration of the electrolyte is increased the electrolysis rate also increases; so many students “saw” what they expected to see. Their expectations caused them to perceive an increase in reaction rate. Had they measured the amount of gas produced and noted the time involved they would have seen that all three trials produced the same amount of gas per unit time.

After the demonstration we had a conversation about the challenges of observation and the expectancy effect. Many of the students were amused that this could happen to them. Although I did hear one student remark, “I didn’t think anything special was happening, but everyone was saying it was, so I kept my opinion to myself.”

• Contributed by Kent Woodard, Chemistry Teacher.

• Rogers Arkansas Public Schools.