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Hypothesis vs. Theory? Demo the Difference with a “Two-Legged Stool” Game

When Dr. Nicola Plowes heard students misuse key scientific terms, she headed for the craft supply store and made a game with powerful, repeatable results.


Nicola Plowes, PhD

Assistant Professor of Life Sciences, Mesa Community College, Mesa, AZ

PhD in Entomology, BS in Biology (Ecology, Evolution, Conservation)

When life sciences professor Nicola Plowes, PhD, first started teaching, she was a traditional lecturer: She approached each class with a set of PowerPoint slides, a pointer, and a prepared speech. Over time, however, she adjusted her approach.

“Some topics need more directed lecturing; others benefit from more hands-on, exploratory approaches,” she says. “At the introductory level, we need to construct a very clear foundation upon which students can build. Literally and figuratively.”

One such literal and figurative example is the “two-legged stool lesson” she employs in her 100-level Biology Concepts course at Mesa Community College in Arizona. Its purpose is to clear up students’ confusion over the words hypothesis, theory, and proof.

Plowes notes that this is more than quibbling over semantics. Science is looking for truth, and when sufficient scientific evidence supports a theory, you are looking at truth. “For example, someone says, ‘I don’t believe in climate change.’ In reality, what they’re saying is, ‘I don’t understand what climate change is,’” she says. “Because climate change exists whether you believe in it or not.”

While this example is helpful in explaining the distinction of a proof—a scientific fact—she finds that hypothesis and theory can be more troublesome to tease out. So she purchased some pipe cleaners and dice to offer students a more observable explanation.


“Allowing students to be creative helps them better understand the concept of scientific method. You are asking them to think about complex and multidimensional ideas, so encouraging their creative reactions is important.”

— Nicola Plowes, PhD

Course: BIO 100 Biology Concepts

Course description: Introductory course covering basic principles and concepts of biology. Methods of scientific inquiry and behavior of matter and energy in biological systems are explored.


See resources shared by Nicola Plowes, PhD

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The Two-Legged Stool: Setup and game play

Plowes has always liked the idea of using common, concrete materials and examples to bring theoretical concepts to life. She got the idea to adapt this two-legged stool activity after hearing about similar lessons from other scientists. Here is how she sets it up, runs it, and follows through after it is done.

Paint a mental picture

Before getting into the game, Plowes has students imagine or look at a picture of a stool: She tells them that each leg of the stool represents a hypothesis (a suggested explanation or reasoned prediction). The seat is a theory, which is supported by many legs (hypotheses). If there are enough good, strong legs (hypotheses), the seat (theory) will stand. Even if one hypothesis were to be tested and rejected, the stool will remain sound, as long as enough other legs remain.

Review actual theories

At this point, Plowes reminds her class of a number of well-known theories to help put the concept in perspective. These include evolutionary theory, gravitational theory, and cell theory. She also reviews the climate change example, which illustrates the importance of knowing a theory from a hypothesis.

Divide up students and materials

To start the game, Plowes assigns groups of three to five students, which will then compete in the activity.

Plowes provides the following supplies for the game for each group:

  • 100 (12″) pipe cleaners
  • 20 (1/4″ X 12″) wooden dowels
  • 2 (12″-square) pieces of hardboard
  • 1 die
Review the rules and objective—then play!

Plowes tells the groups that the objective is simple: The first team to build a stable, two-level structure (a theory) is the winner. Here is how the game works:

1. A student in each group tosses the die. (All groups do this simultaneously.)

  • If she rolls 1–5, then she REJECTS the hypothesis and takes a pipe cleaner.
  • If she rolls a 6, she ACCEPTS the hypothesis and takes a wooden dowel.
  • She then builds what she can. (This may be nothing. For example, if she has only two dowel “legs,” she will not be able to support the hardboard—thus the name of the game.)

2. All groups repeat step 1 until one group finally builds a “table” that is able to remain standing.

Why make the odds of getting a pipe cleaner (rejected hypotheses) greater than a dowel (accepted hypothesis)? Plowes says it is to reinforce how common hypotheses are and how rarely they are accepted.

Theory vs. Hypothesis: What's the Difference?

Students often mix up theory and hypothesis because of the relational nature of the two, Plowes says.

  • In science, a theory is a tested, well-substantiated, unifying explanation for a set of verified, proven factors.
  • A hypothesis is either a suggested explanation for an observable phenomenon or a reasoned prediction of a possible causal correlation among multiple phenomena.

Thus, a theory is always backed by evidence, while a hypothesis is only a suggested possible outcome. As such, a hypothesis is testable and falsifiable.

4 ways to reinforce the lesson

Plowes has adopted a number of best practices to help engage all students. Here are her top recommendations.

1. Allow discussion during the activity

Encourage students to ask questions and talk about what they are learning while the game is happening, says Plowes. For example, if they ask, “What does it mean in real life if you come up with many hypotheses that get rejected?” she can explain that this is beneficial because, if many similar hypotheses are rejected, scientists can rule out an entire line of inquiry.

2. Share from your own experiences

Plowes shares some of her own research work with students. “For example, I talk about my research with desert ants and navigation,” she says. “I learned that if you remove visual cues like the ability to see distant mountains, ants’ ability to navigate is compromised, thus supporting the hypothesis that distant landmarks are a key feature of their navigational toolbox.” Plowes loves to show students how passionate she is about her science projects, in part because she hopes her enthusiasm will be contagious.

3. Mix in familiar learning approaches

Plowes maintains some elements of classic lesson structure to make students feel comfortable in class. “We have transitioned from old-fashioned lectures to very cutting-edge approaches, but sometimes students feel a little lost without these traditional touch points,” she says. Some of the classic strategies she employs include reviewing course objectives, providing textbook definitions of terms, summarizing major points, and providing resources for students to refer to later. For example, she frequently suggests students check out this University of California at Berkeley website to learn more about misconceptions in science.

4. Be supportive of creative thought

“Allowing students to be creative helps them better understand the concept of scientific method,” says Plowes. “You are asking them to think about complex and multidimensional ideas, so encouraging their creative reactions is important.” An example is if students bundle pipe cleaners together to make a sturdy “leg” to support their hardboard. While they are rule-breaking according to the official game, we can ask how to extend the analogy. “As scientists, we sometimes forget that negative data (rejected hypotheses) are also data, and they can contribute to theory building.”

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