Concepts Across the Sciences: Cause and Effect

This post is by Jacqueline Katz, the 2022-2023 Albert Einstein Distinguished Educator Fellow at the Library of Congress.

Cause and effect relationships can be found in all disciplines of science. Students are regularly asked to manipulate independent variables (cause) and measure the effect on dependent variables to better understand their world. However, both inside and outside of the classroom, students sometimes incorrectly identify causal relationships because they don’t evaluate the available evidence.

Help students see the need to evaluate the evidence for cause and effect relationships by observing this Works Progress Administration (WPA) poster. After giving students time to observe the poster, ask:

• What message is this poster promoting?
• Who might be the intended audience for this poster?
• What cause and effect relationships are on the poster?

Discussing these questions will likely lead students to recognize that the poster promotes the idea that milk causes good teeth, vitality, endurance and strong bones. Ask students what they might need to assess the validity of these cause and effect relationships. Depending on when you do this during the school year, students will likely recognize that evidence from experimentation or research is required to assess the validity of these relationships.

Primary sources that were created around the time of this poster, 1940, offer evidence that was available to the creators. Divide the class into groups and provide each group with a primary source containing evidence. Two possible sources include: “Some Facts about Milk” (1938) and an image of rats undergoing a nutritional experiment(1942). Many more can be found by searching the Chronicling America database: Restrict your search to the years 1930-1940 using search terms like “milk” and “dairy.”

As groups are assessing the evidence, you may give them a framework of questions to consider:

• What were the experimental methods that resulted in this evidence?
• What might be missing from the evidence presented?
• Who was responsible for collecting and reporting the evidence?

When responding to the first question, students will likely determine that no controlled experimentation was conducted to connect milk to any of the variables listed on the WPA poster. In a unit on the scientific process, students might design an experiment that would provide evidence to support causation. Students will likely recognize the challenge this presents and might discuss correlation vs. causation.

To connect this primary source to class content, consider how “food value” relates to the current day calorie. This conversation could fit nicely into a biology unit on metabolism or a chemistry unit on energy. Students could work to verify some of the data included in the “Some Facts about Milk” article by conducting calorimetry in class.

A similar process of analysis can be employed by observing other WPA posters promoting cause and effect relationships. One interesting option could be this poster that connects poor posture and tuberculosis. Analyzing primary sources such as these WPA posters provides students the opportunity to strengthen their critical analysis of cause and effect relationships while furthering their content knowledge and media literacy.

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