Walnuts and adolescent development: Experimental design practice

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Omega-3 fatty acids are important for brain health (Barnes et al., 2021; Lange, 2020; Thomas et al., 2021). Nuts—particularly walnuts—are high in omega-3 fatty acids (The Nutrition Source, n.d.).

After covering experimental design or as a experimental design booster in the lifespan chapter, give students this hypothesis, and then ask them to work in small groups to design an experiment that would test it.

Hypothesis: Eating walnuts will enhance the neuropsychological and behavioral development of adolescents.

Ask the groups to identify the independent variable—both experimental and control conditions—and the dependent variables. Students should also provide operational definitions of all variables. Before deciding on operational definitions, encourage students to consider what information they may be lacking. For example, has previous research revealed how many grams of walnuts a day may be needed? How many days or weeks may the walnuts need to be eaten to see any effects? What kinds of dependent measures might reveal effects? This is a good opportunity to explain the importance of a lit review. Knowing what other researchers have done and have discovered can inform how we design our study.

After groups have had an opportunity to design their studies, invite a representative from each group to share their design.

As an out-of-class assignment, ask students to read this freely available Lancet article on an experiment conducted in a dozen high schools in Barcelona (Pinar-Martí et al., 2023) and to answer these questions:

What was the independent variable? Identify both the experimental and control conditions. What was the operational definition used for the experimental condition?

What were the dependent variables? Hint: there were four neuropsychological variables and two behavioral variables.

When the researchers removed from their data analysis those in the experimental group who did not eat the amount of walnuts as requested, what results did they find?



Barnes, S., Chowdhury, S., Gatto, N. M., Fraser, G. E., & Lee, G. J. (2021). Omega‐3 fatty acids are associated with blood–brain barrier integrity in a healthy aging population. Brain and Behavior, 11(8), e2273. https://doi.org/10.1002/brb3.2273

Lange, K. W. (2020). Omega-3 fatty acids and mental health. Global Health Journal, 4(1), 18–30. https://doi.org/10.1016/j.glohj.2020.01.004

Pinar-Martí, A., Gignac, F., Fernández-Barrés, S., Romaguera, D., Sala-Vila, A., Lázaro, I., Ranzani, O. T., Persavento, C., Delgado, A., Carol, A., Torrent, J., Gonzalez, J., Roso, E., Barrera-Gómez, J., López-Vicente, M., Boucher, O., Nieuwenhuijsen, M., Turner, M. C., Burgaleta, M., … Julvez, J. (2023). Effect of walnut consumption on neuropsychological development in healthy adolescents: A multi-school randomised controlled trial. EClinicalMedicine, 59, 101954. https://doi.org/10.1016/j.eclinm.2023.101954

The Nutrition Source. (n.d.). Omega-3 fatty acids: An essential contribution. Harvard School of Public Health. Retrieved August 10, 2023, from https://www.hsph.harvard.edu/nutritionsource/what-should-you-eat/fats-and-cholesterol/types-of-fat/o...

Thomas, A., Baillet, M., Proust‐Lima, C., Féart, C., Foubert‐Samier, A., Helmer, C., Catheline, G., & Samieri, C. (2021). Blood polyunsaturated omega‐3 fatty acids, brain atrophy, cognitive decline, and dementia risk. Alzheimer’s & Dementia, 17(3), 407–416. https://doi.org/10.1002/alz.12195


About the Author
Sue Frantz has taught psychology since 1992. She has served on several APA boards and committees, and was proud to serve the members of the Society for the Teaching of Psychology as their 2018 president. In 2013, she was the inaugural recipient of the APA award for Excellence in the Scholarship of Teaching and Learning at a Two-Year College or Campus. She received in 2016 the highest award for the teaching of psychology--the Charles L. Brewer Distinguished Teaching of Psychology Award. She presents nationally and internationally on the topics of educational technology and the pedagogy of psychology. She is co-author with Doug Bernstein and Steve Chew of Teaching Psychology: A Step-by-Step Guide, 3rd ed. and is co-author with Charles Stangor on Introduction to Psychology, 4.0.