Default Nudges vs Price Discounts in Teen Food Choices

ISEF Category: Behavioral and Social Sciences

Subcategory: Other  ·  Difficulty: Intermediate  ·  Setup: School Lab  ·  Time: 1 to 2 Months

The Hook

A tiny menu choice can change what people buy before they think about it. In a school store or cafeteria, that can shape what students eat every day. You can test whether a healthy default changes choices more than a price cut with the same expected value. That gives you a real behavior study, not just a guess.

What Is It?

A default option is the choice already set for you. Think of it like a form with one box already checked. In this project, the healthy side starts as the pre-selected choice, so students have to switch if they want something else.

A price discount works differently. It changes the cost of the healthy side, so students may pick it because it feels like a better deal. Your job is to compare those two forces, habit and price, and see which one changes behavior more in your school setting.

This project sits in behavioral economics, which studies how real people make choices, not just how they say they will. You are looking at decision making in a place students already know well, so the results can feel practical and easy to explain.

Why This Is a Good Topic

This is a strong science fair topic because you can measure real choices, change one thing at a time, and compare two clear interventions. It connects to student health, cafeteria design, and how schools can guide better eating without banning options. You can learn experimental design, data analysis, and basic statistics with a project that feels real and easy to understand.

Research Questions

• How does a pre-selected healthy side change the share of students who choose it compared with a regular menu setup?
• What is the effect of a price discount on the healthy side compared with no discount?
• Does a default nudge increase healthy-side choices more than a discount with similar expected value?
• To what extent do grade level or lunch period change how students respond to defaults versus discounts?
• Which intervention leads to fewer order reversals, the default option or the price discount?
• How does repeated exposure to the same choice setup affect student response over time?

Basic Materials

• Consent or school approval forms, if required by your district.
• Simple menu cards or order sheets with two versions of the choice setup.
• Tally sheet or spreadsheet for recording choices.
• Laptop or tablet for data entry.
• Calculator or spreadsheet software for basic analysis.
• Poster board or slide deck for presenting results.

Advanced Materials

• Digital point-of-sale export or coded order log from the school store or cafeteria.
• Randomization plan for assigning days or lunch periods to conditions.
• Survey tool for brief follow-up questions on choice reasons.
• Statistical software such as R or Python for regression analysis.
• Spreadsheet with student-level or group-level identifiers, coded to protect privacy.
• Background data on menu items, prices, and participation rates.

Software & Tools

• Google Sheets: Organizes order data, calculates percentages, and makes simple charts.
• R: Runs statistical tests and models that compare the two interventions.
• Python: Cleans records and plots choice patterns across days or lunch periods.
• jamovi: Offers free point-and-click statistics for students who want easier analysis.
• Google Forms: Collects short feedback on why students picked each option.

Experiment Steps

1. Define one outcome, such as whether a student chose the healthy side or not.
2. Choose two conditions that are fair to compare, a default nudge and a price discount.
3. Plan how you will assign conditions across days, lunch periods, or menu lines.
4. Set controls that keep the food options, signage, and placement as similar as possible.
5. Decide how you will record choices, check data quality, and protect privacy.
6. Plan the analysis that will compare the size of the effect in each condition.

Common Pitfalls

• Changing the menu items between conditions, which makes the nudge effect impossible to separate from food appeal.
• Using different signs or staff instructions on different days, which adds a hidden confound.
• Mixing student groups across conditions without a plan, which creates biased comparison groups.
• Recording only total sales, which hides whether the healthy side actually won more often.
• Forgetting to track day-to-day lunch traffic, which can make a busy day look like a stronger intervention than it really was.

What Makes This Competitive

A stronger project would go beyond a simple before-and-after count. You could randomize by lunch period, compare multiple grades, and test whether the effect holds after students see the setup more than once. Strong analysis matters too, especially if you estimate effect size, confidence intervals, and interaction effects instead of just reporting percentages. A clear design and careful controls can turn a simple cafeteria study into a serious behavior experiment.

Project Variations

• Test whether the same default versus discount effect appears for fruit cups instead of side dishes.
• Compare a pre-selected healthy side with a pre-selected healthy drink to see whether the category changes student response.
• Add a social cue, such as a message that most students chose the healthy side, and compare it with the default and discount conditions.

Learn More

• PubMed: Search for review articles on defaults, nudges, and food choice in adolescents.
• NIH: Look for plain-language summaries and funded research on behavioral interventions and health behavior.
• USDA Economic Research Service: Explore reports on school food choices, incentives, and pricing.
• Journal of Economic Behavior & Organization: Search for articles on choice architecture and consumer behavior.
• MIT OpenCourseWare: Use introductory materials on experimental design and statistics for planning your study.