Resources: Course Assignments

Assignment: Perception and Food

Applications of the Delbouef Illusion

Which circle below looks bigger?

Two black circles are shown. The circle on the left has another black ring around the circumference of the circle, while the circle on the right does not.

Having already learned about the Ebbinghaus illusion, you were probably right in guessing that the circle with the ring around it appears larger than the non-surrounded circle. This is an example of the Delboeuf illusion, first identified by Belgian philosopher and mathematician Joseph Delbouef in 1887 or 1888. Modern psychologists have tested this illusion in various experiments, including one to determine if eyeshadow makes eyes look bigger (it does), and others to determine if the quantity of food on a plate looks larger if the plate is smaller.

Studies by Koert Van Ittersum and Brian Wansink[1] at the Cornell Food and Brand Lab have studied the effect of the Delbouef illusion on eating and serving behavior. In several different experiments, they measured if people would take more or less than a typical serving size depending on the size of their plate, the color of the plate, the color of the tablecloth, and how much they knew about the Delboeuf illusion.


Your mom is in charge of providing meals at the upcoming family reunion and she is worried about not having enough linguini alfredo (a white pasta) to serve the entire crew. She wants to ensure that no one takes too much food.

STEP 1: Read through the study, “Plate Size and Color Suggestibility: The Delboeuf illusion’s bias on eating and serving behavior” by Koert Van Ittersum and Brian Wansink. You can find the full article by searching online or using your library’s database.

STEP 2: Give your mom some advice on what size plates she should use, what color they should be, and what color tablecloths she should buy. Read through the study, then explain in a few paragraphs (between 200-400 words) how your mom can utilize of the Delboeuf illusion to minimize her costs at the reunion. Cite specific pieces of evidence (at least four quantitative examples) from the research.

Criteria Ratings Points
Presents a coherent summary of between 200-400 words Clearly writes a few explanatory paragraphs that demonstrate an understanding of the Delboeuf illusion Writing contains many errors or does not demonstrate an understanding of the Delboeuf illusion Writing is unclear and/or does not demonstrate an understanding of the Delboeuf illusion __/5
Recommendations Recommends the correct plate size, color of plate, and color of tablecloths according to the study Makes incorrect recommendations for either the correct plate size, color, or tablecloths Does not make, or incorrectly makes recommendations for the plate size, color, and tablecloths __/10
Evidence from research Includes at least four quantitative examples from the research Includes less than four quantitative examples from the research Does not include quantitative examples from the research __/5
Total: __/20
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  1. Research by Brian Wansink has been called into question following some significant errors and deceptive results presented in his publications. Since 2017, 17 of his papers were retracted and 15 were revised after it came to light that some of the data had been manipulated.


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