Plate Size, Color Can Lead People to Over-serve Food

With the holiday season upon us – and all the festive food it brings – people should know that the color contrast between dinnerware and what's placed on top can affect how much we serve ourselves and consume, according a Georgia Tech College of Management researcher.

Koert van Ittersum, an associate professor of marketing at Georgia Tech, descibes his research published in the Journal of Consumer Research, that sheds light on why people tend to over-serve themselves when given larger plates and bowls.

"Instead of scooping vanilla ice cream into a white bowl, you'd do better by your diet to pick a different color dish," explains Koert van Ittersum, an associate professor of marketing at Georgia Tech, who conducted this research with marketing professor Brian Wansink of Cornell University.

Their study, published in the Journal of Consumer Research, sheds light on why people tend to over-serve themselves when given larger plates and bowls.

The researchers found that our susceptibility to over-serve ourselves has to do with the Delboeuf illusion, first discovered in 1865. This illusion leads people to perceive two identical circles positioned side by side as dissimilar in size if one is surrounded by a large circle and the other by a smaller circle. They perceive the latter as larger.

When it comes to dinnerware, this means that people (even expert nutritionists) tend to exceed a target amount of food (the inner circle) when the outer circle (the plate’s edge) is much larger in diameter.

The researchers found that diners can lessen the effects of this illusion by heightening the color contrast between their food and dinnerware. The study showed that experimental participants served themselves considerably more when they scooped white-sauce pasta onto a white plate than red-sauce pasta onto white dinnerware.

"White on white or red on red doesn't provide enough visual contrast between the target serving area and the outer edge of plate, increasing one's tendency to over-serve onto larger dinnerware and to underserve onto smaller dinnerware," van Ittersum explains. “Those who own larger dinnerware in different colors may want to choose the color that highly contrasts with the food they are serving to minimize over-serving biases."

While greater color contrast between food and plate can be beneficial to those watching their weight, over-serving tendencies also can be reduced by decreasing the contrast between dinnerware and tablecloth, the study shows. “If you place a white plate on a white tablecloth, the Delboeuf illusion is lessened because the outside circle essentially disappears and you only focus on the inside circle, which is the target food area,” van Ittersum explains.

For nearly 150 years, the Delboeuf illusion was regarded as of little practical value, note the researchers in the study, titled “Plate Size and Color Suggestibility: The Delboeuf Illusion’s Bias on Serving and Eating Behavior”

“In the context of serving behavior, however, it takes on an undiscovered dimension of every importance….,” they write. “Over time and time with repeated meals, the gradual impact on one’s weight gain would be significant.”

Just understanding the phenomenon of the Delboeuf illusion probably isn’t enough to visually compensate for its effects, they say. “In the midst of hard-wired perceptual biases, a more straightforward approach would be to simply eliminate larger dinnerware – replace our larger bowls and plate with smaller ones or contrasting ones,” write the researchers.

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