Researchers have long known that large dinnerware can sabotage people’s diets. But a groundbreaking new study suggests the contrast of a plate or bowl with what’s placed inside it can also make us fat.
Reporting in the Journal of Consumer Research, investigators found that low colour-contrast between dinnerware and food — say, vanilla ice cream heaped into a white dish — significantly increases the likelihood of people over-serving themselves, while a higher contrast minimizes such behaviour.
Researchers say it’s all because of an optical illusion discovered more than 150 years ago — one that, until now, has been considered “of little practical use.”
The Delboeuf illusion finds that if two identical circles are placed side by side, one surrounded by a much larger circle and the other by only a slightly larger circle, people falsely perceive the inner circles as dissimilar in size.
Researchers Brian Wansink and Koert van Ittersum say this curious phenomenon helps explain why people — including nutritionists, who know better — consistently over-serve themselves when given larger dinnerware: they perceive the middle space on the dish as larger than it really is.
“It’s not simply that the bowl holds more,” says van Ittersum, the study’s lead author. “Even when you give people a specific target amount, they’ll pour more than the target into a big bowl, and less into a small bowl, because of this illusion.”
And because it’s the inner and outer circles that power the visual trick, the colour contrast between the two has a significant effect on serving behaviour. For example, study participants placing white pasta into a white dish served themselves significantly more than those placing red pasta into a white dish.
“If you want to reduce the amount of unhealthy food you eat, you want to choose a plate that really contrasts with it; if you plan to eat healthy food and want to eat more, you want to choose a plate with a lower contrast,” says van Ittersum, an associate professor of marketing at Georgia Institute of Technology.
Importantly, the researchers found that a table or tablecloth similar in colour to the dinnerware significantly diminished over-serving tendencies. This, again, comes back to the Delboeuf illusion.
“If you put a white plate on a white tablecloth, the illusion kind of disappears because you eliminate the outside circle and just focus on the inside circle,” explains van Ittersum.
Laughing, he says it’s “all very technical.” But the bottom line is that choosing dinnerware based on its size and contrast with the food or table is a much more effective strategy than education.
“Even when we tell people, ‘Listen, this illusion takes place, so please be careful when you serve yourself food,’ they still mess up,” says van Ittersum. “So at home, it’s especially important to take these preventive measures.”
As the journal article puts it, it’s easier to change our personal environment than to change our mind.
source: Times Colonist