The Delbouef Illusion is described as follows. If you place two equal circles beside each other, one without a rim (or concentric circle) and one with a rim, then, the one with the rim will appear larger. This week, in the International Journal of Obesity, researchers used this illusion to see changing the rims on plates altered an individual’s assessment of the amount of food on a plate.
In their study, researchers had individuals estimate the amount of food on plates without rims, with different rim colors, and with different rims sizes. Compared to plates with thin rims, individuals overestimated the amount of food on a wide rimmed plate by 5 to 10 percent. The effect of wide rims was greatest when food portions were larger. Compared to plates with uncolored rims, participants overestimated the amount of food on a plate by 1.5 to 3 percent when rims were colored.
While this study did not assess whether or not individuals were tricked into eating less or feeling fuller, the authors concluded that increasing a plate’s rim size and adding color might help someone to lose weight.