The people from this study investigated diners' perception of the sweetness of three desserts based on the plate color they were served in (which where black or white).

Study Design

253 diners, most of who were French, who volunteered to participate in this study. This is a nonrandomized experiment since the participants volunteered and were not randomly chosen from the population but the dessert they were served were randomized. Thus each dessert was randomly chosen to be served on a different days and the color plates were also randomly chosen to be served during either lunch or dinner..

From their research they found that on average dessert B was perceived sweeter than A and C regardless of the plate it was served in. They also saw that only this dessert B was on average perceived sweeter when served in a black plate while the opposite was observed with dessert A and C. Thus the claim they make in the article is not completely justified since there's more to it than explained in the article.