Visual illusions and plate design: the effects of plate rim widths and rim coloring on perceived food portion size

Abstract

OBJECTIVEThe Delboeuf Illusion affects perceptions of the relative sizes of concentric shapes. This study was designed to extend research on the application of the Delboeuf illusion to food on a plate by testing whether a plate’s rim width and coloring influence perceptual bias to affect perceived food portion size.DESIGN AND METHODSWithin-subjects experimental design. Experiment 1 tested the effect of rim width on perceived food portion size. Experiment 2 tested the effect of rim coloring on perceived food portion size. In both experiments, participants observed a series of photographic images of paired, side-by-side plates varying in designs and amounts of food. From each pair, participants were asked to select the plate that contained more food. Multi-level logistic regression examined the effects of rim width and coloring on perceived food portion size.RESULTSExperiment 1: Participants overestimated the diameter of food portions by 5% and the visual area of food portions by 10% on plates with wider rims compared to plates with very thin rims (P<0.0001). The effect of rim width was greater with larger food portion sizes. Experiment 2: Participants overestimated the diameter of food portions by 1.5% and the visual area of food portions by 3% on plates with rim coloring compared to plates with no coloring (P=0.01). The effect of rim coloring was greater with smaller food portion sizes.CONCLUSIONThe Delboeuf illusion applies to food on a plate. Participants overestimated food portion size on plates with wider and colored rims. These findings may help design plates to influence perceptions of food portion sizes.

Sensitivity to portion size of unhealthy foods

“…Further, the reduction in sensitivity with increasing portion size might be addressed in part by presenting all stimuli on a constant-sized plate, which might enhance the salience of the larger portion sizes. Prior work suggests manipulating characteristics of plates, such as size or rim width, may improve portion-size perception and decrease consumption (McClain et al, 2013;Pratt, Croager, & Rosenberg, 2012). In either case, the data from this study suggest that while participants are sensitive to smaller portion sizes, it may be possible to increase portion-size sensitivity to larger portion sizes.…”

Whether Smaller Plates Reduce Consumption Depends on Who's Serving and Who's Looking: A Meta-Analysis

“…This research fits within a larger field of small ways in which the amount we consume can be potentially limited by portions served such as smaller plates (shown in this article), smaller "food units" (Davis et al 2016), smaller portions (Zlatevska et al 2014), partitioned portions (Holden and Zlatevska 2015), or conversely, encouraging people to eat less by making portions appear larger (e.g., Wansink andVan Ittersum 2003, 2006;McClain et al 2014).…”

Weighing the Evidence of Common Beliefs in Obesity Research

“…There is wide-spread evidence that one robust driver of self-served portion sizes is the size of the plate upon which the food is served. Within a normal American plate size range of 24-30 cm, the smaller plates have been shown to consistently – and unknowingly – decrease how much food one serves by up to 22% 417,424 . (Importantly, when plates become too small the cease to have this intended effect, partly because of refills and reactance) 425,426 .…”