Circumscribed shapes are enlarged: is this a variation of the Delboeuf illusion?

Pairs of complex shapes, for example, two golf holes or two hands making a peace sign, were printed on cards with one of the two shapes surrounded by a circle. 20 participants judged the size of the unenclosed shapes relative to the size of the enclosed ones. For 12 pairs in which there were physical differences in size of the two shapes, participants made veridical judgments. More importantly, for the six pairs in which the unenclosed and circumscribed shapes were the same size, the unenclosed shapes were judged smaller than the circumscribed ones. Thus, a novel illusion in which surrounding circles perceptually enlarge a variety of interior shapes is demonstrated.