Abstract
It is popularly believed that wearing horizontal stripes makes us look fatter than we are. This appears to contradict two well-known illusions: the Oppel-Kundt illusion shows that a filled extent looks longer than an unfilled extent and secondly the Helmholtz square illusion shows that a square comprising horizontal lines appears taller than one of identical size comprising vertical lines. These effects are very closely related and both suggest that the wearing of horizontally striped clothes should make us look taller and thinner. Indeed Helmholtz claimed that “ladies' frocks with cross stripes on them make the figure look taller”. Recent work by Taya & Miura (2007) suggests that a resolution of this paradox may lie in the difference between 2-D pictures and 3-D bodies. Using 2-D images of vertically-oriented cylinders they demonstrated that there was a significant positive correlation between the apparent 3-D depth of the cylinder and an illusory shrinkage in the cylinder's width. These results suggest that the wearing of vertical stripes makes us look slimmer by way of providing cues to the 3-D nature of our bodies and that this effect outweighs the ‘fattening’ ‘Helmholtz square’ effect of the vertical stripes. We have (1) confirmed Helmholtz's findings that a square composed of horizontal lines looks taller than one made of vertical lines; (2) determined that when the horizontal and vertical stripes are presented in the context of 2-D images of patterns on women's clothing the illusion is negated and (3) demonstrated that patterns that accentuate 3-D information and use horizontal stripes will make us look even slimmer. These results will be discussed in the context of the possibility that (1) the belief that wearing horizontal stripes makes us look fat is a recent myth and (2) fat people just like wearing horizontal stripes.