Helmholtz Versus Haute Couture: How Horizontal Stripes and Dark Clothes Make You Look Thinner.

Antonis Koutsoumpis,Elias Economou,Erik Van Der Burg

doi:10.1177/03010066211038158

Abstract

In Helmholtz’s illusion, a square with horizontal stripes appears taller than an identical square with vertical stripes. This effect has also been observed in experiments with human stimuli, where a human figure wearing a dress with horizontal stripes appears thinner than a drawing clad in vertical stripes. These findings do not agree with the common belief that clothes with horizontal stripes make someone appear wider, neither do they disentangle whether the horizontal or vertical stripes account for the thinning effect. In the present study, we focused on the effect of horizontal stripes in clothes comparing horizontal stripes against no-stripes (not against vertical; Experiments 1 and 2), using photos of a real-life female model, and controlling for the average luminance of the stripes (Experiment 2). Results showed that horizontal stripes and lower luminance have—independently—a small-to-moderate thinning effect on the perceived size of the body, and the effect is larger when the two variables are combined. In Experiment 3, we further show that the thinning effect due to the luminance of the dress is enhanced when the general background gets darker.

Highlights

In Helmholtz’s illusion, a square with horizontal stripes appears taller than an identical square with vertical stripes
The first to report a thinning effect of horizontal stripes was Helmholtz (1867/1962) who showed that a square filled with horizontal stripes was perceived as taller than an identical square filled with vertical stripes, an effect known as the Helmholtz illusion
The results showed that, when the luminance of the stimuli and the background luminance were held constant, horizontal stripes seemed to account for the thinning effect, regardless of any stimuli or background luminance effect

Summary

Introduction

In Helmholtz’s illusion, a square with horizontal stripes appears taller than an identical square with vertical stripes. Participants saw the image of a female model wearing a shirt with either horizontal or vertical stripes and asked participants to match the size of the vertically striped stimulus with thinner and wider versions of the horizontally striped stimulus They manipulated the body size of the model (creating a thinner and an oversized version of the figures) to test whether the effect persists across different body sizes. Imai (1982; as reported by Ashida et al, 2013; original paper in Japanese) using the drawing of a— rather overweight—male figure wearing either a horizontally or vertically striped shirt, found that the vertically striped stimulus was judged 15.37% thinner than that with horizontal stripes These findings suggest that for larger body sizes horizontal stripes have a widening effect, opposite to the Helmholtz’s illusion

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