Cultural Effects on Visual Perception

Cultural Effects on Visual Illusion

In the literature of psychology, optical illusion is often used as evidence of human universals in perception. One of the most famous optical illusions is the Müller-Lyer illusion (see Figure 1), in which people perceive that a line segment ending in inward-pointing arrows is longer than a horizontal line segment ending in outward-pointing arrows. This seemingly universal phenomenon, however, has been tested cross-culturally, and the results indicate cultural variations in the magnitude of illusion. For example, Murray Islanders in Melanesia and members of the Toda tribe in India showed significantly smaller errors than do their British counterparts in judging the relative lengths of the lines. Similarly, extensive cross-cultural studies of 17 societies—including a variety of African agricultural and hunter-gatherer cultures, an Australian Aboriginal foraging culture, a tribe of Filipino horticulturalists, and midwesterners in the United States—show that the degree of illusion is much stronger among U.S. residents. Furthermore, children in some cultures (e.g., hunter-gatherers from the Kalahari Desert) were completely immune to the Müller-Lyer illusion. The findings suggest that individuals who grew up in certain visual environments are not vulnerable to the Müller-Lyer illusion.

Figure 1 Müller-Lyer Illusion

Source: General Social Survey, National Opinion Research Center (2000).

Various studies have proposed hypotheses to examine the main causes of cultural variations in susceptibility to this illusion. The carpentered environment hypothesis, for example, suggests that people developmentally acquire perceptions of a three-dimensional world in accordance with their experiences with the surrounding environment. In Western industrialized societies, individuals' depth of field is founded on the structure of rooms, houses, and furniture consisting of vertical and horizontal lines with corners in a variety of angles. People in these societies associate acute angles with nearby objects (such as the corner of a rug), and obtuse angles with somewhat more distant views (such as the intersection of two walls and a floor). Once they acquire this specific perceptual pattern in the three-dimensional world, they apply the same rules even when they observe the visual representation in the two-dimensional field. The Western perspective in art is a good example. In Western perspective, objects close to the viewer are drawn larger and are characterized by acute angles, and objects farther from the viewer are drawn [Page 340]smaller and feature obtuse angles. For this reason, Westerners perceive a line ending in inward-facing arrows to be farther away (and therefore actually longer) than it appears. However, in cultures where structures are built using less angular shapes, people have fewer opportunities to interpret the relationships between lines and angles in their perceptual world. The carpentered environment hypothesis thus helps explain why people from some cultures are less susceptible to the Müller-Lyer illusion than Westerners.

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