Monday, September 24, 2018

Are you weird?

Please go back for a moment to my last week’s blog and look at the picture of the Müller-Lyer Illusion. The weird thing of this figure is – and that’s why we call it an illusion – that the upper line looks shorter than the line under, though actually the lines have the same length. Or don’t you see the illusionary difference of length of the lines? If so, probably then you are not weird, or rather you are not WEIRD, for especially people from Western, Educated, Industrialized, Rich and Democratic societies are tricked by the figure. In other words, whether you see the illusion or don’t is culture dependent. This is not only so for this illusion but for other illusions as well. But let me here concentrate on the Müller-Lyer Illusion as an instance of all illusions.
This illusion has been first described in 1889 by Franz Müller-Lyer. Since then several psychological explanations have been proposed. However, all tests of the illusion have been done by investigators with a Western background and almost everybody who has seen the illusion has this background as well. Therefore, it wasn’t realized that the illusion might be a WEIRD phenomenon. This changed in the 1960s when it was realized that seeing the illusion might have been influenced by cultural experiences. So Marshall H. Segall, Donald T. Campbell and Melville J. Herkovits got the idea that people living in different kinds of environments may see the illusion in different ways. To test this idea they selected peoples living in different physical environments, varying from environments with mainly straight lines like big cities with sky scrapers to environments with chiefly winding and varying lines like you find them in wood areas. Teams of data-collectors were sent to peoples in 15 different environments who were asked to estimate the length of the lines in the Müller-Lyer Illusion; or rather they had to judge the difference in length. In their summary of the project the investigators don’t specify the peoples involved but – to give an idea – you have to think of inhabitants of New York as opposed to Kalahari hunter-gatherers, Suku tribespeople from Northern Angola, and Bete tribespeople from the Ivory Coast. Care was taken that the test persons were not influenced by the data-collectors and, as said, the test had been developed that way that the informants could indicate what according to them the difference in length of the lines in the pair was, in case they saw a difference. (Actually, they had to judge not only the Müller-Lyer Illusion but four other illusions as well.) And what happened? The illusion appeared to be an illusion. Or rather some saw differences in length between the lines, but the differences were different for different peoples; in addition the differences were zero for some. Moreover, to what extent people were susceptible to the Müller-Lyer Illusion was dependent on the environment where they lived. People from Western societies – societies characterized by straight lines – proved to be more susceptible to the Müller-Lyer Illusion than non-Western peoples, i.e. for the former the difference in length was more than for non-Westerners. Also among the latter for some the difference in length of the lines was more, for others less, dependent on the environment where they lived. In other words, seeing the illusion or to what extent you see it depends on the culture where you live. In an older blog (dated 22 June 2009) we have seen that whether a certain epistemic intuition is really an intuition for you depends on your social-economic background. Here we have an example of the fact that illusions are culture dependent. Often it is so that mental and visual perceptions are related to cultural differences. And if you are weird you see illusions where others maybe don’t. But since the whole world still becomes more westernized to some degree, it’s not unlikely that in future more and more people will become weird.

References and related websites
- Barthelme, Simon, “Culture and Perception, part II: The Muller-Lyer illusion”:
- Donaldson, J; F. Macpherson, “Müller-Lyer” (Some explanations of the Müller-Lyer Illusion):
- Schulz, Colin, “Are Optical Illusions Cultural? People from around the world respond to optical illusions different. But why?”:
- Segall, Marshall H.; Donald T. Campbell; Melville J. Herkovits on their research:
- Wade, Lisa, “Cultural differences in cognitive perception” (Some statistics of the research by Segall et. al.):

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