I read that certain optical illusions are not experienced as strongly by native, non-city-dwelling populations. It was hypothesized that this was due to the rel

I read that certain optical illusions are not experienced as strongly by native, non-city-dwelling populations. It was hypothesized that this was due to the relative absence of 90-degree angles and "carpentered" features in their environments [1]. Looking it up again now to refresh my memory, I see that this explanation is contentious and there may be other reasons for the variation. The Wikipedia page also mentions papers about pigeons [2] and a parrot [3] reportedly being susceptible to the illusion. I'm pretty sure the birds used in those experiments live in carpentered environments that are heavy on the 90-degree angles. A Smithsonian magazine article on the same topic says that "a computer trained to mimic the perceptions of the human eye was also susceptible" [4]. [1] https://en.wikipedia.org/wiki/M%C3%BCller-Lyer_illusion#Variation_in_perception https://en.wikipedia.org/wiki/M%C3%BCller-Lyer_illusion#Vari... [2] http://sci-hub.ac/10.1037/0735-7036.120.3.252 http://sci-hub.ac/10.1037/0735-7036.120.3.252 [3] http://cavlab.net/wp-content/uploads/2009/04/cavangh2008processing-of-the-muc2ab-ller-lyer-illusion.pdf http://cavlab.net/wp-content/uploads/2009/04/cavangh2008proc... [4] http://www.smithsonianmag.com/smart-news/are-optical-illusions-cultural-6633978/ http://www.smithsonianmag.com/smart-news/are-optical-illusio...