Contour Bias is a well-studied theory that shows that humans prefer rounded objects and choices over angled ones. The more angled, the more that human brains reacted with activity in the brain associated with fear and flight. The studies also made sure to remove objects that might normally have a fear based reaction, such as knives.
In this illustration, I show rounded objects and the same objects modified to have a more angular form. According to theory, you should be more attracted to, or choose, the more rounded form.
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