“A preference for circular shapes is deeply ingrained in all of us from birth. A 2011 eye-tracking study found that at five months of age, before they utter a word or scribble a drawing, infants already show a clear visual preference for contoured lines over straight lines.

In a seminal paper published in 2006 in Psychological Science, cognitive psychologists Moshe Bar and Maital Neta conducted an experiment in which 14 participants were shown 140 pairs of letters, patterns, and everyday objects, differing only in the curvature of their contour. The results were not completely surprising: participants showed a strong preference for curved items in all categories, particularly when it came to real objects.”

Lima, M. (2017)

There are many proverbs and sayings that have to do with form characteristics and emotions. Straight: honest, easy, good, docile, obedient, calm, fair.
Lakoff and Johnson (1999)