Take this peculiar analysis by students of YGA university for example.
see this random shape?
now see this.
If one were to ask you to pick an image, in most cases you would pick Fig 2.
The amygdala is the part of the human brain that "feels" emotion.
Studies have shown that the human mind more readily accepts shapes that are don't have extreme contrast.
Acute angles in diagrams are less liked than obtuse ones.
The mind will more readily accept an acute angle if there is some amount of reduction in the sharp edges. Hence the smoother picture (Fig 2) is subconsciously picked.