The 24px are somewhat arbitrary, based on the idea that 18px/1.25 line height are comfortable to read. The circle is trying to illustrate that repetition somet

The 24px are somewhat arbitrary, based on the idea that 18px/1.25 line height are comfortable to read. The circle is trying to illustrate that repetition sometimes feels oddly satisfying to us. I don't think the text does a good job of explaining it. I"m not sure there even is a known explanation, but it's certainly a phenomenon everywhere from dance music to architecture. I'd venture a guess and say the brain actually hates all the pattern matching it has to do and enjoys stumbling on simple rules that explain something.