But it's not a matter of stupid/smart. It's actually the same reason why Paul Graham's 'Hackers and Painters' analogy is so apt. The reality is that some people can think in abstract terms, while others cannot.
Someone who can think in abstract terms can be a graphic artist or a programmer. Consider that even in mathematics, the most concrete things are numbers, which are completely abstract. If you understand that, then guess what? You can think in abstract terms.