translation.en: Well, let's first look at the probability -- and this is very, very difficult to estimate -- but there have been only four studies on this in recent years, which is surprising.
translation.zh: 让我们来看看可能性—— 这非常难估量—— 但近年来，这个领域只出现了四篇研究文章。 这很让人吃惊。