Small children have a short attention span.

幼儿注意力持续时间短。

《牛津词典》

I have a short attention span. I just can't concentrate.

我是个注意力很不集中的人，无论如何就是无法专注。

youdao

Remember that your answer must fit a short attention span; try to respond only to the question asked, giving your child just the information he asks for and he can handle.

请记住，儿童的注意力是很短暂的，所以你的回答要尽量简明扼要，有针对性的回答孩子的问题，只告诉他们想知道并且又在他们理解能力内的内容。

youdao

As far as trading these markets, you certainly need to have a short attention span.

FORBES: How To Trade This Market Meltdown

The parents were amazed that their kids, normally with a short attention span, instantly took to solving the puzzles that we presented.

FORBES: Japanese Secret Boxes: The Coolest Security Puzzles for Kids and Adults

The internet, and by extension, popular opinion among a broad swath of humanity, has a short attention span, for better and for worse.

FORBES: 'Good Guy Pope' Meme on Reddit is a Win for Pope Francis