少根筋

她有點少根筋，常常忘東忘西。

She's a bit of an airhead, always forgetting things.

他少根筋，說話不經大腦。

He's clueless and says things without thinking.

你是不是少根筋？這麼簡單的事都搞不懂。

Are you an airhead? You can't even understand something this simple.