Difference between 「~がる」 and 「～そう」


「～がる」と「～そう」の違いは何でしょうか。感覚的に同じではないことは分かりますが、説明はできません。どうも「～がる」形はもはや口語ではあまり使われないように感じます（「怖がる」「怖そう」などの完全に意味が変わる形容詞を除く。）。そういったレジスター(言語使用域)の違いも含めての回答を期待しています。もしこの質問がDuplicateであれば、元の質問を教えていただければ幸いです。




I think the difference mainly lies in the following.

The ～がる forms make an assumption about the described person's internal state,
whereas the ～そう form is a statement about the person's external appearance.
(Maybe a bit like the difference between sympathy and empathy.)

For example for 寒がる・寒そう, using 寒がる refers to your empathizing with the person
who is cold, whereas 寒そう describes the person who is cold as "looking cold".

In English the difference might be expressed as

> He must feel very cold.  
>  He looks (as though he is) very cold.

The ending ～たい gives the pair たがる・たそう. 食べたがる sounds more like someone is
craving something; 食べたそう sounds more like someone looks like s/he wants to eat
something (but chooses not to for reasons of politeness, for example). The
former description is more emotional than the latter.

