Explanation
-듯이 links two clauses so the second happens in the manner of the first: 'as', 'like', 'as if'. It attaches straight to a verb or adjective stem (알다 → 알듯이, 쓰다 → 쓰듯이) and to a noun through 이다 (학생이듯이); the 이 is often dropped (알듯). The spaced -(으)ㄴ/는 듯이, built on the dependent noun 듯, means 'as if it were the case', while -처럼/같이 compares nouns rather than actions. 그는 숨 쉬듯이 거짓말을 해요 — He lies as easily as he breathes.