After learning Korean for six years, one of the things that still not perfectly clear for me is the usage of 더니 and 았/었더니. I feel like I now know so much, yet at the same time it feels like grasping at sand and watching it flow through between my fingers.
I’ve tried coming up with up practical situations where you would need to use these grammar patterns and try to highlight their functionality. If you’ve already read the “rules” of these two grammar patterns, chances are you probably are still incredibly confused. I hope after reading these examples you can get some “feelings” about it on top of the grammar rules.
Difference between 더니 vs 았/었더니
1) 더니 leans towards expressing an observation while 았/었더니 leans towards expressing causation.
A: 아까 비가 오더니 이제는 구름이 없네
B: 아까 비가 왔더니 이제는 구름이 없네
A) speaks of observing rain some time ago and then observing the lack of clouds now. There is no implication of why there is no clouds now. B) implies that there is no clouds now because it was raining before.
A) 유진이가 술을 마시더니 얼굴이 빨개졌어
B) 유진이가 술을 마셨더니 얼굴이 빨개졌어
In A) the causal link is very weak whilst much stronger in B). In A) you are only just recollecting an observation.
2) 았/었더니 is unnatural when talking in the 3rd person
A) 유진이가 그 남자를 때리더니 뛰쳐나갔어
This is what you would say if you were at a restaurant and your friend comes back and asks “where did 유진 go?”. 때렸더니 is not appropriate here.
B) 아까 유진이가 들어오더니 돈을 식탁에 뒀더라
3) Difference between 았/었더니 and 니까 or 아/어서
A: 어제 비가 왔으니까/와서 오늘 구름이 없어
B: 어제 비가 왔더니 오늘 구름이 없네
Notice sentence A) ends in a standard ending while B) ends in the 네 ending. Both are causal sentences, but 왔으니까/와서 leans towards an expected outcome whilst 왔더니 leans towards an outcome that is not necessarily expected.
4) Difference between 더니 and 는데
A) 네가 아이스크림을 안 먹겠다고 히더니 다 먹었어!
B) 네가 아이스크림을 안 먹겠다고 했는데 다 먹었어!
Sentence A) expresses an observation and expresses that the outcome is somewhat unexpected. Sentence B) says they have eaten it whilst providing background information that they said they wouldn’t eat.
A) 민준이가 아까까지만 해도 자고 있더니 지금은 공보하네
B) 민준이가 아까까지만 해도 자고 있었는데 지금은 공부하네
The difference here is quite small. Both are speaking of a temporal change whilst using the events in the first clause as a basis for what happens in the second clause. However A) includes a bigger nuance of something unexpected happening.