Nuances between 思わず, うっかり, つい, and 知らず知らず


I've looked at things explaining the differences between the 4 words (思わず,
うっかり, つい, and 知らず知らず), but I still end up confused with the explanations and
examples. I get that 知らず知らず is more of a thing with long term actions, but
beyond that, I'm still confused.

Some examples according to [this thesaurus
page](https://dictionary.goo.ne.jp/thsrs/3357/meaning/m0u/):

  1. 知らず知らず本音を吐く is odd, but replacing 知らず知らず with any of the others is not.
  2. In 思わず痛いと叫んだ, it can't be replaced with any of the others. I get why not 知らず知らず, but why not the others?
  3. 疲れてうっかりうとうとする is odd, but replacing うっかり with any of the others is not
  4. In あまりのうれしさに知らず知らず涙があふれた, 知らず知らず can't really be replaced with the others. Why not?




I think the linked page says it all more or less.

  1. 知らず知らず is used when you started doing something (shedding tears) and it takes a while for you to notice what you are doing.

  2. つい is used when you did things by habit or mistake, due to lack of contemplation.

  3. うっかり is used when you did things by mistake or accident. Usually it is about doing things you are supposed not to do.

  4. 思わず is used for instantaneous reactions.

So, as for the questions,

  1. 本音を吐く is a short-term action and 知らず知らず is not natural. 本音を漏らす could work with 知らず知らず. (You are pretending at first, but gradually you start telling truths without intending it.)

  2. It is a reaction.

  3. I think it is subtle. For example, in a meeting you are not supposed to nod off, うっかりうとうとした is ok.

  4. It is a typical situation for 知らず知らず. As the table suggests, うっかり is the only impossible one, because it is by no means something you shouldn't do.

* * *

つい and うっかり probably overlap most (ついうっかり is a common combination which is
closer to うっかり than つい), but just one explanatory example. Consider

  * ついお菓子を食べてしまった

This is natural when you think eating sweets is something you are (vaguely)
guilty about.

  * うっかりお菓子を食べてしまった

is natural when you are supposed to eat nothing for medical check, for
example.




I think the linked page says it all more or less.

  1. 知らず知らず is used when you started doing something (shedding tears) and it takes a while for you to notice what you are doing.

  2. つい is used when you did things by habit or mistake, due to lack of contemplation.

  3. うっかり is used when you did things by mistake or accident. Usually it is about doing things you are supposed not to do.

  4. 思わず is used for instantaneous reactions.

So, as for the questions,

  1. 本音を吐く is a short-term action and 知らず知らず is not natural. 本音を漏らす could work with 知らず知らず. (You are pretending at first, but gradually you start telling truths without intending it.)

  2. It is a reaction.

  3. I think it is subtle. For example, in a meeting you are not supposed to nod off, うっかりうとうとした is ok.

  4. It is a typical situation for 知らず知らず. As the table suggests, うっかり is the only impossible one, because it is by no means something you shouldn't do.

* * *

つい and うっかり probably overlap most (ついうっかり is a common combination which is
closer to うっかり than つい), but just one explanatory example. Consider

  * ついお菓子を食べてしまった

This is natural when you think eating sweets is something you are (vaguely)
guilty about.

  * うっかりお菓子を食べてしまった

is natural when you are supposed to eat nothing for medical check, for
example.

