Do Japanese people use formal or informal language for internal monologues?


I assume informal. Are there any cases when you would use formal, perhaps to
be sarcastic? And general, is informal or formal language used more in life (I
mean for the average person - is it around 50-50? Or lopsided to one
direction?)




I thought your question was a bit vague. Do you mean to ask if Japanese people
use 敬語/polite form when talking _among_ themselves? Or are you asking if they
think and talk _to_ themselves in 敬語?

Most of us learners learn 敬語, the formal style, first. That is usually the
first style of speech/writing we learn in our Japanese class. But for native
speakers it is different. Japanese kids use ため口/informal language growing up,
with parents and siblings. I seem to recall several newer Japanese
textbooks/online courses claiming that "teaching language learners です・ます first
is unnatural", citing as an important reason something to the effect that "the
traditional teaching methods have failed to accustom language learners to ため口,
but in reality ため口 is widely used by native Japanese speakers."

Most Japanese kids start to correctly and profeciently use です・ます（敬体{けいたい}）in
小３、小４ (3rd and 4th grade). (Heard this from my students. Some online sources
also seem to suggest age 10 is something of a watershed in terms of formal
language use. [「子供が敬語を正しく使い分けられるのは10歳頃からです。」](https://sengakuhisai.com/keigo-
nansai-kara/)) Enter 敬語（丁寧語・尊敬語・謙譲語）around 小５ (5th grade). By the time
Japanese kids enter middle school, they are fully adept at 敬語/formal style. I
have taught and tutored a lot of Japanese students from 中１ through 高３ (middle
and high school) English and math, and they interact with each other in
です・ます（敬語） when they are not yet on familiar terms. This is also the case in 塾
(cram school) where students don't necessarily get to know one another very
well or make friends. Of course at school it is a different story. A lot of
middle/high school students use ため口 at school with peers and people younger
than them. In the workplace 敬語 becomes the predominant style of speech.

@naruto's correction and supplemental information:

> Kindergarteners do understand and use basic ですます style. Folktales like
> [桃太郎](https://en.wikibooks.org/wiki/Japanese/Reader/Momotaro) are told in
> that style, and 1st graders write diaries and compositions using です/ます (it's
> not something we study explicitly, though). In the 4th grade they start to
> learn romaji.

In terms of 独り{ひとり}言{ごと}, when they talk to themselves, most Japanese people
use ため/informal language, of course.

