My earliest clear memory is that of my 4th birthday, from the moment I woke up to a couple of hours later. I remember my mom telling me to get dressed up so we can go to the daycare and after to school, which I started to do and then thought “what’s school? what’s daycare?” (these I asked) “why are you my mom?” (this one I didn’t for some reason). After being fully dressed, we got into the car and drove to the daycare, I was guided to a room that’s next to the kitchen and told to wait. A couple of minutes later, I notice a light coming from the hallway connecting to the kitchen (“what’s that? why is it coming closer?”), then the nanny, her husband and my mom come out with a cake. I then immediately asked why there was a cake, I was told it’s my birthday, and then I asked what’s a birthday.
So yeah I think kids ask a lot of questions the moment or around when they start to be self-aware.
I wouldn’t say it’s when they’re self aware. Kids can recognize themselves in a mirror at around 1 year old. They start asking why when they realize other people know things they do not, a concept usually called “theory of mind”.
Some kids ask “why” because they understand the question and want to know more, but that isn’t the only reason.
Asking “why” tends to result in people talking to you. Ever hear a kid ask “why” over and over again without caring about the answer? They may have been asking the question because it provides them with attention. It’s a single word that nearly guarantees an adult will talk to you, and sometimes that’s all a kid really wants.
I work with babies under 1, even they can point to pictures to “ask” me to name them. Knowing others know stuff is basic.
Theory of Mind isnt something we use in my field, but from a quick glance it’s knowing other people have minds, that they have their own desires, feelings, thoughts, etc not that they know information.
In ECEC terms we would think of that as the end of their egocentric stage. Usually seen around 1-3.