This mightn't answer your question but it seems related: https://en.wikipedia.org/wiki/Default_mode_network

I totally get what you're saying!

My personal example is when I finish a task, my default action is to have a cigarette, and/or look at my phone.

I don't know if it directly explains these actions or not, but psychology uses the term schema for "pre-programmed" responses to stimuli.

For example, if there was a dog that bit you as a kid, your mind will remember that, and the next time you see a dog, your brain will default to "stay away". If you encounter friendly dogs after that, your schema will change to "proceed with caution" as it now knows that dogs can be nice, but it'll remember that bite.

They are mental shortcuts. Instead of completely analyzing the current situation and creating a plan from scratch, your brain remembers the last similar experience it had, and proceeds as if they are pretty much the same.

I'm thinking this relates to your "default actions" as: I was bored before, and when I did X, it caused the boredom to go away, so I'll try that first. And it just kind of happens without you consciously deciding to do it.

Also, if I'm the only person that understands what you're talking about, you might be describing a trait of ADHD. I used to think a lot of the things I experienced were completely normal, but eventually figured out that I'm very neurodivergent.

Automaticity? https://en.wikipedia.org/wiki/Automaticity

Can you give some concrete examples? I can't really relate to what you call "default action".

I think you may be referring to the status quo bias.

It seems like you're describing a model that helps you understand or reason about or predict your behaviour or that of others.

Im sure that similar things exist in the formal science of psychology, even if they have different terminology.

Cognitive Behavioural Therapy deals with this in a way. In the same way we have physical habits, we also have cognitive or thinking habits.

For example, if you're in the habit of thinking that high school acquaintances remember all the embarrassing things that happened in that period of your life, then your default behavior when you encounter someone at the supermarket might be to pretend not to recognise them and turn down an aisle. If you challenge that assumption by reminding yourself that you dont really think about things other people did in high school, then your new default behaviour might be casual disregard for those people.

As an aside, for me personally "forcing" myself to do things doesn't work. For example, forcing myself to jog every day will make me miserable because I hate jogging. OTOH riding every day feels like a really satisfying achievement because I do really enjoy riding.

https://en.wikipedia.org/wiki/Operant_conditioning

?

Wouldn't that basically be any action that didn't start in the prefrontal cortex? There are plenty of fauna that are basically entirely composed of "default action".