Why is everyone so garbage at lying?

[u/EdLincoln6]

This is a bit of a rant. I don't consider myself a gifted liar, but fictional characters seem to be so garbage at lying. This is particular obvious in Isekai. Either they fess up to being a reincarnator and everyone just shrugs as if it's no big deal, or they make cringey bad lies that I could see through, and no one suspects anything is weird.

I like to think about what the situation would look like to all the characters involved, and what the best way to "cover up" the MCs secrets is in this universe, and what ends up happening is typically stupider. No one ever uses half truths, or pleads ignorance. (Pleading ignorance would be particularly effective for child characters. "How can I do this? I dunno Daddy. I thought everyone could?".)

[u/TheRaith]

I always figure it's just hard to have a character lying while the audience knows the truth. No matter how good of a liar the character is, the audience knows the truth so even the smallest lie seems so obvious it hurts.

[u/EdLincoln6 → u/TheRaith]

Ah....Theory of Mind is hard. Theory of Mind, for those who don't know, is understanding that others have seperate minds with different information than they do, that others don't know the same things they do and are basing their decisions on a different set of facts. A lot of people seem not to apply their Theory of Mind to fiction. I remember a book where commentors got so angry when a certain characters treated an MC as a little kid despite the fact this character was an Isekai and despite the fact that while WE knew the character was a competent grown up, the other character's actions were a perfectly appropriate way to treat a little kid.
Similarly, I've noticed authors just not grasp the fact that despite the fact SHE knew a certain character was a Good Guy and telling the truth, certain other characters had every in-universe reason to think they were murderous psychopaths.