It seems to me that the little sister is acting rationally. Yes it's a bit lazy but then: when was the last time you used a calculator for a calculation that you could have done in your head? Do you actually need to be able to do mental arithmetic, do you actually really need to be able to work out what 24 + 7 is in your head?

I don't know what the answer is. I'm old school, if it was up to me I'd bring back slide rules and log tables, because that's such a visual and tactile way of getting to know mathematics and numbers.

It's interesting to consider how AI is affecting humans' cognition skills. Is it going to make us stupid or free us up to use our mental capacities for higher level activities? Or both?

Even with a calculator and more so with ChatGPT, you still need to know whether an answer passes the sniff test.

Only in a few fields. You can have a successful career publishing papers in the social sciences, or justifying decisions in middle-management, without being able to know whether an effect size passes the sniff test - actually not knowing will probably help you make convenient mistakes.

24 plus 7 is 41 or 94 or 3 and 4/7 are all obviously wrong, but only if you have developed number sense. I've had students who wouldn't bat an eye at any of those solutions.

One thing missing from the reddit story is how the author knows their sister is using ChatGPT to obtain the answer as opposed to validating work. I'll often punch a calculation I've already done in my head into a calculator to confirm for myself I landed on the right answer. Or come up with a solution to a problem, find myself wondering if there's a better solution or just feel like it doesn't quite look right and search for solutions online to compare and contrast. I'm not using the calculator or search to replace my work, I'm using it as the sniff test. But you couldn't determine that just by knowing my inputs to the calculator and google. You'd have to see the entire process.