I know a child that can correctly solve 15-20 single-digit addition problems per minute normally, and 45-50 per minute with an 8-hour medicine related to Ritalin. The child has no sense of time themselves, but you can tell within about 15 minutes when the 8 hours wears off and the very well-behaved child completely loses the ability to focus.
Again, there is no measurable physical test. It’s a behavioral observation.
And, it’s well documented that Ritalin and the like help anyone, not just those diagnosed ADHD, do better at repetitive tasks.
You have to notice - Ritalin et al are used to make a person conform to a specific environment, whether that’s sitting at a desk in school for 6 hours, or an assembly line, or the cubicle farm.
In prior years, we did other things that worked better without drugs. Schools didn’t push academics at age 4-5, we gave the kids more recess, kids had more physical play
at home and at school, there were shop classes, and there was more discipline of course, both at home and at school.
For my part, what you describe is a trained monkey.