[odhiopog] Count with your eyes closed

Relax, close your eyes, and count numbers.  How far can you get before your mind wanders?  How much mental concentration does it take?

Or, sing Happy Birthday in your head.  How many times can you repeat before you find yourself thinking of something else?  Inspired by washing hands for COVID-19.

Hypothesize that these tests can be used to measure mental state, how frazzled your mind is.