Years ago I tried starting out with 5 wpm and 'working up', and just barely passed the 13 wpm test to get the 'Advanced' ticket. Only thing that stopped me getting Extra was that 20 wpm code test, that was still a thing in the 80s.
I let it all lapse for about 35 years and just got back into radio in '22, and tried copying some 5 wpm from W1AW, and could copy maybe 20 or 30% of that at best. So it came as something of a surprise, playing with Morsle for a few minutes, to discover I can do as well or better at 35 wpm as I can at 5.
You really get too much time at the slow speeds to engage the frontal cortex. If you learn to think your way to each letter, that doesn't scale very far.
I let it all lapse for about 35 years and just got back into radio in '22, and tried copying some 5 wpm from W1AW, and could copy maybe 20 or 30% of that at best. So it came as something of a surprise, playing with Morsle for a few minutes, to discover I can do as well or better at 35 wpm as I can at 5.
You really get too much time at the slow speeds to engage the frontal cortex. If you learn to think your way to each letter, that doesn't scale very far.