I recall taking over a student who had flown eight hours dual in a Cessna 152. His instructor was away on holiday. We went to the aircraft and strapped in until he said he had left his checklist at home.
I said no problem just go ahead and scan the set up and start the engine. There was silence. "What the problem" says I?
"I don't know how to start the engine without the checklist" says the student "My instructor always told me to use the checklist and I don't know what to do."
I showed him the left to right scan. We got airborne. He flew quite well and did a credible landing. We parked. I waited for him to conduct the shut down. Silence. "Sorry, I have never shut down the engine without using a checklist to tell me what to do next." he said.
In eight hours he had never made a move without using a written checklist and his instructor was a Grade 2 who had been brought up from CPL training to always use a read and do checklist