When a private in the Army gets so tired he just shuts down mentally and just follows orders without thinking. Also leads to NCOs noticing and fucking with private and he won't even realize he's being fucked with.
NCO: Private go ask the Specialist if he got the TR double E's that I told him to get for me.
Autoprivate: Yes Sergeant!
Specialist: Tell the Sergeant I put them by the ST 1s.
Autoprivate doesn't realize they had him looking for trees and stones.