This problem often begins with a distraction that causes fixation on an instrument or occurrence. Complex flight operations are the first skills to deteriorate.
Silence prevails
Seat posture relaxes
Bad judgment prevails
Instruments are ignored
Attention and vision fixates
Eye/hand skills begin to fail
Writing becomes less linear
Heading excursions take place
Movements decrease and slow
Clearances cannot be copied in total
Knowing where you are becomes a problem
Pilot accepts what exists as O.K. without checking
External references begin to fade from consciousness