Attention, memory and perception
Serial position effect
Also called Primacy and recency effects
People remember the first and last items in a list best, and the middle ones least.
Early items get more attention and rehearsal (primacy), and the last ones are still fresh (recency). The middle blurs.
Put the most important options at the start and end of a list or navigation bar, and the least important in the middle.
In practice
A mobile tab bar with Home first and the account at the end, the two places people look for them.
Common mistake
Leaning on position alone. A long list stays hard to use whatever order it's in; shorten it or group it first.
Where it comes from
Hermann Ebbinghaus noted the pattern in his memory experiments of 1885, and Bennet Murdock measured the classic curve in 1962.