Motivation and habit
Goal gradient effect
People speed up as they get closer to a goal, and even the feeling of progress made for them can get them started.
Motivation isn't flat across a task. The nearer the finish looks, the harder people push, which is why the last few steps of a checklist go faster than the first.
In a product, show progress clearly and start people off with some of it already done. A profile that opens at 20% complete gets finished more often than one that opens at zero, because the goal already feels within reach.
In practice
A coffee card that needs twelve stamps and comes with two already stamped gets completed faster than a card that needs ten, even though the work left is the same.
Common mistake
Faking progress, or moving the finish line once people are close. It works once, and then people stop believing your progress bars.
Where it comes from
Clark Hull described the goal gradient in 1932, from rats running faster as they neared food at the end of a maze. Ran Kivetz, Oleg Urminsky and Yuhuang Zheng showed it in people with coffee loyalty cards in 2006.