That's known as a VR 4 schedule (variable-ratio 4) because the behavior is rewarded an average of every four times the correct response is given. Variable schedules maximize what is known as resistance to extinction; the probability a behavior will decrease in frequency goes down. Continuous schedules are best for establishing a new behavior. I would expect they use continuous reinforcement whenever a new skill is being learned in the game.
Upvote for content, but I think that there's a typo in your second sentence
Variable schedules maximize what is known as resistance to extinction, the probability a behavior will decrease in frequency goes down. Perhaps a semicolon instead of a comma, or "as frequency of rewards ... " instead of "in frequency ...", was intended?
http://measureofdoubt.com/2011/04/12/pulling-levers-killing-monsters-the-lure-of-unpredictable-rewards/ (how do I put a link like this in a word with blue letters?)
I've read that unpredictable rewards associated with a behavior actually encourage that behavior more effectively than consistent rewards.
The optimal habit-forming figure given in the link above is a 25% chance of reward for each instance of performing the behavior.
My hypothesis then, is that if I want to establish a habit by rewarding myself upon successfully performing a certain task, I should reward myself only 25% of the time if I want to ingrain the habit as forcefully as possible into my unconscious.
Anyone else think so, or have any other research to add?