Jakob loves to run because he feels so fantastic afterward. In fact, whenever he wants a runner's high—that feeling of elation after a lengthy run—he has learned to go for eight laps around the high school track. Jakob keeps this habit up for years because he likes the outcome he gets each time. What does this demonstrate?

Jakob has good stamina and endurance.
Jakob is operantly conditioned.
Jakob opens himself up to punishment.
none of the above