Anthony is quite capable in all academic areas, although not particularly self-motivated. Usually, he doesn't care about his grades, but if there's a contest for the highest score on an assignment, he suddenly comes alive! Immediately, his habits change as he studies for hours and digs up all kinds of minor facts about the subject. This explains why he brought home a blue ribbon from the science fair, yet made a D on his regular schoolwork. Which signal word in the above paragraph contrasts Anthony's abilities with his willingness to study?

although
immediately
but
usually