A study of expert and novice 10 year-old soccer players is conducted over 6 weeks. findings reveal that at the end of the season, game performance improved. if this study is similar to one by french and thomas (1987) about basketball game play, the primary contributor to improvement would be

I believe the answer is: players' ability to make more appropriate cognitive decisions during the game

The novice players tend to gain this ability after observing how the experts above them play and through the accumulation of experience that they do throughout the games. The players' cognitive abiltiy would keep developing until they hit the age where both their brain and physical function start to experiencing impairment.