2 . If you examine the birth certificate of every soccer play in the last World Cup tournament, you will most likely find the excellent players were born in the earlier months of the year. If you then examine the European national youth teams that feed the World Cup, you will find this phenomenon even more ________.

What might account for this strange phenomenon? Some guess a certain astrological sign (星座) ________ superior soccer skills; others maintain that winter-born babies have higher oxygen capacity, which increases soccer stamina (耐力). But Anderson Ericsson, a 58-year-old professor who is called the expert on experts, believes in neither. His first experiment, nearly 30 years ago, involved ________: training a person to hear and repeat a random series of numbers. "With the first subject, after 20 hours of training, his digital span rose to 20", Ericsson recalls, "and after about 200 hours of training he could repeat up to 80 numbers."

This success, coupled with later research showing memory itself is not ________ determined, led Ericsson to conclude that the act of memorizing is a cognitive exercise, which means whatever inborn differences two people may exhibit in their abilities to memorize, those differences are ________ by how well each person encodes the information. And the best way to learn how to encode information meaningfully, Ericsson determined, was a process known as ________ practice. It involves more than simply repeating a task — playing a C-minor scale 100 times, ________, or hitting tennis serves until your shoulder pops out of its socket. ________, it involves stepping outside your comfort zone, setting specific and well-defined goals, focusing on ________ areas of expertise, obtaining immediate feedback from professionals and concentrating as much on technique as on outcome.

Ericsson and his colleagues have thus taken to studying high achievers in a wide range of ________, including soccer, golf, chess, piano playing and darts. They gather all the data they can and make a rather shocking statement: the trait we commonly call talent is highly ________. And yes, expert performers are nearly always made.

Ericsson's formula seems appealing to many tiger parents: "practice makes perfect" is naturally ________ to genetic determination. By ________ innate ability as insignificant, many are confident they can make a concert-level pianist or an Olympic figure skater of their kids as long as they push them hard enough. Ericsson, ________, believes what parents should learn from the science of expertise is not the effect of logging thousands of hours, but how to get kids to ________ the importance and challenge of effective practice.