NYTimes: ... People who accomplished great things, she noticed, often combined a passion for a single mission with an unswerving dedication to achieve that mission, whatever the obstacles and however long it might take. She decided she needed to name this quality, and she chose the word “grit.”
She developed a test to measure grit, which she called the Grit Scale. It is a deceptively simple test, in that it requires you to rate yourself on just 12 questions, from “I finish whatever I begin” to “I often set a goal but later choose to pursue a different one.” It takes about three minutes to complete, and it relies entirely on self-report — and yet when Duckworth took it out into the field, she found it was remarkably predictive of success. At Penn, high grit ratings allowed students with relatively low college-board scores to nonetheless achieve high G.P.A.’s. Duckworth and her collaborators gave their grit test to more than 1,200 freshman cadets as they entered West Point and embarked on the grueling summer training course known as Beast Barracks. The military has developed its own complex evaluation, called the Whole Candidate Score, to judge incoming cadets and predict which of them will survive the demands of West Point; it includes academic grades, a gauge of physical fitness and a Leadership Potential Score. But at the end of Beast Barracks, the more accurate predictor of which cadets persisted and which ones dropped out turned out to be Duckworth’s 12-item grit questionnaire.
[Of course, the grit score can't be used for admissions -- too easy to game, unlike an IQ test! Instead we use proxies for grit, like extracurriculars.]
... The first question Duckworth addressed, again, was the relative importance of I.Q. and self-control. She and her team of researchers gave middle-school students at Riverdale and KIPP a variety of psychological and I.Q. tests. They found that at both schools, I.Q. was the better predictor of scores on statewide achievement tests, but measures of self-control were more reliable indicators of report-card grades.
Duckworth’s research convinced Levin and Randolph that they should try to foster self-control and grit in their students. Yet those didn’t seem like the only character strengths that mattered. ... After a few small adjustments (Levin and Randolph opted to drop love in favor of curiosity), they settled on a final list: zest, grit, self-control, social intelligence, gratitude, optimism and curiosity.
Here's a figure from our paper Data Mining the University, which shows how SAT predicts GPA. The stars are over- and under-achievers (blue = male, red = female). Do the people in the upper left (over-achievers) have grit?