R. Douglas Fields, in his recent blog post, reports on an interesting study by Hofer et al, that shows a sort of dissociation between the effects of cognitive ability (intelligence) and personality attributes (self-control) when it came to academic achievement.
Academic success was assessed by two measures: self-reported grades and a score on a math achievement test, in a study of 697 German eighth graders. The researchers found that cognitive ability was related to the math achievement score, while the personality factor of self-control was related to good grades.
Fields takes that to deduce that learning depends on cognitive ability (he claims that the achievement test measures transfer of learning from one domain to other) while good grades depend on hard work — the ability to keep churning on assignments at required times, due to one's better ability to control oneself.
I believe Fields is making an unjustified leap here. Equating test scores with learning is doubtful to me. Cognitive ability yes, but learning a little doubtful. Intelligence, or innate ability, may help you ace a test, by making you focus narrowly on performance goals, but they are no good at making you really learn; as a matter of fact, research by Carol Dweck has shown that performance and learning/mastery goals are at times antithetical to each other. Of course, if the given test in question, did measure transfer of learning, it was probably tapping into another important construct- the growth/fixed mindset which would either enable or disable a child to really learn and then transfer learning to novel contexts.
Similarly, a good grade, which is a cumulative result of how you behave and perform throughout the year, is equally dependent on your ability to self-regulate and self-control yourself—which results in hard work—as it is on your motivational level or goal strength—which results in resilience and persistence in face of setbacks. That is not to say that cognitive ability or mindset will not have some impact.
Thus I would suggest that all academic success, however they are measured, are dependent on four factors: innate ability or intelligence, self-control and hard work, grit and motivational resilience and finally, a positive, incremental mindset. While some academic outcomes, like achievement test results (e.g., SATs) may depend disproportionately on innate ability and mindset (test results and transfer of learning), other outcomes—like grades—may depend more on personality factors like self-control and grit/motivation.
However, to assert that good grades tell you only about personality/character and high test scores tell you only about ability/mindset, is an incomplete picture of the academic future or life-outcomes of a person. To be really able to predict how that person will do in life/academics, one needs to factor in grades, scores, and perhaps add to the mixture recommendations from a teacher/ guide who has observed the person closely. That's exactly what graduate schools use for their admission processes.
Hofer, M., Kuhnle, C., Kilian, B., and Fries, S. (2012) Cognitive ability and personality variables as predictors of school grades and test scores in adolescents. Learning and Instruction 22, 368-75.