Here is a related article on predicting student success which acknowledges the SAT and other contributory factors: http://growingleaders.com/blog/one-gigantic-predictor-success-students/

In recent discussions about the marshmallow experiment, several of us noted that other factors may be at play:
1) How well the subject may like a marshmallow. In a similar experiment, might students choose their own treat?
2) The degree to which students have developed a sense of trust in the powers-that-be. Might a separate survey be conducted to learn, for example, whether some parents may make promises and not follow through, perhaps counting on the child to "forget"?

These factors may continue to play out through out the student's life.
1) Do they like the idea of college (marshmallow)? Or would they be more motivated if they could choose their own treat?
2) Have others followed through on commitments (learning about and writing stellar recommendation letters, for example)?

In addition to measuring willingness to delay gratification, some of this seems to be about the student's perceived place in society: ability to be self-determining, and receive support.