New Delhi, Jan. 30 -- The marshmallow test, a social experiment at Stanford University in the 1960s and 1970s, made a comeback Thursday halfway across the world in New Delhi-in the Economic Survey penned by chief economic adviser Venkatramanan Anantha Nageswaran and team.

The test, credited to American psychologist Walter Mischel, was simple. Cohorts of four-year-olds at a pre-school on the sunny Stanford campus in California were given a marshmallow and two choices: they could have it immediately. Or, if a child waited for 15 minutes, she or he would get two marshmallows. The message: small reward now, bigger reward later.

The kids who were able to hold off for "delayed gratification" not only got more marshmallows, but when Mischel an...