Nerd note: the marshmallow test is heavily influenced by the child's socioeconomic environment as those who live with uncertainty of future security will reason that it's better to take what is available rather than gamble for what may be available.
"A bird in the hand is worth two in the bush"
Marshmallow Test
An experiment performed at Stanford University to measure the connection between the development of self-restraint at young age and success later in life.
The subjects were 4-year-old children chosen from the university's attached kindergarten.
In the experiment, the children were promised a second marshmallow on the condition that they kept from eating the one on the table for 15 minutes. The children were placed in a room with nothing but the table and a chair, and their self-restraint observed.