A factor in this study that I don't know was mentioned in 'trust'. Did the kids trust the adult to deliver on the promise of the extra mashmallows. If the kids had low trust in adults, its very rational to take the marshmallow you see rather the ones you don't.
>In 2008–12, the rate of violent victimization was highest for persons in poor households (39.8 per 1,000) and lowest for persons in high-income households (16.9 per 1,000) (table 1). This pattern was consistent across all types of violent crime.
