that's the point, 2 is greater than 1, not 100x but still greater, would you choose greater benefit at the cost self gratification or short term gain?
The marginal utility of the second marshmallow is lower. Then there is added cost in the time spent waiting. Even if you have to wait in the room regardless, I think it’s fair to say there is a cost to delaying the gratification.
Why one extra? What if I just give you 5% of a marshmallow? 1%?
A coherent argument can be made that the extra costs are not worth it. I don’t particularly like marshmallows, but maybe I’ll eat one. Maybe two marshmallows in the future would be higher utility or whatnot than one marshmallow now, but that isn’t always the case.
What if I hold out for 10 minutes only to finally give in, and then the researcher returns seconds later? Better to fail fast than risk that.
At the moment there seems to be a lot of weight behind the idea that we only have so much willpower to burn in a day. So you might hold out against that tempting box of donuts all day at work, only to break down stop at a bar on the way home for a few pints.
I think on some level I've always felt that avoidance is better than fighting when it comes to willpower. First option - avoid the temptation. Second option - give in. Only if #1 isn't feasible and #2 is a very bad outcome, then go to battle.
There are multiple strategies people can take to willpower and life. Some work better than others in different situations.
There are people who don't mind waiting patiently for that 2nd marshmallow. I'm sure there are situations in life where that mindset is beneficial.
Move fast and break things is good for some goals, slow and steady is good for other goals.