The mind of a child has a much simpler thought process.When you expose them to a test, it is less likely for them to think too much into it where adults might even try to break or game the test. Testing someone at a your age can result in actions that closely resemble the inborn instinct of an individual. Stanford marshmallow experiment is one such experiment.

A 2018 study by Tyler W. Watts, Greg J. Duncan and Haonan Quan revealed that by the time the kids reach age 15, the marshmallow experiment becomes less useful.

We replicated and extended Shoda, Mischel, and Peake’s (1990) famous marshmallow study, which showed strong bivariate correlations between a child’s ability to delay gratification just before entering school and both adolescent achievement and socioemotional behaviors. Concentrating on children whose mothers had not completed college, we found that an additional minute waited at age 4 predicted a gain of approximately one tenth of a standard deviation in achievement at age 15. But this bivariate correlation was only half the size of those reported in the original studies and was reduced by two thirds in the presence of controls for family background, early cognitive ability, and the home environment. Most of the variation in adolescent achievement came from being able to wait at least 20 s. Associations between delay time and measures of behavioral outcomes at age 15 were much smaller and rarely statistically significant.
Full Research Paper At: http://journals.sagepub.com/doi/10.1177/0956797618761661

Why?

Individuals grow and become more capable. Walking 2 miles could be a big deal for a 4 year old. But even 5 miles isn't that huge for an adult. A dollar is barely worth anything for someone living in a first world country. But for someone in Venezuela, few dollars is all they earn in a whole month if they are lucky. Maybe the marshmallow was a little too little for the teenagers. Maybe an iPhone would have done the trick. Maybe the waiting time was too small. People become more patient and disciplined when they grow, so 15 minutes could be something small for them. Maybe the teenagers have been deceived in their life and they are less likely to expect people to keep their promises.

But one thing is clear. It's easier to measure and influence a very young child.

The Economic Implications

@jaichai actually made a great post titled Pillars Or Pariahs: Is Your Diet, Daily Routine And Mindset Helping or Hindering Your Willpower? which you should all check out. There were lots of great content in the post.

It is common Austrian wisdom that to really build wealth you need to consume less than you produce and invest the saved difference to create a positive sum game. If I pick an easier to relate example, I'd say look at STEEM blockchain. Like any other social media, you'll have to wait and build you followers and portfolio of content. Even if you are one of the greatest writers on the planet, you won't get that much recognition at the beginning. An year ago I was a tiny plankton with a tiny reputation earning barely nothing. Now I'm managing to earn few dollars everyday as a result of my hard work. I've manage to rank among the 1% under many metrics and when it comes to reputation I'm sort of on the Top 500. That's after a whole year on the blockchain.

Some people have done way better. But even they had to put some serious effort. Then they had to wait. If you have done any trading, you'll know that you have to play a very long and patient game. Personally I think learning to become a good trader can give more discipline to a person in a very efficient way far better than any military ever could.

Imagine A World With No Long Term Vision

Actually you don't have to. The cavemen and even those who lived in middle ages lived only thinking about the day or at best the next year or two. Except for building some places like castles, fortresses etc. there wasn't much of a vision for the future. On important fact is that the children of less fortunate households/communities are the ones who are most averse to delayed gratification. This is practically creating sort of a death spiral. Without making intelligent bets on a future, they just decide things for the short term. The result: there future is going to suck even more.

The Curse of Voting and Elections

One head one vote system creates a distortion of reality where anyone's genius is equal to another's stupidity. If an election is going to happen every 4 years, there is no guarantee that a project can be carried out for longer than 4 years. If people don't see a reason to vote someone to gain something in the next 4 years, they are less likely to vote for that long term planner.

The worst part is that based on the theory of combining The Stanford Marshmallow Experiment and Democracy, we'll have to say that the worse of a country is, more destruction is caused by democracy. I'd say empirical evidence is actually in favor of this. Take a look at India for an example. "Corruption" is actually expected part of the daily routine. At least in developed countries nobody needs to be sucking off to or outright bribe politicians to get some basic hings done.

How Dubai Became Dubai

Dubai is one of the greatest examples of long term self-interested planning bringing prosperity. Most other aspects are controlled. The only resource Dubai had was some Oil (nothing huge like Venezuela did) and that's about it. It was a dessert with Sharia Law which is not a very sensible code to live by. I'd actually say that Sharia Law halts progress than help it. Dubai grew based on entrepreneurship and long term vision. There was no voting involved.

DPoS - Voting With Stake To Grow your Stake

STEEM asks you to lock your funds for 13 weeks if you want to vote on decisions. This is a right way to practice voting. You can change your vote every 3 seconds. This time frame is too small for anyone to focus on the short term. The witnesses try to do things that count for the long term because of the voters see witnesses doing something unfavorable to their investments, voters could simply change the vote. So the game plan for a witness naturally becomes that of a reputation building.

A reputation takes forever to build and a moment to loose.

Those who ask for witness votes have to be willing to build a future than reap the benefits. But how can this be translated to the real world? I have an answer and I almost typed it. But instead I'm going to ask you thoughts. So work your brains and try to come up with a governance system for the real world that allows or favors delayed gratification.

Good Luck!