From Utopia for Realists.

When you conatantly have to worry about having no money, you are stressed and it lowers your IQ by around 13 points.

In an experiment US mall shoppers were told that they had to fix their car and the bill for repairs was either $150 or $1,500. They were asked if they would pay the bill in full, get a loan, work overtime, or not make the repairs. While they were considering this, they were asked to perform cognative tests.

When the bill was $150 both high income and low income people scored the same in the cognative tests. When the bill was $1,500, low income people scored significantly lower than rich people in the cognative test. The idea of a ficticious high bill triggered their stress and caused them to make dumb decisions.

To check this experiment they ran a similar one in India with sugarcane farmers. They collect 60% of their income after the harvest, at which point they are "rich" (have money in their pocket), and towards the end of the year they are "poor". The results were repeated. With the exact same person they were dumb when money was a concern and smart when it wasn't.

This experiment disproves the belief of wealthy people that they are rich because they are smarter than poor people and therefore don't make stupid decisions.

Personally I recognise this behaviour in myself. As a relatively rich person, I will often make stupid decisions when even under minor stress. A small example; when I travel home from London late at night the trains are not that frequent. I try to avoid eating late at night. If I arrive at Waterloo and have to wait over 30 mins, I will eat junk food. Its a small example of what we'd euphamistically called weak will power due to tiredness for "successful" people. But it is no different to a poor person who is constantly struggling with money problems and decides to eat unhealthily, buy cigarettes they can't afford, or drink alcohol they also can't afford and consequently are hungover for work (or miss it).

Interestingly it's also an explanation for why in [universal basic income]( experiments, alcohol and cigarette spend goes down when you give people free money, contrary to popular opinion of what would happen.