The year was 2006, and for Dr Stephen Lea, a professor of psychology at the University of Exeter, the standard theory of money – that it’s simply a tool we 
use to obtain what we want – was no longer making sense.

Too many anomalies existed that the theory couldn’t explain. Why, for instance, did the allure of money so far exceed its evolutionary advantage? Why did we act as if having money was an end in itself, when its only real value came from exchange? And why was money always blinding us to our own best interests?

Suddenly Lea remembered an old experiment from his training days, conducted by 
a scientist named Schwab. He first asked people to hang from a pull-up bar as long as they could. Next they received the same instruction, along with verbal encouragement.

The third time, they received no encouragement; instead, they were shown and promised a small amount of cash to hang on longer than on their previous two tries. But on that third attempt, the people lasted about twice as long as they had in the first, and 50% longer than during the second. What could explain this difference in performance?

That’s when Lea began to wonder: what if money is a drug? Consider the evidence. The thought of money lights up the brain’s reward centres, as any stimulant might. 
Scientists have known this for a while. Money also actually changes the way we think. In studies from the University of Minnesota, researchers found that just seeing a picture of money jerked our brains into finance mode, ramping up our maths memory 
and priming us to keep our eyes on the prize. In fact, on a sluggish morning, the sight 
of a crisp one-hundred buck note can be as motivating as a blast of caffeine. In a 2006 experiment, for example, people reminded of money worked 70% longer at an assigned task than a control group did. And a follow-up study found that the effect extends to the social sphere, boosting our confidence and immunising us against the pain of rejection.