One reward was financial - subjects played a card game and were rewarded with money for winning.
The second was reputational - subjects were shown a picture of their face with a positive or negative description underneath, supposedly written by their peers. When the subject’s brain was monitored it showed that the brain responded in exactly the same way to the financial reward as it did to positive reputation.

I think this goes some way in explaining the 'double' addiction to Steemit!