Black Friday: why our brains love a bargain

Do you prefer Black Friday or Cyber Monday? The January sales or Amazon's Prime Day? Or perhaps you like to hold out for a good old fashioned everything-must-go shop clearance.

For whatever your shopping habits, there's a good chance that you like the idea of bagging a bargain.

The days and weeks before Black Friday reflect this feverish appetite. You can't look anywhere online without being bombarded with adverts and offers of supposedly special deals in the run up to Christmas.

And bricks-and-mortar retailers love putting on a sale too. Joining a long queue of fellow ...