Parents who say they don't play favourites with their children are obviously lying or fooling themselves.
According to an October issue of Time magazine, our brains are hardwired to do so.
"Nature impels us to have to have a favourite child," said journalist and author Jeffery Kleuger.
Typically the oldest child is favoured because of "the idea of sunk costs".
"You've invested more time, money, resources, even calories into the first born," said eldest child Kleuger.
For Elisabeth Röhm, best known for her role as Serena Southerlyn on Law & Order, one is a very lonely number.
