McIlroy has a remarkable 800, 000 followers, meaning over one million people get to know the couple's inner thoughts and feelings every day.

CNN: Family first: Why Wozniacki is a winner

In a follow-up experiment they therefore asked 23 undergraduates who had romantic partners, and who stated that they prayed at least occasionally, either to pray for their partners daily for four weeks or to think positive thoughts about them every day for the same amount of time.

ECONOMIST: Praying for your partner stops you straying