Money can buy happiness, research shows - but how much does it take?

The contentment comes from paying others to take on chores such as cleaning, cooking and gardening.

In this way, happiness can be bought in the form of free time, say scientists.

Psychology professor Elizabeth Dunn, from the University of British Columbia, Canada, co-led the study.

She said: "The benefits of buying time aren't just for wealthy people.

"We thought the effects might only hold up for people with quite a bit of disposable income, but to our surprise, we found the same effects across the income spectrum."

The scientists conducted a poll of 6,000 adults in the US, Canada, Denmark and the Netherlands.