London, July 4 Scientists studying postings on Twitter have put together a list of most laid-back celebrities on the popular microblogging website.

According to the study headed by Australian lager company Foster's, Jazz-pop singer Jamie Cullum was the most up-beat celebrity as per a scientific formula.

English comedian Jimmy Carr came in second, followed by British tennis star Andy Murray, reports The Telegraph.

American actress-singer Jessica Simpson grabbed the fourth spot, and wrapping up the top five was Leigh Francis, most famous for his comedy series Bo' Selecta! Most laid-back celebrities on June 30:

1. Jamie Cullum

2. Jimmy Carr

3. Andy Murray

4. Jessica Simpson

5. Leigh Francis (Bo Selecta!)

6. Chris Moyles

7. Jonathan Ross

8. Jamie Oliver

9. Sophie Ellis Bextor

10. Samantha Ronson (ANI)