Most of us would like something about ourselves or our lives to be different, but how easy is it to actually change?

Drs Chris and Xand van Tulleken are looking at whether people can change and how they do it. Exactly how much of any aspect of personality is genetic destiny and how much are we shaped by the world around us?

Chris wants to be a better doctor, friend, husband and father. But most urgently he wants to be a better brother, and is determined to improve his relationship with Xand. They’re best friends and talk to each other every day, but they are also business partners who find it very hard to work together without having a visceral row.

Chris wants to change how he relates to his brother and believes it is possible, but Xand is less convinced that we can or that he needs to change. In this series, Chris confronts that pessimism.

In episode 4 - Does Willpower Even Exist? - Chris examines the slippery concept of willpower. Is it something that we all need in order to make personal change and if so, can Chris harness it to encourage Xand to make changes in their relationship? Xand is preoccupied with his exercise bike which stands unused and dusty in his house, can he find the motivation to use it? The psychologist and psychoanalyst Dr Stephen Blumenthal explains willpower in the brain - when does and doesn’t it work?

Presented by Drs Chris and Xand van TullekenProduced by Hester Cant and Alexandra QuinnSeries Editor Jo RowntreeA Loftus Media and van Tulleken Brothers Ltd production for BBC Radio 4