We all think we have control of our actions but if a brain tumour or injury can completely change our personality, what does that tell us about free will, asks David Edmonds.

Go to the gym or sit in front of the telly with a family-sized packet of crisps? Hmm. Gym or crisps? Gym or crisps? Gym or crisps?

Well, we’ve all been there. We may decide that what we really want to do is go to the gym – yet find ourselves reaching for that tasty salt-and-vinegar snack, followed by the inevitable feelings of self-loathing.

Neuroscientists and psychologists are making tremendous strides in understanding our drives and motivations. Weakness of will – eating those crisps when we don’t really want to – is one intriguing phenomenon. Another is addiction, whether it be to gambling, sex, booze or cigarettes. Much is being learnt about the physiological mechanisms that underlie our compulsive appetites.

There’s a growing recognition of the importance of the subconscious in our decision-making. We may not even be aware of the influence that a surrounding smell or noise is having on our choices. And some neuroscientists have even claimed that by examining patterns in the brain, they can predict decisions that we will take six or seven seconds before we ourselves consciously choose to take them.

​Click to read​