Sometimes our brains compel us to repeat choices that are neither productive or rewarding - a subject of interest to Professor Trevor Robbins at the University of Cambridge. For example, he has shown that rats with a lower than usual number of dopamine receptors in their brains are at risk for cocaine addiction. Those rats self-administer cocaine to the exclusion of other activities, and despite adverse consequences - two classic criteria of addiction. His work suggests that humans with low dopamine receptors may also be susceptible to addiction.

People with obsessive-compulsive disorder (OCD) - a notoriously intractable disorder - similarly experience a difficulty in stopping certain behaviours. fMRI and structural imaging studies showed that the parts of the frontal cortex associated with flexibility and inhibition control were under-activated in these people, and they also had significantly decreased grey matter in those areas compared with healthy controls. 

An exciting result was that first-degree relatives of these patients, although they did not have any behavioural symptoms of OCD, showed the same inflexibility on the same tasks - and the under-activations and decreased grey matter in the cortex. This suggests OCD may be an endophenotype, a cognitive problem in the genes of this family.

Professor Stephen Williams at the Institute of Psychiatry (IoP) at King's College London and colleagues have devised new methods that are making it possible to diagnose psychiatric disorders such as autism, schizophrenia, Alzheimer's ADHD and addiction with 85-90 per cent accuracy - and to tell whether a patient is likely to respond to specific treatments.

Not only will this save patients months of wasted time, misery and frustration as they wait to see if a particular medication or treatment works for them - it also  removes stigma around psychiatric illness by objectifying it in a brain scan. 

Addiction, OCD, autism, schizophrenia and impulsivity are all disorders that, untreated, have a very powerful effect on our thoughts, choices and actions - and neuroscience is showing us the roots of that effect in the sometimes overwhelmingly compelling workings of the brain.

As is the case with our genes, it appears our brains give us certain predispositions. Some of these are absolute and inescapable. And some of them we can change - through our choices, behaviours and sometimes through medical intervention, as we shape ourselves over the course of our lives.