There are those who can go cold turkey and others who simply can't kick the habit. Now researchers think they have discovered why some people just can't stop smoking – and it’s all to do with activity in the brain, The Daily Mail reports.

The U.S. scientists found they could predict how effective a reward-based quitting strategy would be in an individual by studying their brain activity.

The researchers observed the brains of nicotine-deprived smokers using MRI scans.

They found those who exhibited the weakest response to rewards were also the least willing to stop smoking, even when offered money to do so.

The researchers recruited 44 smokers to examine brain reward centre responses to monetary reward in those expecting to smoke and in those who were not, and the subsequent willingness of the smokers to forego a cigarette in an effort to earn more money.

The participants, who were between the ages of 18 and 45, all reported that they smoked at least 10 cigarettes per day for the past 12 months.

They were instructed to abstain from smoking and from using any products containing nicotine for 12 hours prior to arriving for the experiment.

The participants were informed that they would have to wait approximately two hours, until the experiment was over, to smoke a cigarette.

However, when the time came for the cigarette break, the participant was told that for every five minutes he or she did not smoke, he or she would receive $1 - with the potential to earn up to $10.