The researchers observed the brains of nicotine-deprived smokers with functional magnetic resonance imaging (fMRI) and found that those who exhibited the weakest response to rewards were also the least willing to refrain from smoking, even when offered money to do so.
"We believe that our findings may help to explain why some smokers find it so difficult to quit smoking," Stephen J. Wilson, assistant professor of psychology, Penn State said.
"Namely, potential sources of reinforcement for giving up smoking -- for example, the prospect of saving money or improving health -- may hold less value for some individuals and, accordingly, have less impact on their behavior," he said.
The researchers recruited 44 smokers to examine striatal response 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 striatum is part of the so-called reward system in the brain," Wilson said.
"It is the area of the brain that is important for motivation and goal-directed behavior -- functions highly relevant to addiction," he said.
Wilson and his colleagues reported that they found that smokers who could not resist the temptation to smoke also showed weaker responses in the ventral striatum when offered monetary rewards while in the fMRI.
The study is published in the journal Cognitive, Affective and Behavioral Neuroscience.