Addictive personality may be hard-wired in the brain
By William Smith
What makes some individuals become addicts whilst others seem to be able to take or leave substances such as tobacco, alcohol, drugs and food?
Determining why some people, but not others, succumb to these substances has been an area of investigation for some years.
One previous study was conducted in the late 1960s and early l970s. This study used marshmallows and biscuits to assess the ability of preschool children to delay gratification. If they resisted the temptation to eat a treat they were then rewarded with more treats later. Some children held off on the temptation whilst others did not.
Now, some 40 years later, researchers revisited some of the same children and find that the differences still remain. The children who were better at delaying gratification remained the same in adulthood. Similarly, those who wanted their biscuits ‘now’ as children were more likely to want instant gratification as adults.
Brain imaging supported this discovery. It showed key differences between the two groups in tow areas, the prefrontal cortex and the ventral striatum.
The lead author, B. J. Casey, Ph.D., said ‘This is the first time we have located the specific brain areas related to delayed gratification. This could have major implications in the treatment of obesity and addictions.’
The findings are published in the Proceedings of the National Academy of Sciences.
For the current study, Casey and her co-researchers recruited 59 adults who had participated as children in the original study. The participants represented either extreme or delayed-gratification – high delayers or low delayers.
Marshmallows and biscuits are less appealing to adults so the researchers used two alternative tests.
In the first test the participants looked at a screen displaying a series of faces and were asked to signal only when a face of one gender was shown. This test revealed no significant differences between the two groups. This test was classed as a ‘cool’ test.
The second test was a ‘hot’ test which used emotional cues such as happy or frightened faces. In this test the results were varied and consistent with the childhood grouping of individuals responding to immediate as opposed to delayed gratification.
‘In this test, a happy face took the place of the marshmallow. The positive social cue interfered with the low delayer’s ability to suppress his or her actions,’ said Casey.
The second test was then repeated while the participant’s brain was scanned using functional magnet resonance imaging (fMRI).
The results showed that the brain’s prefrontal cortex was more active for high delayers and the ventral striatum, an area linked to addictions, was more active in low delayers.
Source: Cornell University
