A study was done on adopted siblings being raised in the same household. These adopted siblings are not genetically related.
Which of the following pieces of evidence would lend the greatest support to Scientist 1’s argument?
The Root of Addiction
Addiction is a behavioral disorder in which an individual is unable to control impulses for an immediately rewarding
stimulus, regardless of the long-term or delayed consequences. Most addiction stems from the same reward
systems in our brain that let us know that an apple is good. When we eat an apple (or any high-sugar substance), our
brain rewards us for finding a good source of energy with a pleasurable feeling by releasing the chemical
neurotransmitter dopamine, which causes the physiological ‘good’ feeling. This likely evolved to ensure that our
ancestors sought out and ate foods that would meet the energy demands of their bodies. Research has shown that
this reward system is also set off by various, non-beneficial stimuli as well. For instance, nicotine, the addictive
substance in cigarettes, triggers the reward pathway of the brain, giving smokers a ‘good’ and relaxed feeling. As a
smoker’s brain becomes accustomed to the nicotine stimulus, it starts to ‘expect’ more of it. As a result of the brain’s
conditioning, a decrease in the stimulus results in unpleasant withdrawal symptoms. At this point, the individual is
The behavior of addiction stems from environmental experiences and conditioning. Addiction is the product of one’s
surroundings and experiences, especially as a youth. For instance, over 50% of children who drink regularly (once
per week) before the age of 14 become alcoholics. In fact, in most addictions, anytime an addictive substance is
regularly available to teens and pre-teens, their likelihood of becoming addicted is substantially increased. Another
environmental influence seems to be the emotional support system an individual. When surveyed addicts are 65%
more likely to report feeling a lack of emotional support compared to the non-addict population. Addicts also are
typically unable to name adults they trusted growing up. What all of this suggests is that one’s upbringing and
experience plays a crucial role in the probability of developing an addiction.
The human reward pathway works in the same way a dog learns to associate a behavior, such as sitting, with a treat.
Even if that treat is unhealthy for the dog and could lead to obesity or some other issue, the dog will still sit when
offered the treat. What humans are typically capable of doing is using their brain’s highly evolved frontal lobe (which
separates us from other animals) to resist the impulse of acting on an immediate reward, due to foreseeable future
consequences. Most research agrees that stressful upbringing decreases a child’s frontal lobe development, and
reduces their ability to predict future negative outcomes, and their ability to resist impulse. An addict associates
their addiction with a rewarding feeling without regard for the possible side effects.
As such, addiction can be treated and cured with behavior modification techniques that teach the addict to associate
their addiction with negative consequences. For instance, imagine if cigarettes caused the subject stomach cramps
and nausea. After a few days of such displeasure, the addict would begin to associate cigarettes with the negative
consequences, and no longer crave a smoke.
While environmental influences may be necessary, addiction is clearly genetically based. For some individuals,
trying cigarettes in childhood is enough to create a full-blown addiction. These individuals have also been shown to
be more likely to become easily addicted to other drugs and/or potentially hazardous activities. Why? What makes
one person more likely to quickly develop an addiction, while another requires a far greater quantity of the stimulus
to develop the same addiction?
The answer seems to lie in the brain cells, more specifically, in their genes. It has long been thought that addiction
runs in families. Some behaviorists have speculated that this is due solely to the fact that these individuals are raised
together, or in similar environments. However, studies on identical twins separated at birth have repeatedly shown
that two genetically identical individuals, brought up in completely different environments, have the same likelihood
of suffering from addiction. In 94% of cases where one identical twin suffered from drug addiction, the other twin
did as well.
What does this mean for treating addiction? This seems in line with many addiction support groups that claim one is
never cured of addiction. Without altering the genes of the cells involved, it is unlikely that addiction could be
definitively cured. But treatments are available. Most treatments involve behavioral modification programs,
therapy, and support groups. Although they cannot cure an addict, they may be able to help the individual resist his
or her addiction.