Wednesday, February 28, 2018

Adolescents Get Fixated On Rewarding Things

It is common to talk about how the teenage years are a time of risky behavior.  And, when we talk about why teens engage in risky behavior, there is a tendency to focus on the development of the frontal lobes.  We know that there are mechanisms that involve the frontal lobes of the brain that stop behavior that has been engaged.  In Smart Change, I call these mechanisms the Stop System.  The frontal lobes do not mature fully until early adulthood, and so that is part of the reason why teens do risky things.
If it was just that the Stop System hasn’t matured yet, then even young children should engage in lots of risky behavior.  Instead, there is another component.  Adolescents also engage lots of behaviors that they perceive to be rewarding.  I call the mechanisms that drive people toward behaviors the Go System. 
This view suggests that adolescents have a perfect storm of a Go System that is driven to pursue rewards despite potential risks and a Stop System that is not capable of stopping a behavior that is risky.
An interesting paper in the November, 2014 issue of Psychological Science by Zachary Roper, Shaun Vecera, and Jatin Vaidya provides some evidence for this view of adolescent risky behavior.
These researchers suggest that if adolescents are drawn toward rewards, then they should persist in paying attention to rewarding items in the environment, even when they are no longer rewarding. 
To test this possibility, 40 teens (ranging in age from 13-16) and 40 adults (with an average age of 27) were run in a study.  In the first part of the study, participants saw a number of colored circles on a computer screen.  Inside of each circle was a line.  There was always one red or green circle on the screen, and the rest were other colors.  Participants had to press one of two buttons to indicate whether the line inside the target circle was horizontal or vertical.  When they responded correctly, they were rewarded.  For each participant, one color was generally associated with a larger reward (10 cents) than the other (2 cents).  So, for a particular participant, the red circle might generally lead to a 10 cent reward and the green circle might lead to a 2 cent reward.
After doing 240 trials like this, the task was changed.  Now, participants did another 240 trials in which they had to find a blue diamond and report the orientation of the line inside that shape.  The rest of the objects on the screen during these test trials (which are called distractor items) were colored circles.  On some trials, one of those distractor circles was a red or green, which had been associated with a reward in the first part of the study. 
The key question was whether the amount of time it took participants to respond correctly on the test trials was affected by the presence of circles that had been rewarded in the first part of the study.  If it takes longer for participants to respond in the presence of a distractor that had been rewarded in the past, it suggests that distractor is attracting attention from the real goal of the task.
Adults are not strongly affected by the initial training.  In the first group of test trials, they are a little slower at responding when one of the distractors had been rewarded in the first group of trials.  After about 60 trials, though, adults are no longer affected by what had been rewarded before.  That is, the Go System no longer drives adults toward old rewards.
The teens act quite differently.  They are much slower to respond when one of the distracting circles had been rewarded in the past.   They are slowest when the distractor was color that got the large reward.  They are fastest when none of the distractors had been rewarded.  The circle that got the small reward came out in between.  This effect persisted over the entire set of 240 test trials.
Finally, the effect was strongest in the 13- and 14-year-olds who were tested.  They were most captivated by the circles that had been rewarded before.  The 15- and 16-year olds were also a bit slower when faced with a circle that had been rewarded before, but not as much as the younger teens.
This suggests that the risky behavior we see in teens has two sources.  First, the Go System of teens gets directed toward things that have been rewarded in the past.  It is hard for teens to dampen this activity of the Go System.  Then, on top of that, the Stop System has trouble overcoming the direction of the Go System, so that teens continue to act on the impulse to do what had been rewarded on the past. 
Ultimately, this validates the importance of using the environment to help teens protect themselves.  It is just hard for teens to overcome strong temptations.  Perhaps the best way to help teens to avoid risky behavior is to remove the most significant risks from the environment.  While teens have to learn to say no to activities they should not perform, there is no reason for them to have to overcome the full strength of their Go Systems.

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