Adolescence. Nature’s way of preparing parents to welcome an empty nest. Throughout my time as a teacher, I was always fascinated and amused in equal measure by the many paradoxes of the period; a time when we are somehow both at our strongest and at our most vulnerable. It is also, of course, a period with a bad reputation, bemoaned by the Ancient Greeks, Romans and myriad commentators since. The reason for this isn’t perhaps as obvious as it might at first appear. It can’t just be the result of inadequacies on the part of the adolescents; younger children are able to do far less and we don’t share the same degree of frustration at their limitations. The stereotypical and historic frustration with adolescents presumably comes instead from a mismatch between our expectations for their behaviour and the reality; they fall short of the standards that we often set them.
Why is this? What leads to this discrepancy between expectations and behaviour? I think that there are three factors at play here. Firstly, and perhaps most obviously, adolescents are increasingly adult in appearance, so this superficial physical resemblance may lead us to expect that they will also behave like adults. Secondly, the consequences of adolescent shortcomings have the potential to be much more serious than for younger children. Adolescents are given a greater degree of freedom to explore their environment than younger children, and so have a much greater scope to display risky behaviours and find themselves in perilous situations. This explains why adolescents are consistently at the top of the ‘accidental deaths by age’ charts1. The third reason, however, is the most interesting from a psychological and neuroscientific perspective (as well as being probably the most frustrating for parents and teachers everywhere). This is that we know that teenagers CAN produce the behaviours that we would like them to; they just don’t (at least, they don’t all the time). We see that under certain circumstances they are able to act very successfully in what we might call an ‘adult’ manner: making decisions calmly, rationally and even diligently. The frustration, then, comes when this is not repeated in other situations.
I want to take a closer look at this third point in this post, focusing specifically on attention (my current area of study), to try to explain why an adolescent brain may act in an ‘adult’ way some of the time, but in a decidedly ‘teenage’ or even childish way at others.
They can do it, but don’t always
The majority of the staggeringly clever processes that our brain is able to perform are up and running well before adolescence. Our sensory systems, which are able to selectively process and interact with information from our environment more effectively than the most expensive supercomputer, are pretty much fully developed by the age of 9. Even more complex and later developing abilities associated with adult thinking, such as the so-called ‘executive functions’ (EFs) are in many cases developed by early adolescence2. EFs are typically divided into three key components; inhibition (being able to inhibit what might be a reflexive or habitual response in favour of a different one), working memory (being able to hold and manipulate information in our minds) and flexibility (being able to approach a problem flexibly from different angles). For all these three components, we are able to find particular tests and experiments where by age 14 or so performance is typically approaching adult levels3, 4. Seemingly adolescents do possess the skills to perform these tasks successfully in some situations… so why not all the time?
One way to try to answer this question is to look at the teenage brain itself, and its development over this period. We can very clearly see from brain imaging studies that there is still a great deal of change occurring in the adolescent brain5. Indeed, the reorganisation and development of the brain continues at least into the mid-twenties, if not even longer. If we look at the specific areas of the brain which are developing through adolescence, the main area of change seems to be in the frontal lobe.
This fits with the behavioural evidence, as this is a part of the brain which seems to play a large role in controlling our executive functions. The frontal lobe is in charge of “doing the harder thing” to quote Robert Sapolsky. Any time that you need to inhibit your usual behaviour, to ignore or put off something that would be more interesting than what you’re currently doing or to think really hard about something, it’s likely that your frontal lobe is central to that process. It would seem odd then, if such development at a neural level were not reflected in some way in behaviour; suggesting that even if 14-15 year olds can perform at adult levels in some EF tasks, there are likely to be other tasks that they might find more difficult. This ability to do some tasks but not others might then help to provide us with an explanation for the classic behavioural inconsistencies which are the staple of forums on Mumsnet. But to understand why this is in more detail we need to look at the specific effects of trying to make decisions with a frontal lobe that’s developing more slowly than the rest of the brain.
Three insights from psychological and neuroscientific research which can help to explain why teenagers can do it, but not always:
- Some things are disproportionately distracting for teenagers.
- It’s harder work for them to make careful decisions
- They don’t learn from the environment quite as effectively as adults, so it’s harder to work out when to produce certain behaviours.
- Emotion and Reward: Master Distractors
As mentioned above, teenagers can do certain types of task very well. As an example, let’s take a simple test of inhibition and attention, commonly used in research: the ‘flanker task’. The flanker task asks participants to identify a central target (for example the direction that an arrow is pointing), and to ignore the ‘flankers’, (other stimuli, for example other arrows). Although they may try their best to ignore them, participants are generally faster at identifying the direction of the central arrow if the flanker arrows are pointing the same way (a ‘congruent’ trial) than if they are pointing the opposite way (an ‘incongruent’ trial – see the picture of the standard flanker task on the left below).
Performance on standard flanker tasks generally reaches adult levels by mid-adolescence (age 14 or so)7. The same pattern holds with other tests of inhibition such as the anti-saccade task (where participants are trained to look away from a cue, rather than towards it; e.g. ‘if the target appears on the left, look right’)8.
However, when researchers try variations on these types of task, the results are less clear-cut. Take a look at the ‘emotional flanker task’ picture on the right above. The basic idea here is exactly the same as the traditional flanker task; the participant just has to identify the expression in the middle (either ‘fear’ or ‘happy’), whilst ignoring the faces either side. In this modified task, however, even older adolescents (15-19 year olds) have been found to be less accurate than adults9. They also took longer than adults to respond when there were ‘fear’ faces as flankers to a happy face, suggesting that the teenagers were finding it harder to ignore these emotionally-charged pictures. Emotional distraction of older teenagers has been observed using other types of task as well, suggesting that it is not limited to flanker tasks10. In one study of matching emotion words (‘happy’, ‘sad’ or ‘fear’) to pictures of faces showing these emotions, performance in adolescence dipped below that of younger children and did not return to pre-pubescent levels until age 16-1718. Similar sorts of results have been found for reward. Adolescents seem to have an increased sensitivity to rewards; compared to adults, they are more distracted by pictures which have previously been associated with a reward (but which aren’t anymore)11. One study found an increased response to reward in adolescent brains compared to adults, a state which occurred just before they were about to make their response in the task. This exaggerated response to reward whilst they are in the process of choosing the right action to perform may make adolescents vulnerable to making impulsive or poor decisions12. It may also explain why adolescents seem happier than adults to embrace ambiguous situations, where the potential for reward or harm is unclear20.
From an evolutionary perspective, it makes sense that things associated with emotion and reward should be especially good at capturing the attention of adolescents. As they begin to seek out the skills required for an independent adult existence, adolescents require new experiences from as many different situations as possible. As a result they begin to show ‘sensation seeking’ behaviours, ones designed to prioritise the novel and the stimulating (this has been reported across many other mammal species as well as humans)13. Both emotional and rewarding stimuli are clearly likely to be preferred in a period of ‘sensation seeking’, hence why they seem to produce more distracting influences on adolescent behaviour than on other age groups14. We also know that parts of the brain important for the processing of emotion, motivation and reward, such as the amygdala (see picture above), tend to mature before the frontal lobe. This may create an imbalance where we have developed strong responses to some stimuli (through the amygdala), but not developed the tools to control these responses adequately (through the frontal lobe)14.
2. I can’t – it’s too hard!
Studies which have looked at the activity in the brain during EF tasks have found that, even if they are producing similar results, there are differences in how hard adolescent and adult brains have to work to get there. Adolescent brains show higher activity levels than adults when asked to inhibit habitual responses, suggesting that engaging EFs requires greater engagement and mental effort for them than it does for adults15. At the same time, other networks in the brain which are associated with being in a general state of concentration and focus, show less activity in adolescents during experiments than in adults, suggesting that they find it harder to maintain a focused state which will facilitate accurate responding and ignoring distractions16. Indeed, this fits with the self-reports of adolescents, who report a greater vulnerability to external distraction than do young adults6. Taken together, these two findings suggest that although adolescents may be able to produce adult levels of performance, it is likely to be more challenging and tiring for them to do so consistently.
- They just don’t learn, do they?!
There is also some interesting recent evidence to suggest that, in addition to the points above, adolescents may not learn from the environment quite as effectively as other age groups. In the context of ‘sensation seeking’, when the drive for new experiences is very high, it has been argued that effective learning can only occur after similarly high levels of reward17. In other words, small levels of feedback which might be more than enough for an adult to adjust their behaviour, are not likely to register with adolescents in the same way. Praising your teenager for behaving well one week may only increase your bafflement when totally different behaviour is displayed in a similar situation the next, but it may just be that the feedback was not powerful or salient enough to break through into real learning. In the same way, this may explain the pattern of making the same mistakes repeatedly!
A final thought: the real world is more complicated than these tests!
We have seen that in many experimental tasks, adolescents are capable of adult levels of performance by around the age of 14, but that they may have to work harder to produce these levels, and variations on these tasks which introduce other elements such as reward or an emotional aspect can significantly impair this. One final thing to bear in mind is that, of course, in the real world the problems tend to be a lot more complex than the lab. Ultimately, most of the studies above only address a single measure of executive function, perhaps with one specific type of distractor thrown in. Naturally, impulsive decisions and actions taken by adolescents in their day-to-day lives are governed by more complex and nuanced mechanisms than those that govern performance of these tasks, with emotional content, rewards, memory demands and more all operating simultaneously. We should expect, then, that in the real world this development might be more delayed than for the simpler laboratory tasks. Indeed, some studies investigating more complex combinations of EFs (such as guessing the rules that have been used to sort a stack of cards) have found dips in performance up to 18 years of age, though these findings need to be replicated and investigated in more detail19.
There is still a lot that we don’t know about how adolescents are able to control their thoughts and attention, and what features of stimuli may be particularly distracting to them at different times. Most of the current research uses ‘distractors’ that are somehow related to the task (e.g. the happy faces on either side of the fearful face), but I think that this is actually quite a poor model of how distraction works in real life. I am interested in looking in more detail at distractors that are completely irrelevant to the task (e.g. your mobile phone buzzing during your homework, the lyrics of a music song whilst trying to read, or almost everything you do on Facebook). There may be many useful applications of this work to schools, parents and education more generally; for example surrounding the use of technology in our educational frameworks (a recent blog by @InnerDrive looked to do just this). Just as importantly, however, I hope that this research may contribute to humanising a developmental period which, for me – through its simultaneous triumphs and vulnerabilities, it’s propensity for both staggering achievement and wanton self-destruction – seems just about as gloriously ‘human’ a time as there can be.
If you are interested in a possible research project between your school and UCL on any of the aspects discussed in this blog, please don’t hesitate to get in touch.
- Heron, M. (2012). Deaths: Leading causes for 2008. National Vital Statistics Report, 6, 1–94
- Diamond, A. (2013). Executive functions. Annual Review of Psychology, 64, 135–168. http://doi.org/10.1146/annurev-psych-113011-143750
- Romine, C. B., & Reynolds, C. R. (2005). A Model of the Development of Frontal Lobe Functioning: Findings From a Meta-Analysis. Applied Neuropsychology, 12(4), 190–201. http://doi.org/10.1207/s15324826an1204
- Luciana, M., Conklin, H. M., Hooper, C. J., & Yarger, R. S. (2005). The Development of Nonverbal Working Memory and Executive Control Processes in Adolescents. Child Development, 76(3), 697 – 712.
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- Grose-Fifer, J., Rodrigues, A., Hoover, S., & Zottoli, T. (2013). Attentional capture by emotional faces in adolescence. Advances in Cognitive Psychology, 9(2), 81–91. http://doi.org/10.2478/v10053-008-0134-9
- Cohen-Gilbert, J. E., & Thomas, K. M. (2013). Inhibitory control during emotional distraction across adolescence and early adulthood. Child Development, 84(6), 1–22. http://doi.org/10.1111/cdev.12085
- Roper, Z. J. J., Vecera, S. P., & Vaidya, J. G. (2014). Value-Driven Attentional Capture in Adolescence. Psychological Science, 25(11), 1987–1993. http://doi.org/10.1177/0956797614545654
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