The Neuroscience of the Teenage Brain - with Sarah-Jayne Blakemore

00:56:02
https://www.youtube.com/watch?v=yQXhFa8dRCI

ุงู„ู…ู„ุฎุต

TLDRThe talk, centered on the teenage brain, delves into 16 years of research conducted at University College London (UCL). The speaker transitions from using scientific slides to a more descriptive approach, reflective of the book they authored on adolescent brain research. A notable reader example emphasizes personal significance versus historic events, showcasing how teenagers prioritize personal and social aspects over the extraordinary. The speaker also highlights societal tendencies to mock adolescents, often ignored for other age groups, and discusses adolescence as a transformative phase for identity and social development. A significant part of the dialogue revolves around defining adolescence, noting differing definitions like that of the World Health Organization and historical perspectives provided by Stanley Hall. The teenage years, marked by a quest for identity and navigating peer influence, are explored with examples showing societal perceptions across cultures and species, such as mice exhibiting similar risk-taking behaviors. The biology of the adolescent brain is meticulously discussed, revealing increases in white matter and decreases in gray matter, an indication of brain maturation. The talk also touches on behavior patterns such as risk-taking, embarrassment, and social influence, with illustrations of how these change across adolescence. The speaker challenges assumptions of adolescence as a dysfunctional stage, asserting its crucial role in developing independence and adult identity. The talk concludes with a passionate recitation from a youth theater production, reinforcing the theme that the adolescent brain is not broken but is in a unique, formative stage of development.

ุงู„ูˆุฌุจุงุช ุงู„ุฌุงู‡ุฒุฉ

  • ๐Ÿง  The teenage brain undergoes significant development, crucial for forming identity and social connections.
  • ๐Ÿ“ˆ Adolescence is defined variably, with no agreed end age, reflecting cultural differences.
  • ๐Ÿ™…โ€โ™‚๏ธ Society often mocks teenagers, a unique social acceptance not seen in other age groups.
  • ๐Ÿ“‰ Gray matter decreases while white matter increases in the adolescent brain, indicating maturation.
  • ๐ŸŒ Adolescent behaviors like risk-taking are seen across cultures and species, such as in mice.
  • ๐Ÿ‘ฅ Peer influence is a dominant factor in teenage decision-making and risk-taking behaviors.
  • ๐Ÿ”„ The concept of adolescence is not recent; historical figures have noted similar behaviors for centuries.
  • ๐ŸŒŸ The adolescent stage is formative, not flawed, essential for developing independence and adult identity.
  • ๐Ÿ“Š Studies show similar adolescent behaviors in diverse cultures, highlighting global patterns.
  • ๐ŸŽญ A youth theater group's portrayal of the teenage brain reflects societal and personal insights.

ุงู„ุฌุฏูˆู„ ุงู„ุฒู…ู†ูŠ

  • 00:00:00 - 00:05:00

    The speaker discusses their long-term research on the teenage brain at UCL, highlighting the importance of adolescence for social self-identity development. They note society's tendency to mock teenagers and emphasize adolescence as integral for becoming independent adults.

  • 00:05:00 - 00:10:00

    The speaker addresses the different perspectives on when adolescence ends, mentioning varying views and definitions by different organizations and individuals. They note that cultural differences impact the perception and duration of adolescence, defining it as the period between puberty and achieving a stable, independent societal role.

  • 00:10:00 - 00:15:00

    There are universal behavioral patterns during adolescence, including risk-taking and impulsivity, regardless of cultural differences. The speaker highlights studies showing that these behaviors are seen across different cultures and even in non-human species, indicating adolescence is a crucial developmental stage rather than a cultural invention.

  • 00:15:00 - 00:20:00

    The speaker shares historical perspectives to illustrate that adolescence has always been seen similarly throughout history, citing philosophers and playwrights. They explain their shift from schizophrenia research to studying the developing teenage brain due to the peak onset age of psychiatric symptoms and encouragement from mentors.

  • 00:20:00 - 00:25:00

    Using MRI technology, scientists have learned extensively about brain development. The speaker explains ongoing brain changes during adolescence, including increased white matter and decreased gray matter, and the significance of these changes in cognitive and behavioral development.

  • 00:25:00 - 00:30:00

    Neurodevelopment during adolescence involves processes like myelination and synaptic pruning, leading to increased brain efficiency and neuroplasticity. These changes help adapt brain functions to environmental demands and are essential to understanding adolescent behavior and decision-making processes.

  • 00:30:00 - 00:35:00

    The speaker discusses the heightened sense of embarrassment and social awareness in adolescents, explaining a study that shows adolescents are more self-conscious and physiologically reactive when they believe others are observing them, compared to children and adults.

  • 00:35:00 - 00:40:00

    Adolescents are more likely to engage in risk-taking, especially in social settings, due to peer influence. The speaker emphasizes that risk-taking is not unique to adolescents but is influenced by social contexts where peer approval is sought. Demonstrations and studies illustrate these tendencies and their real-life implications.

  • 00:40:00 - 00:45:00

    Participants demonstrate a balloon task to highlight differences in risk-taking behavior among age groups. The experiment showcases the correlation between adolescent risk-taking in controlled tasks and real-life behaviors, emphasizing social influence as a key factor in adolescent risk propensity.

  • 00:45:00 - 00:50:00

    A study shows that peer presence significantly increases risk-taking in adolescents compared to adults. The speaker notes policy implications and emphasizes adolescents' hypersensitivity to social exclusion, which can explain certain decision-making behaviors, shedding light on the rationale behind risking social ostracism over health risks.

  • 00:50:00 - 00:56:02

    The speaker concludes by advocating for a positive perception of the adolescent brain, likening it to a developmental phase rather than a defective state. They highlight the importance of supporting and celebrating adolescence, underscoring the period's role in shaping individuality and potential, capped off by a youth performance emphasizing similar themes.

ุงุนุฑุถ ุงู„ู…ุฒูŠุฏ

ุงู„ุฎุฑูŠุทุฉ ุงู„ุฐู‡ู†ูŠุฉ

Mind Map

ุงู„ุฃุณุฆู„ุฉ ุงู„ุดุงุฆุนุฉ

  • Who led the research on the teenage brain?

    The research was led by a group at UCL, overseen by the speaker.

  • How does the speaker usually give talks?

    The speaker typically uses science slides but adopted a mixed format for this book talk.

  • What was the reader Dina Hall's entry in her teenage diary about?

    Her entry detailed personal interactions and fashion choices rather than the historic moon landing.

  • What is the societal view on mocking teenagers, according to the speaker?

    Society finds it acceptable to mock teenagers, unlike other age groups.

  • What is the WHO's definition of adolescence?

    The World Health Organization defines adolescence as the second decade of life, ages 10 to 20.

  • Do adolescents experience peer influence differently than adults?

    Yes, adolescents are more influenced by peers, affecting their risk-taking behavior.

  • What usually influences adolescent risk-taking?

    Social situations, particularly peer presence, heighten risk-taking tendencies in adolescents.

  • When does the brain stop developing according to the speaker?

    The speaker suggests the brain never truly stops developing due to its neuroplasticity.

  • What distinguishes human brain development mentioned in the talk?

    White matter increases during adolescence while gray matter decreases.

  • What comparison does the speaker make with other species?

    Adolescent behaviors like risk-taking are observed in other species, such as mice and wombats.

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en
ุงู„ุชู…ุฑูŠุฑ ุงู„ุชู„ู‚ุงุฆูŠ:
  • 00:00:05
    [Music]
  • 00:00:09
    I'm gonna talk a bit about the teenage
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    brain this is a subject that I've been
  • 00:00:15
    working on for about the last 16 years
  • 00:00:17
    I've been running a group at UCL and we
  • 00:00:20
    we research the teenage brain and thank
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    you and actually it's interesting cuz I
  • 00:00:28
    have very rarely do I give talks with
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    notes I normally just have loads of
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    science slides behind me which I talk
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    about but because this is a book talk I
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    thought it would be better to kind of
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    mix up a few sides with more of a
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    description which is a sort of
  • 00:00:44
    representation of what's in my book so
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    yeah the last three years in my
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    so-called spare time I've been writing
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    about the research that we do on the
  • 00:00:53
    teenage brain and I'd like to start this
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    talk with this nice letter which was
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    written by a reader who wrote to The
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    Guardian newspaper so this is Dina Hall
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    a reader of the Guardian newspaper who
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    says there's nothing like teenage
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    Diaries for putting momentous historical
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    events in perspective this is my entry
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    for the 20th of July 1969 I went to Art
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    Center by myself in yellow cords and
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    blouse Ian was there but he didn't speak
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    to me got a poem put in my handbag from
  • 00:01:27
    someone who's apparently got a crush on
  • 00:01:28
    me it's Nicholas I think oh man landed
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    on moon
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    this is a really nice illustration
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    because it shows us what's important to
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    that particular teenage girl at that
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    particular moment in her life less
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    important is the fact that man happened
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    to land on the moon for the very first
  • 00:01:49
    time that day and more important to
  • 00:01:52
    things like what she's wearing who she
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    likes who she doesn't like who she's
  • 00:01:56
    hanging out with adolescence is the
  • 00:01:58
    period of life that where we in which we
  • 00:02:01
    develop our sense of self our sense of
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    self-identity and particularly our sense
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    of social self that is how other people
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    see us that I think is what adolescents
  • 00:02:11
    this period of life that I'm talking
  • 00:02:12
    about today is all about it's developing
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    a sense of who you are and particularly
  • 00:02:18
    how other people see you so how you're
  • 00:02:20
    seen in your local community that that
  • 00:02:24
    is what adolescence is about it's about
  • 00:02:26
    constructing ourselves so as John said
  • 00:02:30
    we as a society um
  • 00:02:33
    appear to think that it's completely
  • 00:02:35
    acceptable to mock this age group like
  • 00:02:37
    John said whenever I tweet about working
  • 00:02:40
    on the adolescent brain invariably I
  • 00:02:43
    will get a tweet back saying a tweet
  • 00:02:45
    back saying something like well that's
  • 00:02:46
    not going to take very long is it
  • 00:02:48
    implying I think that there's no brain
  • 00:02:50
    defined or it's very small I'm not quite
  • 00:02:52
    sure what that implies but I'll always
  • 00:02:54
    get some kind of reply jokey reply about
  • 00:02:57
    teenagers it's a really interesting
  • 00:02:58
    phenomenon that we as a society allow
  • 00:03:02
    ourselves to laugh at this age group in
  • 00:03:05
    a way and you know there are whole funny
  • 00:03:07
    comedy shows on exactly that subject
  • 00:03:10
    mocking teenagers and it's interesting
  • 00:03:13
    because we don't really find it socially
  • 00:03:15
    acceptable to do that with any other
  • 00:03:17
    sector of society something about our
  • 00:03:21
    view of this age group allows us or
  • 00:03:25
    makes it socially acceptable to make fun
  • 00:03:28
    of them and also to demonize them a bit
  • 00:03:29
    they get they have a very kind of bad
  • 00:03:31
    reputation we are very quick to blame
  • 00:03:34
    them and to yeah and to sort of blame
  • 00:03:37
    blame their behavior which I'm going to
  • 00:03:41
    talk about a lot today on their own
  • 00:03:43
    decisions and their you know their own
  • 00:03:45
    decision to be Moody and impulsive and
  • 00:03:48
    taking and particularly influence that
  • 00:03:51
    by their peers and lazy not getting up
  • 00:03:53
    in the mornings that kind of thing but
  • 00:03:55
    actually adolescence is a really
  • 00:03:57
    fascinating period of life and it's a
  • 00:03:59
    really important period of life in which
  • 00:04:01
    we all have to go through to become
  • 00:04:04
    independent adults adolescence is really
  • 00:04:07
    fundamental to the adult we become okay
  • 00:04:12
    so I'm now going to ask you to get out
  • 00:04:14
    your mobile phones and instead of
  • 00:04:15
    turning them off I'm gonna ask you to
  • 00:04:18
    log on to the Wi-Fi so if you get out
  • 00:04:22
    your mobile phones and then once you've
  • 00:04:24
    logged on once you've got good Wi-Fi or
  • 00:04:27
    good 3G or 4G log on to mint accom Ross
  • 00:04:31
    can you show the first mentor question
  • 00:04:33
    so now what you have to do is answer
  • 00:04:35
    this question what age do you think
  • 00:04:37
    adolescent stops so when does this
  • 00:04:40
    period of life end and you've got a
  • 00:04:43
    multiple choice of five answers there so
  • 00:04:46
    if you all just put in what you think
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    and you there's no you know that I'm not
  • 00:04:49
    gonna tell you the answer now it's just
  • 00:04:51
    interesting to see whatever whatever one
  • 00:04:53
    thinks the answer is to this brilliant
  • 00:05:00
    okay so a hundred and ninety four of you
  • 00:05:03
    have entered some answer we'll just give
  • 00:05:07
    it another few seconds okay we should
  • 00:05:15
    probably move on so can we look at the
  • 00:05:16
    results so there's quite a spread of
  • 00:05:24
    responses and most people are saying age
  • 00:05:27
    twenty-five interesting that some people
  • 00:05:29
    are saying never okay
  • 00:05:34
    well I'm going to talk about that now
  • 00:05:36
    actually so what is adolescence what the
  • 00:05:39
    definition of adolescence I'm always
  • 00:05:40
    asked this and obviously is an obvious
  • 00:05:42
    question there are they actually is
  • 00:05:44
    there's no simple answer
  • 00:05:46
    some people think of adolescence as the
  • 00:05:48
    teenagers as synonymous with the teenage
  • 00:05:50
    years say thirteen to nineteen uh the
  • 00:05:54
    World Health Organization defines
  • 00:05:55
    adolescence as the second decade of life
  • 00:05:58
    so ten to twenty um
  • 00:06:00
    Stanley Hall who was the first person to
  • 00:06:02
    coin the term adolescence to describe
  • 00:06:05
    this age group about a hundred and odd
  • 00:06:06
    years ago in the u.s. described it as
  • 00:06:09
    the period of life between puberty so
  • 00:06:11
    around age twelve to thirteen back then
  • 00:06:13
    up until about age 25 the the definition
  • 00:06:17
    of adolescence that I use and lots of my
  • 00:06:19
    colleagues use is the age between
  • 00:06:21
    puberty so it starts with the physical
  • 00:06:24
    and biological changes at puberty and
  • 00:06:26
    the end of adolescence in the way we
  • 00:06:29
    define it has a much more fuzzy and
  • 00:06:32
    vague definition which is the age at
  • 00:06:34
    which you attain a stable independent
  • 00:06:37
    role in society but that's for never
  • 00:06:40
    people so that can go on a long time and
  • 00:06:45
    the interesting the interesting thing if
  • 00:06:46
    you think about it about that definition
  • 00:06:48
    is how different adolescents this
  • 00:06:52
    concept of adolescence is between
  • 00:06:54
    cultures so in our culture it's
  • 00:06:57
    completely normal and socially
  • 00:06:59
    acceptable for young people to be not
  • 00:07:02
    independent so to live at home with
  • 00:07:04
    their parents in full-time education
  • 00:07:06
    throughout their teens of course and
  • 00:07:08
    even beyond that into their 20s or even
  • 00:07:10
    their 30s whereas in other cultures
  • 00:07:13
    around the world that's not the case at
  • 00:07:15
    all and young people children are
  • 00:07:17
    expected to become independent like earn
  • 00:07:19
    their own money and as soon as they can
  • 00:07:22
    and have babies as soon as they reach
  • 00:07:24
    sexual maturity so the concept of
  • 00:07:26
    adolescence and the way and social
  • 00:07:29
    expectations of adolescents differ
  • 00:07:31
    vastly between cultures and some people
  • 00:07:34
    have argued because of those cultural
  • 00:07:36
    differences of the whole concept of
  • 00:07:38
    adolescence that this this concept is a
  • 00:07:41
    recent in
  • 00:07:42
    vention coined yes by Stanley Hall about
  • 00:07:46
    a hundred and ten years ago in America
  • 00:07:47
    is something that's new that's invented
  • 00:07:49
    recently but actually I think there are
  • 00:07:51
    some really good reasons why that's not
  • 00:07:54
    the case and why in fact adolescence is
  • 00:07:57
    a really important period of biological
  • 00:08:01
    and psychological and social development
  • 00:08:04
    before right before I before I tell you
  • 00:08:07
    about those reasons I'm gonna ask you to
  • 00:08:09
    answer a couple more questions so can we
  • 00:08:11
    can we have the next question so get
  • 00:08:12
    your phones back out mentee it will go
  • 00:08:14
    if you just refresh the page you'll get
  • 00:08:16
    the next question so when at what age do
  • 00:08:20
    you think the human brain stops
  • 00:08:22
    developing
  • 00:08:39
    okay so can we showed the results no
  • 00:08:46
    it's interesting so most people are
  • 00:08:47
    saying never and some people are saying
  • 00:08:49
    24 and some 30 okay I'll come back to
  • 00:08:53
    that later one more question if you go
  • 00:08:55
    press refresh okay the question this is
  • 00:08:58
    a tricky question the question is how
  • 00:09:00
    many neurons does a newborn baby's brain
  • 00:09:03
    contain but I'm going to give you a clue
  • 00:09:05
    so the clue is that it's an adult human
  • 00:09:07
    brain so most people in this room an
  • 00:09:10
    adult human brain contains 80 around 86
  • 00:09:14
    billion neurons so knowing that how many
  • 00:09:18
    neurons does a newborn human babies
  • 00:09:20
    brain contain okay can we show the
  • 00:09:34
    results so most people think newborn
  • 00:09:40
    brain contains 240 billion and some
  • 00:09:44
    people 86 billion okay I will come back
  • 00:09:46
    to those later on in the talk and can
  • 00:09:49
    you go back to my slides now please Ross
  • 00:09:53
    thanks okay so I mentioned that there
  • 00:09:57
    are these big cultural differences in
  • 00:09:59
    the way we think about adolescence but
  • 00:10:01
    nevertheless it seems that certain
  • 00:10:03
    adolescent typical behaviors by which I
  • 00:10:06
    mean behaviors like behaviors that we
  • 00:10:08
    stereotypically associate with this age
  • 00:10:10
    group so behaviors like increased risk
  • 00:10:13
    taking or impulsivity peer influence
  • 00:10:17
    heightened self-consciousness behaviors
  • 00:10:21
    that we we tend to think of when you
  • 00:10:23
    when you hear the word teenager or
  • 00:10:24
    adolescent you can see those behaviors
  • 00:10:26
    across cultures even in cultures where
  • 00:10:29
    societal expectations of this age group
  • 00:10:31
    vastly differ so there was one
  • 00:10:34
    experiment there are actually very few
  • 00:10:36
    experimental research studies looking at
  • 00:10:39
    that it's really hard to do as you can
  • 00:10:41
    imagine but there was one study
  • 00:10:42
    published a couple of years ago and she
  • 00:10:44
    probably published about one year one
  • 00:10:45
    and a half years ago by Larry Steinberg
  • 00:10:48
    and his colleagues they studied
  • 00:10:50
    different behaviors across 11 different
  • 00:10:53
    cultures and these cultures are very
  • 00:10:55
    different in terms of how young people
  • 00:10:57
    are treated and the expectations placed
  • 00:11:00
    on those young people nevertheless they
  • 00:11:03
    showed pretty similar developmental
  • 00:11:05
    trajectories of two particular behaviors
  • 00:11:08
    one is sensation-seeking
  • 00:11:10
    sensation-seeking is defined as the
  • 00:11:14
    desire to seek novelty and to take risks
  • 00:11:18
    and across those 11 different cultures
  • 00:11:21
    although there were some subtle
  • 00:11:22
    differences most of those cultures
  • 00:11:25
    showed a very similar developmental
  • 00:11:27
    pattern for sensation-seeking which is
  • 00:11:29
    this so this what you can see here is
  • 00:11:31
    sensation-seeking plotted on this axis
  • 00:11:34
    here at the vertical axis plotted
  • 00:11:36
    against age from 10 to 30 so
  • 00:11:40
    sensation-seeking increases during the
  • 00:11:43
    teenage years its highest in the late
  • 00:11:45
    teens which is what that bar corresponds
  • 00:11:48
    to here and then it decreases again
  • 00:11:50
    during the 20s so across cultures there
  • 00:11:55
    seems to be a peak in sensation-seeking
  • 00:11:57
    and risk-taking in the late teens and
  • 00:12:00
    then that declines again whereas
  • 00:12:03
    self-regulation which is the ability to
  • 00:12:07
    regulate and plan your behavior and
  • 00:12:09
    inhibit risk-taking stop stop you're
  • 00:12:12
    stopping yourself taking risks has a
  • 00:12:15
    different development or pattern which
  • 00:12:17
    is really similar across these 11
  • 00:12:18
    different cultures so across those
  • 00:12:21
    cultures sensation sensation seeking
  • 00:12:23
    sorry self-regulation improves gradually
  • 00:12:27
    during the teenage years and it levels
  • 00:12:29
    off into the 20s so teenage typical
  • 00:12:34
    behavior like sensation-seeking and also
  • 00:12:36
    the ability to regulate your impulses
  • 00:12:39
    and your actions appear to be pretty
  • 00:12:42
    invariant across cultures also across
  • 00:12:45
    species so interestingly adolescence is
  • 00:12:49
    not specific to humans it's not just
  • 00:12:52
    humans who go through undergo this
  • 00:12:54
    period of life all animals go through a
  • 00:12:57
    period of life between puberty and
  • 00:12:59
    becoming fully sexually mature adults
  • 00:13:02
    in that period of their lives you can
  • 00:13:04
    measure their behavior and lots of
  • 00:13:06
    scientists do this all around the world
  • 00:13:07
    particularly with mice and rats mice and
  • 00:13:10
    rats go through about 30 days of
  • 00:13:12
    adolescence between going through
  • 00:13:15
    puberty and becoming fully sexually
  • 00:13:17
    mature adults and in those 30 days you
  • 00:13:19
    can see increases in things like
  • 00:13:21
    risk-taking
  • 00:13:22
    and exploration of their environments
  • 00:13:25
    and changes in the way they behave
  • 00:13:26
    socially in their social behavior there
  • 00:13:29
    was one study published a few years ago
  • 00:13:32
    showing that adolescent mice drink more
  • 00:13:34
    alcohol when they're with other mice but
  • 00:13:38
    that's not the case for adult mice so
  • 00:13:39
    this this this this graph shows that
  • 00:13:42
    results so here's the amount of time
  • 00:13:44
    that the mice spend drinking alcohol
  • 00:13:47
    when they're on their own here this is
  • 00:13:51
    the blue bar is the adolescent mice and
  • 00:13:53
    the red bar is the adult mice so they
  • 00:13:55
    drink around the same amount when
  • 00:13:57
    they're on their own but when they're
  • 00:13:58
    with their cage mates adolescent mice
  • 00:14:01
    drink lots more than they did when
  • 00:14:03
    they're on their own whereas a lot mice
  • 00:14:05
    drink around the same so adolescent
  • 00:14:08
    typical behavior isn't restricted to
  • 00:14:11
    humans but you can also see it in other
  • 00:14:13
    species as well there's a nice quote I
  • 00:14:16
    dig out quote I look for and keep quotes
  • 00:14:19
    about adolescents from various
  • 00:14:20
    newspapers again this is from the
  • 00:14:22
    Guardian I don't know if you remember
  • 00:14:23
    you probably don't but about three years
  • 00:14:26
    ago two or three years ago a woman in
  • 00:14:28
    Australia was attacked by an adolescent
  • 00:14:30
    wombat it didn't really make front-page
  • 00:14:32
    news but it did make neat the newspapers
  • 00:14:35
    or at least the Guardian and the
  • 00:14:36
    Guardian had a quote from a guy called
  • 00:14:38
    Martin Lynde who was from the Australian
  • 00:14:41
    Wildlife Service and I'm not going to do
  • 00:14:43
    this in an Australian accent but you can
  • 00:14:44
    imagine it in an Australian accent he's
  • 00:14:47
    talking about adolescent wombats
  • 00:14:49
    he says as babies they're clingy they're
  • 00:14:53
    adorable they're with mum 24 hours a day
  • 00:14:56
    they're in a soft snuggly sleeping bag
  • 00:14:59
    all the time listening to a heartbeat
  • 00:15:00
    when they start to mature and hit
  • 00:15:03
    puberty they just hate everybody and
  • 00:15:05
    everything they go from running between
  • 00:15:07
    your legs and cute as a button to being
  • 00:15:09
    absolute little can I swear little shits
  • 00:15:12
    they nip you
  • 00:15:14
    Rek they bite I won't look after
  • 00:15:16
    adolescent wombats because you kiss
  • 00:15:18
    goodbye to your flooring and everything
  • 00:15:20
    they just destroy everything I saw
  • 00:15:22
    that's really nice because it could
  • 00:15:23
    equally be written about adolescent
  • 00:15:26
    humans okay
  • 00:15:29
    history the third reason why I think we
  • 00:15:32
    shouldn't think of adolescents as some
  • 00:15:34
    kind of recent Western and phenomenon is
  • 00:15:37
    because if you read descriptions of this
  • 00:15:40
    age group throughout history there are
  • 00:15:41
    many you see striking similarities with
  • 00:15:45
    the way we describe this age group today
  • 00:15:47
    so in this kind of stereotypical
  • 00:15:48
    slightly mocking slightly denigrating
  • 00:15:51
    way I'm gonna read you a few quotes so
  • 00:15:54
    this is Socrates almost two and a half
  • 00:15:56
    thousand years ago talking about youth
  • 00:15:57
    he says the children now love luxury
  • 00:16:01
    they have bad manners contempt for
  • 00:16:03
    authority they show disrespect for
  • 00:16:06
    elders and love chatter in the place of
  • 00:16:08
    exercise they all these people really
  • 00:16:11
    quite irritated with adolescents some
  • 00:16:13
    reason this is Aristotle who says the
  • 00:16:17
    young are in character prone to desire
  • 00:16:19
    and ready to carry out any meaningful
  • 00:16:21
    desire they may have formed into action
  • 00:16:23
    their changeful to and fickle in their
  • 00:16:26
    desires which are as transitory as they
  • 00:16:28
    are vehement for their wishes are keen
  • 00:16:30
    without being permanent they are
  • 00:16:32
    passionate irascible and apt to be
  • 00:16:35
    carried away by their impulses youth is
  • 00:16:38
    the age when most people are devoted to
  • 00:16:40
    their friends or when people are most
  • 00:16:42
    devoted to their friends or relations or
  • 00:16:44
    companions as they are then extremely
  • 00:16:46
    fond of social intercourse and have not
  • 00:16:49
    yet learnt to judge their friends or
  • 00:16:51
    indeed anything else by the rule of
  • 00:16:53
    expediency if the young commits a fault
  • 00:16:56
    it's always on the side of excess and
  • 00:16:58
    exaggeration for they carry everything
  • 00:17:00
    too far whether it be their love or
  • 00:17:03
    hatred or anything else I mean there's a
  • 00:17:05
    two and a half thousand years ago by
  • 00:17:07
    Aristotle very similar stereotypes to
  • 00:17:10
    the way we we sort of stereotype this
  • 00:17:12
    age group today Shakespeare that 400
  • 00:17:14
    years ago in The Winter's Tale says I
  • 00:17:16
    would there were no age between ten and
  • 00:17:19
    three and twenty or that youth would
  • 00:17:22
    sleep out the rest for there is nothing
  • 00:17:24
    in the between but getting wenches with
  • 00:17:26
    child wronging the ancient tree
  • 00:17:28
    stealing fighting reso in about a
  • 00:17:33
    century laughter Shakespeare says a
  • 00:17:36
    change in he's describing adolescence he
  • 00:17:38
    says a change in humor frequent anger a
  • 00:17:40
    mind and constant agitation makes the
  • 00:17:43
    child almost unmanageable his
  • 00:17:45
    feverishness turns him into a lion he
  • 00:17:48
    disregards his guide he no longer wishes
  • 00:17:50
    to be governed so for millennia then
  • 00:17:52
    adolescence has been paid it painted in
  • 00:17:55
    the same stereotypical terms as we often
  • 00:17:57
    use them today this certainly suggests
  • 00:17:59
    that adolescence is not some kind of
  • 00:18:01
    recent Western phenomenon so when did I
  • 00:18:06
    become interested in adolescence John
  • 00:18:08
    mentioned my PhD I did my PhD here in
  • 00:18:11
    London a long time ago on schizophrenia
  • 00:18:14
    which as you may know is a really
  • 00:18:16
    devastating psychiatric condition that's
  • 00:18:19
    characterized by symptoms like hearing
  • 00:18:22
    voices auditory hallucinations hearing
  • 00:18:24
    voices inside your head and delusions of
  • 00:18:28
    persecution or paranoia so thinking that
  • 00:18:30
    other people are out to get you and
  • 00:18:31
    you're being followed by mi5 or other
  • 00:18:35
    people trying to harm you in some way
  • 00:18:37
    I also did postdoctoral research on
  • 00:18:40
    schizophrenia in France and what I
  • 00:18:42
    noticed after testing or during testing
  • 00:18:45
    many hundreds of patients in hospitals
  • 00:18:48
    both in the UK and also in France is
  • 00:18:51
    that every time I asked a patient what
  • 00:18:54
    age did you start experiencing these
  • 00:18:56
    symptoms without a single exception they
  • 00:18:59
    all said at some age between 18 and
  • 00:19:02
    around 26 so I became interested in why
  • 00:19:05
    this was what is it about teenage brain
  • 00:19:09
    development that is different in
  • 00:19:12
    teenagers who go on to develop
  • 00:19:14
    schizophrenia at that time that was
  • 00:19:16
    around year 2001 very little was known
  • 00:19:20
    about how the human brain develops
  • 00:19:22
    virtually nothing was known about how
  • 00:19:25
    the human teenage brain develops so it
  • 00:19:28
    was around then that I decided to change
  • 00:19:30
    the focus of my own research and to
  • 00:19:32
    start studying the adolescent brain and
  • 00:19:34
    I have to say an acknowledge at this
  • 00:19:37
    point the support of one of my mentors
  • 00:19:39
    Professor hooter fris who
  • 00:19:41
    um she had been a mentor to me for many
  • 00:19:44
    years
  • 00:19:45
    I had been supervised by Christmas who
  • 00:19:48
    is her husband and they I couldn't make
  • 00:19:50
    it unfortunately but some of you may
  • 00:19:51
    have been seen there joined talked here
  • 00:19:54
    about six months ago so I was supervised
  • 00:19:57
    by Chris but it was very much one of my
  • 00:19:59
    mentors and she encouraged me to take
  • 00:20:02
    this risk because it really was a risk
  • 00:20:04
    switching fields from working with
  • 00:20:06
    patients with psychosis to working on
  • 00:20:10
    the developing brain because I had never
  • 00:20:12
    before done a developmental study but
  • 00:20:15
    without his encouragement I changed the
  • 00:20:17
    focus of my own research and and have
  • 00:20:20
    been doing that ever since
  • 00:20:23
    okay so um I asked you when you think
  • 00:20:27
    the brain stops developing and how many
  • 00:20:30
    neurons you think there are in a newborn
  • 00:20:32
    baby brain and I did that for a reason
  • 00:20:34
    because when I when I started to become
  • 00:20:39
    interested in this area and like I said
  • 00:20:41
    and and up until that point I had always
  • 00:20:44
    been taught that the human brain mostly
  • 00:20:47
    develops in very early childhood and
  • 00:20:50
    stops developing at some point in mid
  • 00:20:52
    childhood that's what I had learned
  • 00:20:54
    during my undergraduate degree I know
  • 00:20:57
    that because I kept my undergraduate
  • 00:20:59
    textbooks and I still have them and they
  • 00:21:01
    say things like that they talk about how
  • 00:21:03
    human brain development stops in
  • 00:21:05
    childhood and that's because that's
  • 00:21:07
    completely wrong and that that's a dogma
  • 00:21:12
    that false dogma that we were taught was
  • 00:21:15
    simply because actually no one really
  • 00:21:16
    knew and they were making an informed
  • 00:21:18
    guess based on mostly based on animal
  • 00:21:21
    research and on research with
  • 00:21:23
    post-mortem human brains but since
  • 00:21:25
    around the mid 90s scientists all around
  • 00:21:29
    the world have been able to scan the
  • 00:21:32
    living human brain of all ages using MRI
  • 00:21:36
    scanning so some of you may have had an
  • 00:21:37
    MRI scan either for clinical reasons or
  • 00:21:41
    for research that's what it looks like
  • 00:21:43
    you lie inside the tube of an MRI
  • 00:21:45
    scanner and that kind of scanner can be
  • 00:21:48
    used to scan your body or your brain in
  • 00:21:50
    research in neuroscience we're really
  • 00:21:52
    interested in
  • 00:21:53
    using MRI to for example tell us about
  • 00:21:57
    the structure of the human brain that's
  • 00:21:59
    what you can see here and we measure
  • 00:22:01
    using these structural MRI images we
  • 00:22:04
    measure things like the volume of gray
  • 00:22:05
    matter and the volume of white matter so
  • 00:22:08
    if I just take my brain here mostly gray
  • 00:22:11
    matter is found in the surface of the
  • 00:22:12
    brain in the cortex which is just
  • 00:22:14
    underneath the skull and gray matter
  • 00:22:17
    contains neuronal cell bodies and
  • 00:22:20
    connections between cells finances
  • 00:22:23
    amongst other things and we also measure
  • 00:22:26
    white matter which is mostly found in
  • 00:22:28
    the center of the brain and white matter
  • 00:22:31
    white matter contains the long fibers
  • 00:22:36
    along which electrical impulses pass
  • 00:22:39
    from neuron to neuron and they those act
  • 00:22:42
    they're called axons those axons allow
  • 00:22:44
    neurons and brain regions to communicate
  • 00:22:47
    with each other so we are able with MRI
  • 00:22:49
    to measure the amount of gray matter and
  • 00:22:52
    white matter the human brain contains
  • 00:22:54
    and look at how that changes across the
  • 00:22:56
    lifespan we also use MRI to scan the
  • 00:23:00
    brain while it's active so while you're
  • 00:23:02
    doing a particular task and we cook a
  • 00:23:04
    brain activity and how that changes
  • 00:23:06
    across the lifespan so one of those MRI
  • 00:23:09
    studies taught us about the developing
  • 00:23:11
    brain the answer is a huge amount so we
  • 00:23:15
    if we if we focus on the structural
  • 00:23:17
    studies and the amount of gray matter
  • 00:23:20
    and white matter of the brain contains
  • 00:23:22
    so first of all white matter we know
  • 00:23:24
    from many many studies but including one
  • 00:23:27
    that's been done recently by many people
  • 00:23:30
    including Kate Mills Kate was a PhD
  • 00:23:33
    student here with me at UCL she's now
  • 00:23:36
    she's now a an assistant professor at
  • 00:23:39
    Oregon at the University of Oregon and
  • 00:23:41
    Christiane Tammuz who is at the
  • 00:23:43
    University of Oslo amongst many other
  • 00:23:46
    people looked at MRI scans from many
  • 00:23:50
    different people many different children
  • 00:23:52
    and adolescents in four different places
  • 00:23:54
    so at NIH in Pittsburgh which are both
  • 00:23:57
    in the USA in Leiden in the Netherlands
  • 00:24:00
    and Oslo in Norway so in total not 391
  • 00:24:06
    parties
  • 00:24:07
    since children adolescents young adults
  • 00:24:09
    were scanned and each one was scanned
  • 00:24:12
    every couple of years as they got older
  • 00:24:14
    so this is a longitudinal study of of
  • 00:24:18
    brain development and altogether we were
  • 00:24:21
    analyzing 852 MRI scans from different
  • 00:24:24
    people so what you can see first of all
  • 00:24:26
    is that the amount of white matter in
  • 00:24:29
    the brain increases across childhood and
  • 00:24:32
    adolescence so this this is the amount
  • 00:24:35
    of white matter in the brain plotted
  • 00:24:37
    against age from 5 to 30 and that in all
  • 00:24:41
    of the four different cohorts so that
  • 00:24:44
    that's what these words correspond to
  • 00:24:46
    here the four different cohorts so NIH
  • 00:24:49
    and Pittsburgh and light Leiden and
  • 00:24:52
    ozlowe all of them showed a significant
  • 00:24:56
    linear increase in white matter white
  • 00:24:59
    matter increases about one percent per
  • 00:25:02
    year
  • 00:25:03
    throughout the whole of adolescence so
  • 00:25:05
    the brain is increasing the amount of
  • 00:25:08
    white matter it contains but
  • 00:25:10
    interestingly it's not getting bigger
  • 00:25:13
    the brain does not get bigger from about
  • 00:25:15
    age eight or nine from about age eight
  • 00:25:17
    or nine the human brain is pretty much
  • 00:25:20
    adult size so the brain doesn't grow but
  • 00:25:23
    the amount of white matter
  • 00:25:24
    it contains increases and at the same
  • 00:25:27
    time the amount of gray matter decreases
  • 00:25:30
    perhaps not surprisingly the whole brain
  • 00:25:32
    isn't growing so something has to
  • 00:25:33
    decrease and that's gray matter and
  • 00:25:35
    that's what you can see here so this is
  • 00:25:37
    gray matter across the cortex so the
  • 00:25:39
    surface of the brain the whole of the
  • 00:25:41
    surface of the brain averaged again in
  • 00:25:44
    the four different cohorts showing a
  • 00:25:46
    very similar pattern of a gray matter
  • 00:25:50
    being highest in late childhood and then
  • 00:25:53
    decreasing during adolescence and
  • 00:25:55
    plateauing off into the 20s
  • 00:25:56
    um the brain loses about 1.5 percent of
  • 00:26:00
    its gray matter
  • 00:26:01
    each year during the period of
  • 00:26:04
    adolescence so it's a really substantial
  • 00:26:05
    decrease in gray matter now that might
  • 00:26:08
    sound bad it might sound like neuro
  • 00:26:11
    degeneration or decline but actually we
  • 00:26:13
    don't think it we don't think this
  • 00:26:15
    decline in gray matter represents any
  • 00:26:17
    kind of degeneration and
  • 00:26:19
    we partly because it then plateaus off
  • 00:26:22
    and stabilizes for many many decades and
  • 00:26:24
    doesn't change after that but also
  • 00:26:26
    because of what we think is going on at
  • 00:26:29
    a cellular level to underlie this
  • 00:26:32
    decrease in gray matter so that's what
  • 00:26:34
    I'm going to talk about now
  • 00:26:35
    why does gray matter decrease and white
  • 00:26:37
    matter increase during adolescence well
  • 00:26:40
    the first thing to say is that we don't
  • 00:26:42
    actually know because MRI scans although
  • 00:26:44
    they give us these beautiful pictures of
  • 00:26:45
    the human brain they don't show us the
  • 00:26:48
    brain at the level of the of the cells
  • 00:26:50
    or the sign APS's for that we have to go
  • 00:26:54
    to animal studies and to studies of
  • 00:26:56
    post-mortem human brain tissue which we
  • 00:26:59
    can look at on slices of under a
  • 00:27:01
    microscope and from those studies we
  • 00:27:04
    know that during adolescence three
  • 00:27:06
    really important neurodevelopmental
  • 00:27:08
    processes are happening
  • 00:27:10
    the first is myelination which is where
  • 00:27:13
    the axons those fibers along which
  • 00:27:15
    electrical impulses travel become coated
  • 00:27:18
    in a substance called myelin it's a
  • 00:27:21
    fatty substance and it appears white
  • 00:27:23
    under the microscope and that is what
  • 00:27:25
    white matter corresponds to when we when
  • 00:27:28
    we see it in MRI scans so myelination
  • 00:27:31
    the axons are being coated in myelin
  • 00:27:33
    which by the way enables the the signal
  • 00:27:38
    transmission to be speedier it speeds up
  • 00:27:41
    signal transmission along the axon and
  • 00:27:43
    we know that that's happening during the
  • 00:27:45
    period of adolescence which is probably
  • 00:27:47
    why you see this increase in white
  • 00:27:48
    matter in the brain also axons are
  • 00:27:52
    growing so those fibers are growing in
  • 00:27:53
    diameter and that will also speed up the
  • 00:27:56
    signal of the transmission speed of the
  • 00:28:00
    signals along the axon and it will also
  • 00:28:02
    result in an increase in white matter
  • 00:28:04
    during adolescence as seen in MRI and at
  • 00:28:08
    the same time and by the way if the
  • 00:28:11
    brain is not growing then as it becomes
  • 00:28:13
    more white it has to have a concomitant
  • 00:28:15
    decrease in gray matter
  • 00:28:17
    so that will account partly for the
  • 00:28:19
    decrease in gray matter we see but both
  • 00:28:21
    of those processes are really important
  • 00:28:24
    neurodevelopmental mechanisms and
  • 00:28:26
    another third neurodevelopmental
  • 00:28:28
    mechanism that's happening in
  • 00:28:30
    adolescence is synaptic pruning whereby
  • 00:28:33
    finances that are being used in a
  • 00:28:35
    particular environment remain and are
  • 00:28:38
    strengthened and sign apses that are not
  • 00:28:41
    being used in that particular
  • 00:28:42
    environment are the ones that get pruned
  • 00:28:45
    away and eliminated and in that way the
  • 00:28:49
    environment plays a role in shaping the
  • 00:28:51
    development of the brain during the
  • 00:28:54
    period of adolescence and these all
  • 00:28:56
    these three processes can lead to
  • 00:28:57
    increased neuroplasticity during
  • 00:29:00
    adolescence so hightly the way the brain
  • 00:29:02
    adapts to its environment and changes
  • 00:29:05
    according to environmental stimuli um
  • 00:29:08
    okay so just to go back to those
  • 00:29:10
    questions that I asked you about the
  • 00:29:12
    brain so when does the human brain stop
  • 00:29:14
    developing well in some ways it's a
  • 00:29:16
    trick question it's question I'm asked
  • 00:29:17
    all the time by the way in the context
  • 00:29:19
    of things like ages of consent age of
  • 00:29:21
    criminal responsibility yeah legal
  • 00:29:24
    implications when children when young
  • 00:29:26
    people should be able to vote that kind
  • 00:29:28
    of thing and actually it's not really a
  • 00:29:31
    question that makes much sense because
  • 00:29:33
    firstly we don't really know what her
  • 00:29:36
    adult brain looks like I mean maybe we
  • 00:29:38
    won't one day but at the moment we don't
  • 00:29:40
    have a kind of clear idea of what a scan
  • 00:29:42
    of an adult brain versus a child brain
  • 00:29:44
    would do it like certainly not in a
  • 00:29:45
    single scan single subject level also
  • 00:29:49
    there's a sort of age range different
  • 00:29:51
    different brain regions develop at
  • 00:29:54
    different rates
  • 00:29:55
    there are huge individual differences so
  • 00:29:58
    different people's brains develop at
  • 00:30:00
    different rates and finally in some ways
  • 00:30:04
    and I think lots of you answered it
  • 00:30:06
    never stops developing I think that's
  • 00:30:07
    right the brain never really stops
  • 00:30:09
    changing at least this these kinds of I
  • 00:30:11
    mentioned neuroplasticity there's no age
  • 00:30:14
    limit to neuroplasticity whenever you
  • 00:30:16
    learn anything new something probably a
  • 00:30:18
    few cells and sign APS's and your brain
  • 00:30:20
    have changed they've grown stronger and
  • 00:30:22
    there's no age limit to that you can
  • 00:30:25
    learn new things at any age because of
  • 00:30:27
    neuroplasticity and the the third
  • 00:30:30
    question I asked you about how many
  • 00:30:32
    neurons does a beta noob or baby brain
  • 00:30:34
    contain okay so the answer was exactly
  • 00:30:38
    the same as an adult brain eighty six
  • 00:30:40
    billion and I it's a kind of trick
  • 00:30:42
    question and it's a bit mean because a
  • 00:30:44
    lot of you answered I
  • 00:30:46
    240 billion or whatever that the the
  • 00:30:48
    figure that was higher than the number
  • 00:30:51
    of neurons in the adult brain but
  • 00:30:53
    actually the number of neurons the
  • 00:30:55
    number of cells which is what you can
  • 00:30:57
    see here the diagram of in the brain
  • 00:30:59
    doesn't change very much at all there's
  • 00:31:02
    some neurogenesis there's some
  • 00:31:04
    generation of new neurons not very much
  • 00:31:06
    and there's some neuronal death again
  • 00:31:08
    not much the the change that the the
  • 00:31:12
    number of neurons remains pretty stable
  • 00:31:14
    throughout life from birth all the way
  • 00:31:16
    into old age what changes is the number
  • 00:31:19
    of sign APS's and that and you are right
  • 00:31:22
    that the number of sign APS's is hugely
  • 00:31:26
    greater in childhood the brain massively
  • 00:31:29
    over produces silences in childhood and
  • 00:31:33
    then it has to get rid of those sign
  • 00:31:35
    answers and that is where synaptic
  • 00:31:36
    pruning comes in so when I was a
  • 00:31:43
    teenager most teenage typical behaviors
  • 00:31:46
    which I've talked about a lot were put
  • 00:31:48
    down to changing hormones and changing
  • 00:31:52
    and sort of social changes like changing
  • 00:31:53
    schools but actually now we know that
  • 00:31:57
    the brain changes hugely as well these
  • 00:32:00
    changes in the brain are at least part
  • 00:32:03
    of the jigsaw puzzle in trying to
  • 00:32:04
    understand adolescent the transition of
  • 00:32:08
    adolescent and adolescent typical
  • 00:32:10
    behavior so what are some of these
  • 00:32:13
    behaviors well one is embarrassment
  • 00:32:14
    embarrassment is something that really
  • 00:32:16
    seems to kick in in adolescents
  • 00:32:19
    particularly embarrassment in front of
  • 00:32:20
    your parents one of my friends said to
  • 00:32:22
    me that the the main difference that he
  • 00:32:25
    noticed in his children before his two
  • 00:32:27
    daughters before and after puberty was
  • 00:32:30
    in their levels of embarrassment
  • 00:32:32
    particularly in front of him so before
  • 00:32:33
    puberty if they were messing around in
  • 00:32:35
    us in a shop say he would say stop
  • 00:32:37
    messing around on I'll sing your
  • 00:32:38
    favorite song and they would instantly
  • 00:32:40
    be quiet and to sing to them and after
  • 00:32:42
    puberty that became the threat
  • 00:32:45
    the idea of their dad singing in public
  • 00:32:48
    was enough to make them behave there are
  • 00:32:51
    so many examples of adolescent
  • 00:32:53
    embarrassment I have a friend who
  • 00:32:55
    recently bought a pair of blue trainers
  • 00:32:58
    and his 14 year old son immediately said
  • 00:33:00
    did you choose them off the
  • 00:33:02
    midlifecrisis shelf and he's banned from
  • 00:33:06
    wearing those trainers in the entire
  • 00:33:08
    village in which his two teenage sons go
  • 00:33:10
    to school and they make him keep a pet a
  • 00:33:12
    spare pair of shoes in the car just in
  • 00:33:14
    case he forgets that rule even my own
  • 00:33:16
    children so I'm a governor at my
  • 00:33:18
    children's school the primary and the
  • 00:33:20
    secondary school both of them and the
  • 00:33:22
    difference between my 10 year old and my
  • 00:33:24
    13 year olds reaction to this is just
  • 00:33:26
    startling so my tenure we had a recent
  • 00:33:28
    visit for governor's to the schools my
  • 00:33:30
    10 year old was like can I organize your
  • 00:33:32
    visit can I show you around I'm gonna
  • 00:33:33
    ask my teacher for I can show you around
  • 00:33:34
    my 13 year old said looking really
  • 00:33:37
    horrified oh my god do you mind if I
  • 00:33:39
    pretend not to know who you are so why
  • 00:33:43
    is this well there's a there was a study
  • 00:33:45
    carried out by Leia Somerville at
  • 00:33:48
    Harvard a few years ago where she put
  • 00:33:50
    people in an MRI scanner and she
  • 00:33:53
    recorded brain activity well she told
  • 00:33:55
    them that they were being observed so
  • 00:33:58
    she said occasionally when you're lying
  • 00:34:00
    in this tiny tube a red light will come
  • 00:34:02
    on in front of you and that indicates
  • 00:34:03
    that you're being observed by two people
  • 00:34:05
    your own age in the in the scanning
  • 00:34:08
    control room in fact this is just a
  • 00:34:09
    cover story and they weren't being
  • 00:34:11
    observed but what she found was that
  • 00:34:13
    during the when the red light came on
  • 00:34:15
    when when people thought they were being
  • 00:34:17
    observed that led to increases in the
  • 00:34:21
    self rated level of embarrassment in the
  • 00:34:24
    adolescents compared with children and
  • 00:34:26
    adults also the amount of sweat the skin
  • 00:34:29
    produces which is a which is a measure
  • 00:34:31
    of stress was highest in the adolescents
  • 00:34:34
    higher than in children or adults and
  • 00:34:36
    part of the social brain called the
  • 00:34:39
    medial prefrontal cortex which is right
  • 00:34:41
    at the front in the middle of the brain
  • 00:34:43
    its activity was higher in adolescence
  • 00:34:46
    than in adults so there seems to be
  • 00:34:49
    something kind of physiological
  • 00:34:51
    underlying this increased
  • 00:34:53
    self-consciousness we feel as
  • 00:34:55
    adolescents
  • 00:34:58
    okay I'm going to talk about risk-taking
  • 00:35:00
    which is another adolescent typical
  • 00:35:02
    behavior we worry about teenagers taking
  • 00:35:06
    risks and actually I mean there are so
  • 00:35:10
    many examples of this but one one
  • 00:35:11
    example that I experienced recently a
  • 00:35:14
    couple of summers ago I was driving home
  • 00:35:17
    and I I was on an a road very fast very
  • 00:35:23
    dark a road in the middle of the night
  • 00:35:25
    driving home from Oxford to my house in
  • 00:35:28
    Hartford sure and I noticed a girl
  • 00:35:31
    walking along this road I mean
  • 00:35:32
    pitch-black road cars going 60 miles an
  • 00:35:35
    hour occasional occasional cars so I
  • 00:35:36
    stopped and said well you know do you
  • 00:35:39
    want a lift home where you going she got
  • 00:35:40
    in the crash yes that would be nice and
  • 00:35:42
    turned out she'd been in a pub she was
  • 00:35:44
    at 18 she'd been in a pub she's having a
  • 00:35:46
    great time with her friends she spent
  • 00:35:48
    her taxi money on beer she had let her
  • 00:35:51
    phone ran out of battery she was filming
  • 00:35:53
    her friends put on Facebook or whatever
  • 00:35:55
    probably not Facebook actually that's
  • 00:35:56
    really uncool with young people
  • 00:35:59
    she obviously the buses had stopped I
  • 00:36:02
    mean so she was gonna walk home I said
  • 00:36:04
    alright how far is your home eight miles
  • 00:36:06
    away so she was planning to walk eight
  • 00:36:08
    miles in the middle of the night and I
  • 00:36:09
    feel that you know that's the kind of
  • 00:36:11
    thing I probably would have done when I
  • 00:36:13
    was 18 but I wouldn't dream of doing it
  • 00:36:14
    now there is something about adolescence
  • 00:36:17
    which does make us as adolescent when
  • 00:36:19
    we're adolescents more susceptible to
  • 00:36:22
    taking risks but what I think is really
  • 00:36:26
    important is the the idea that it's not
  • 00:36:28
    just as simple as that
  • 00:36:30
    not all adolescents take risks lots of
  • 00:36:32
    adults take risks lots of risks are
  • 00:36:34
    really beneficial we learn by trial and
  • 00:36:36
    error and risks can benefit us and also
  • 00:36:39
    the the context of risk-taking this
  • 00:36:43
    particularly the social context like the
  • 00:36:45
    girl I picked up the young woman I
  • 00:36:47
    picked up it's all about being out with
  • 00:36:49
    her friends that's why she was willing
  • 00:36:51
    to take the risk of of not abandoning
  • 00:36:56
    all her safe ways of getting home
  • 00:36:58
    because she was having fun with her
  • 00:36:59
    friends so in the kind of heat of the
  • 00:37:01
    moment particularly when with friends I
  • 00:37:02
    think that's when adolescents are most
  • 00:37:04
    likely to take risks
  • 00:37:05
    okay I've now got a demonstration
  • 00:37:10
    experiment risk-taking experiments so
  • 00:37:12
    this is a balloon it's called it's
  • 00:37:14
    called um it's called the Bart task
  • 00:37:16
    which is the balloon analog risk-taking
  • 00:37:18
    task it's a very weird task but it's
  • 00:37:21
    very interesting then I'll tell you
  • 00:37:22
    about it afterwards so I need some
  • 00:37:24
    volunteers I need eight volunteers
  • 00:37:26
    preferably of different ages but it
  • 00:37:29
    doesn't really matter if not any okay
  • 00:37:38
    you come down you come here it's quite
  • 00:37:39
    hard for me to say yeah sure and you are
  • 00:37:43
    we yeah you - yeah great when yeah we
  • 00:37:44
    need a mixture of genders you okay we've
  • 00:37:54
    got one two three four five six two more
  • 00:37:58
    yeah you one more you okay so what I
  • 00:38:03
    want you to do now there's a there's a
  • 00:38:05
    prize in this what I want you to do is
  • 00:38:09
    blow up these balloons as much as you
  • 00:38:12
    can as big as you can and the two people
  • 00:38:16
    whose balloons have the biggest
  • 00:38:18
    circumference the conference will win a
  • 00:38:20
    signed copy of my book I don't know
  • 00:38:24
    whether that's really a prize or not but
  • 00:38:25
    anyway I've got them here and if I ever
  • 00:38:29
    eat Jack and Jerry - if you can come
  • 00:38:30
    down cuz they're gonna they're gonna
  • 00:38:31
    measure with these very scientific
  • 00:38:33
    instruments they're not scientific tool
  • 00:38:36
    and they're also different which is
  • 00:38:37
    probably a problem but anyway this
  • 00:38:39
    circumference of these balloons and
  • 00:38:43
    they're also gonna take our name so and
  • 00:38:46
    be careful cuz the balloons can pop so
  • 00:38:51
    you want to you want to blow up the
  • 00:38:52
    balloon and when you think you've got it
  • 00:38:53
    as big as you can without it popping try
  • 00:38:56
    and tie a knot in it and give it to one
  • 00:38:59
    of my assistants Jack Andrews is doing a
  • 00:39:03
    PhD with me and Javita lung is about to
  • 00:39:06
    do a PhD do
  • 00:39:16
    okay so I think your your um so yeah if
  • 00:39:24
    you if you measure the balloons yeah I
  • 00:39:34
    can you you can do some estimation this
  • 00:39:39
    is not a real experiment there's a
  • 00:39:42
    digital version of this task that you
  • 00:39:45
    can do on a computer and interestingly
  • 00:39:46
    okay so that the finding is that
  • 00:39:50
    adolescents take more risks on this on
  • 00:39:52
    this kind of task where they're
  • 00:39:54
    incentivized like they're gonna win a
  • 00:39:55
    reward I was just about to say um they
  • 00:40:03
    take an owner or they take more risks in
  • 00:40:05
    other words that balloons blow up more
  • 00:40:07
    than adults please do because they what
  • 00:40:09
    they want to win and they want to take
  • 00:40:10
    the risk of and it is interestingly
  • 00:40:12
    because it's such a weird task if you do
  • 00:40:20
    it on line it's obviously much more
  • 00:40:22
    controlled than this but it's a way to
  • 00:40:23
    ask but it's the the level of
  • 00:40:26
    risk-taking that you show on this task
  • 00:40:28
    is correlated with real-life risk-taking
  • 00:40:30
    like experimenting with drugs or
  • 00:40:32
    cigarettes or alcohol which is really
  • 00:40:34
    interesting
  • 00:40:38
    this is not a scientific version of the
  • 00:40:41
    star so we don't have to read anything
  • 00:40:42
    into this with these results so who won
  • 00:41:02
    [Applause]
  • 00:41:11
    so I mentioned that the the key fact the
  • 00:41:16
    key factor in in risk-taking in
  • 00:41:19
    adolescence seems to be social influence
  • 00:41:21
    there's something about being with
  • 00:41:24
    friends that make adolescents more
  • 00:41:26
    susceptible to taking risks and that was
  • 00:41:29
    shown really nicely in an experiment
  • 00:41:30
    that was carried out by Larry Steinberg
  • 00:41:33
    and their colleagues a few years ago
  • 00:41:34
    where they they had they asked
  • 00:41:36
    participants to carry out this driving
  • 00:41:38
    video game where you drive around a
  • 00:41:39
    circuit as quickly as possible and he
  • 00:41:42
    measures the number of risks you take
  • 00:41:43
    and he he studied various different age
  • 00:41:46
    groups and what you can see here is the
  • 00:41:47
    number of risks taken by adolescents
  • 00:41:51
    these are aged 13 to 16 here in this
  • 00:41:53
    leftmost
  • 00:41:55
    graph bar young adults aged 17 to 24 and
  • 00:42:00
    adults aged 25 and over and what you can
  • 00:42:03
    see is actually when they're on their
  • 00:42:04
    own when they can focus on the task at
  • 00:42:06
    hand
  • 00:42:07
    there's very little difference in the
  • 00:42:08
    number of risks adolescents and adults
  • 00:42:10
    take so this stereotype that adolescents
  • 00:42:13
    always take risks is not is just the
  • 00:42:15
    stereotype it's not always true however
  • 00:42:17
    in a second condition the research has
  • 00:42:20
    asked the participants to bring a couple
  • 00:42:22
    of friends with them and those friends
  • 00:42:24
    just stood behind the participants as
  • 00:42:26
    they carried out exactly the same
  • 00:42:27
    driving task and that resulted in three
  • 00:42:30
    times the number of risks taken by the
  • 00:42:33
    13 to 16 year olds and twice the number
  • 00:42:36
    of risks taken by the 17 to 24 year olds
  • 00:42:38
    and it had no effect on risk-taking in
  • 00:42:40
    adults so what this shows is that peer
  • 00:42:43
    influence is the really critical factor
  • 00:42:45
    in risk-taking and these kinds of data
  • 00:42:48
    are very much borne out by by real-life
  • 00:42:53
    data from car insurance companies so car
  • 00:42:55
    insurance companies as you may know when
  • 00:42:58
    you make a claim after an accident you
  • 00:43:00
    have to fill in a lot of information
  • 00:43:03
    about the precise circumstances in which
  • 00:43:05
    the accident took place and that data is
  • 00:43:07
    quantified and analyzed and what what it
  • 00:43:10
    shows is that young people under the age
  • 00:43:12
    of 26 have more accidents than older
  • 00:43:15
    people that's why their premiums are
  • 00:43:16
    higher but also it shows that the
  • 00:43:19
    precise circumstances in which
  • 00:43:22
    young people are most likely to have
  • 00:43:23
    risk have accidents is when they have
  • 00:43:27
    similar aged passengers in the car with
  • 00:43:29
    them and that's not the case for adults
  • 00:43:31
    for whom having a passenger in the car
  • 00:43:34
    is protective you're less likely to have
  • 00:43:36
    an accident if you have a passenger if
  • 00:43:37
    you're over the age of 26 and there are
  • 00:43:40
    now policy implications there are
  • 00:43:42
    countries that have brought in
  • 00:43:44
    legislation which doesn't allow young
  • 00:43:47
    people to carry non-family related
  • 00:43:51
    passengers in the car with them for a
  • 00:43:53
    couple of years after they've passed
  • 00:43:54
    their test and car insurance companies
  • 00:43:56
    are also doing the same same kind of
  • 00:43:58
    thing so why is it that adolescents are
  • 00:44:00
    particularly susceptible to peer
  • 00:44:03
    influence well one possibility that we
  • 00:44:06
    have been looking into is that
  • 00:44:08
    adolescents might be hypersensitive to
  • 00:44:10
    being excluded by their peer groups they
  • 00:44:12
    might be really worried about being
  • 00:44:16
    ostracized by their peer group and we
  • 00:44:18
    did an experiment a few years ago
  • 00:44:20
    looking at the effect of social
  • 00:44:22
    exclusion in adolescents and this was an
  • 00:44:26
    experiment using cyber ball which is
  • 00:44:28
    this kind of online bull throwing game
  • 00:44:31
    so you're you're told so this is you
  • 00:44:33
    down here and you're going to be you're
  • 00:44:35
    going to be playing game of catch over
  • 00:44:37
    the Internet with these two other
  • 00:44:38
    players in fact that's just a cover
  • 00:44:40
    story there are no other players and we
  • 00:44:42
    program those other two players either
  • 00:44:44
    to include you in the game of catch or
  • 00:44:46
    to exclude you and this looks this we
  • 00:44:49
    did this experiment many years ago when
  • 00:44:52
    people were like wow that's so cool you
  • 00:44:55
    can play a game of catch with people
  • 00:44:57
    over the internet now I don't think
  • 00:44:58
    anyone would believe that this is a real
  • 00:45:00
    game you can do something so much more
  • 00:45:02
    sophisticated on your own phone okay
  • 00:45:04
    this is what an exclusion condition
  • 00:45:06
    looks like so you get thrown the ball
  • 00:45:09
    you can decide who to throw it back to
  • 00:45:11
    and they could throw it back to you
  • 00:45:12
    these are the players
  • 00:45:13
    but in this case they don't they just
  • 00:45:15
    continue playing with each other for
  • 00:45:16
    about two minutes and that makes you
  • 00:45:18
    feel really sad it that decreases mood
  • 00:45:24
    and increases anxiety in adults so with
  • 00:45:27
    cat Sebastian who was my PhD student
  • 00:45:30
    many years ago she now runs her own lab
  • 00:45:32
    at Royal Holloway we wondered what would
  • 00:45:34
    happen
  • 00:45:34
    to adolescents if they took part in this
  • 00:45:37
    task and I'm going to go through the
  • 00:45:39
    results so these are the results in the
  • 00:45:41
    adult group this is their mood as
  • 00:45:44
    measured by a standardized mood
  • 00:45:46
    questionnaire sorry at baseline so
  • 00:45:50
    that's the yellow before they taken part
  • 00:45:52
    in the experiment and after being
  • 00:45:54
    included in that game of catch that's
  • 00:45:56
    shown in green and then after being
  • 00:45:59
    excluded that's shirt that's their mood
  • 00:46:01
    and blue so the adults that took part in
  • 00:46:03
    our experiment showed a significant
  • 00:46:04
    decline in mood after being after being
  • 00:46:08
    socially excluded which is what other
  • 00:46:10
    people had already found and the
  • 00:46:11
    adolescent group so we tested a group of
  • 00:46:14
    11 to 14 year olds here and a group of
  • 00:46:17
    14 to 16 year olds they both showed the
  • 00:46:19
    same pattern of results as the adults
  • 00:46:21
    but their drop in mood was significantly
  • 00:46:24
    greater than the adults so what this
  • 00:46:27
    suggests is that adolescents are
  • 00:46:29
    hypersensitive to to being socially
  • 00:46:33
    excluded so what does this mean for
  • 00:46:38
    adolescent behavior well if you think
  • 00:46:41
    about if you think about this
  • 00:46:44
    hypersensitivity to social exclusion and
  • 00:46:47
    the need to avoid being socially
  • 00:46:49
    excluded to avoid what you might call
  • 00:46:51
    taking a social risk it sheds adolescent
  • 00:46:55
    typical behavior in a more rational
  • 00:46:57
    light so one of the questions I'm often
  • 00:47:00
    asked by teachers or parents is why a
  • 00:47:02
    perfectly kind of intelligent and
  • 00:47:04
    educated young person might make a
  • 00:47:06
    decision like try a cigarette when they
  • 00:47:09
    know all about the health risks of
  • 00:47:11
    smoking but if you think about the
  • 00:47:12
    situation in which most young people do
  • 00:47:14
    that kind of take that kind of risk it's
  • 00:47:16
    when they're with their friends so if
  • 00:47:18
    you if you imagine a you know a thirteen
  • 00:47:19
    year old who is out with her friends at
  • 00:47:22
    the weekend and they offer her a
  • 00:47:23
    cigarette
  • 00:47:24
    what for her is the more risky decision
  • 00:47:26
    saying yes to a cigarette when she knows
  • 00:47:28
    all about the health risks of smoking or
  • 00:47:31
    saying no and potentially being
  • 00:47:33
    ostracized by her peer group well we
  • 00:47:35
    would argue that that social risk weighs
  • 00:47:37
    in much more heavily for young people
  • 00:47:40
    because they're driven to affiliate with
  • 00:47:42
    their peer group and to be included by
  • 00:47:45
    their peer group now that's not to say
  • 00:47:46
    that it's a good idea
  • 00:47:48
    but it's it sheds those kinds of
  • 00:47:50
    adolescent typical behaviors in a more
  • 00:47:52
    rational light but I wanted to end by
  • 00:47:55
    showing that we're all influenced by
  • 00:47:58
    other people so if you can get back onto
  • 00:48:00
    your phones and again go to mentee calm
  • 00:48:08
    and Ross if you could go to the fourth
  • 00:48:12
    question okay so without any discussion
  • 00:48:21
    this is really hard just have a think
  • 00:48:24
    about this what the circumference of the
  • 00:48:27
    London Eye is
  • 00:48:39
    okay I think we're going to move on so
  • 00:48:41
    don't ruff don't show the results yet if
  • 00:48:44
    you just go on to the next question now
  • 00:48:47
    in small groups so in groups of like
  • 00:48:50
    four or three or four or five just next
  • 00:48:52
    to you it's exactly the same question
  • 00:48:55
    discuss for 45 seconds only how the
  • 00:49:01
    circumference of the London Eye
  • 00:49:42
    okay now you need to vote again
  • 00:49:48
    stop talking and vote again so each of
  • 00:49:50
    you should vote again and you're not
  • 00:49:56
    allowed to google it obviously okay
  • 00:50:03
    everyone needs to vote again in each
  • 00:50:06
    individual person needs to vote again
  • 00:50:07
    we're just like add up to about 200 I
  • 00:50:10
    think that was the last one
  • 00:50:16
    okay so Ross if you could go back to the
  • 00:50:19
    previous question and show the results
  • 00:50:22
    from that all over the place okay I can
  • 00:50:29
    tell you that the real the true answer
  • 00:50:31
    is 424 which actually I think got the
  • 00:50:33
    least the least number of votes and okay
  • 00:50:39
    so that was when you were not discussing
  • 00:50:41
    I have no idea but this is gonna work by
  • 00:50:43
    the way um Ross can you show the results
  • 00:50:46
    of the next question anyway the main
  • 00:50:53
    point here is to show it doesn't matter
  • 00:50:56
    about the actual results but to show how
  • 00:50:58
    we are influenced by other people we are
  • 00:51:01
    all influenced by others everything we
  • 00:51:03
    do if we do it when we're with other
  • 00:51:05
    people is slightly different comparable
  • 00:51:07
    with when we do it on our own we are our
  • 00:51:11
    behaviors change when we're in groups
  • 00:51:13
    removing crowds our cognitive
  • 00:51:16
    performance for example is different if
  • 00:51:18
    we're being observed by someone else
  • 00:51:21
    compared with when we're not being
  • 00:51:22
    observed and new perhaps experience that
  • 00:51:24
    just now just discussing things with
  • 00:51:26
    other people makes you think differently
  • 00:51:28
    about about questions and about
  • 00:51:30
    decisions so I'm going to end there just
  • 00:51:33
    to say that Stanley Hall when he first
  • 00:51:37
    described this period of court that he
  • 00:51:39
    called adolescence um
  • 00:51:40
    described it in a very kind of rich
  • 00:51:43
    broad way he talked about things like
  • 00:51:45
    indifference lethargy and melancholy
  • 00:51:47
    energy and exuberance he talked about
  • 00:51:51
    adolescents reflecting a combination of
  • 00:51:54
    uninhibited childish
  • 00:51:55
    selfishness and an increasing idealism
  • 00:51:59
    in virtue and although many of his
  • 00:52:00
    stereotypes have just been dismissed as
  • 00:52:03
    caricatures he was right I think to
  • 00:52:05
    highlight the importance of friendships
  • 00:52:07
    and peer influence in adolescence as
  • 00:52:09
    well as the urge to explore the world
  • 00:52:11
    with curiosity and energy and to
  • 00:52:13
    experience novelty these are
  • 00:52:15
    characteristics that are the focus of
  • 00:52:17
    much of today's research on the
  • 00:52:19
    adolescent brain um to end I want to say
  • 00:52:23
    that the adolescent brain isn't broken
  • 00:52:25
    we shouldn't think of it as a kind of
  • 00:52:26
    dysfunctional or defective
  • 00:52:28
    adult brain it's a formative period of
  • 00:52:31
    life when the brain is changing in
  • 00:52:33
    really important ways and we shouldn't
  • 00:52:35
    demonize it we should understand it and
  • 00:52:37
    nurture it and support adolescents and
  • 00:52:40
    celebrate adolescence um when a few
  • 00:52:43
    years ago I had an amazing opportunity
  • 00:52:45
    to work with the what was then called
  • 00:52:47
    the Islington community theater they're
  • 00:52:48
    now called company three a group of a
  • 00:52:50
    very big group of young people it's a
  • 00:52:52
    youth theatre company in Islington and
  • 00:52:55
    they were writing and performing a play
  • 00:52:57
    called brainstorm which was their
  • 00:53:01
    interpretation of the science of the
  • 00:53:03
    teenage brain and this had ended up
  • 00:53:05
    having two runs at the National Theatre
  • 00:53:07
    to a critical acclaim and we're very
  • 00:53:09
    lucky to have one of the stars of
  • 00:53:11
    brainstorm here Yaman Chowdhury and I'm
  • 00:53:14
    going to sit down while he gives his
  • 00:53:17
    main soliloquy from brainstorm
  • 00:53:22
    [Applause]
  • 00:53:32
    you say to me your brain is broken it's
  • 00:53:38
    like an adult's brain but it doesn't
  • 00:53:41
    work properly you say when you become a
  • 00:53:45
    teenager something happens your brain
  • 00:53:48
    shrinks or something it stops working
  • 00:53:51
    properly
  • 00:53:51
    it gets so full of thinking about
  • 00:53:53
    yourself that you forget about anyone
  • 00:53:56
    else it's like you're in a city you've
  • 00:53:59
    never been to and you don't have a map
  • 00:54:01
    and you don't know what you're doing and
  • 00:54:03
    you keep taking the wrong turns you say
  • 00:54:09
    listen to me
  • 00:54:11
    don't worry one day you'll be okay
  • 00:54:14
    probably your brain will start working
  • 00:54:18
    properly one day your brain will be just
  • 00:54:22
    like mine and then you'll be okay
  • 00:54:25
    but until then you've got to try and be
  • 00:54:27
    more like me I say to you my brain isn't
  • 00:54:36
    broken it's beautiful I'm in a city I've
  • 00:54:42
    never been to and I see bright lights
  • 00:54:44
    and new ideas and fear an opportunity
  • 00:54:48
    and a thousand million roads all lit up
  • 00:54:51
    and flashing there are so many places to
  • 00:54:54
    explore but you've forgotten that they
  • 00:54:56
    exist because every day you walk the
  • 00:54:58
    same way with your hands in your pockets
  • 00:55:00
    and your eyes on the floor I say my
  • 00:55:05
    brain isn't broken it's like this for a
  • 00:55:08
    reason I'm becoming Who I am and I'm
  • 00:55:13
    scared and you're scared because who I
  • 00:55:17
    become might not be who you want me to
  • 00:55:20
    be or who you are and I don't know why
  • 00:55:25
    but I don't say it's all going to be
  • 00:55:27
    okay
  • 00:55:27
    there are so many things I stop saying
  • 00:55:30
    to you I want to say them but I don't I
  • 00:55:36
    pick up my
  • 00:55:37
    wait put in the kitchen and go upstairs
  • 00:55:42
    thank you
  • 00:55:43
    [Applause]
ุงู„ูˆุณูˆู…
  • teenage brain
  • adolescence
  • identity formation
  • risk-taking
  • peer influence
  • brain development
  • culture
  • society
  • social behaviour
  • neuronal changes