Topic 2 - Pre-adult Brain Development

What is pre-adult brain development like?

• Irregular bursts of brain grown occur around ages 2 and 4, 6 and 8, 10 and 12 and 14 and 16 years old

• Adolescents are more prone to risk taking and impulsive behaviour such as frequent drug use, injuries/accidents, unprotected sexual activity

• The pre-frontal cortex which controls high-level reasoning and decision making is one of the last parts of the brain to develop

How do areas of the brain mediate risk taking behaviour?

• Irregular bursts of brain growth occur at different ages; between 14 and 16 years of age.​

• 2. A reason for adolescents being prone to risk taking behaviour is link to the order in which regions of the brain develop. Develops from back to front.​

• 3. The pre-frontal cortex – high-level reasoning, decision making – front of the brain – does not mature until the mid 20’s. ​

• 4. This leads younger people to ignore the negative consequences of the decisions they make.​

• 5. The ventral striatum – ‘reward centre’ develops early – encourages adolescents to engage in risky behaviour.​

  • It is highly sensitive to rewards, making adolescents sensation seeking

Because of all of this, there is an inevitable period of risk for adolescents

Outline the research method and variables of Chein’s background research

• Lab experiment

• Repeated measures design

• IV 1 - Adolescent (14-18), Young adult (19-22), Adult, (24-29)

• IV 2 - Presence of peers (alone or with 2 peers)

• DV 1 - Number of risks taken

• DV 2 - Number of crashed

• DV 3 - fMRI of brain activity

Outline the sample of Chein’s background research

• 40 participants

• 14 were adolescents, 14 were young adults, 12 were adolescents

  • The adolescents were split into 8 female and 6 male, the other two groups were split evenly between male and female

• Informed consent gained

• Participants received monetary compensation for their participation

Outline the task of Chein’s background research

• Stoplight task

• Participants do a computer-based driving task where they control the progression of a car along a straight track from the driver’s point of view

• The track has 20 intersections and participants can do 1 or 2 things:

  • They can choose the ‘GO’ option which is faster than a ‘STOP’ action but can possibly lead to a crash

  • They can choose the ‘STOP’ option which is slower than a successful ‘GO’ but is faster than if a participants chooses to go and then crashes

• The probability of a crash at each intersection was varied to be unpredictable

• Monetary incentive was given for completing the course in a timely fashion

• The participants were also in a fMRI scanner to examine brain activity during the task

How was social context manipulated in Chein’s background research

• All pps bought 2 friends along to the study​

• In an ALONE condition, participants completed the task with no observers​

• In a PEER condition, participants were informed that their friends were going to observe their actions from a monitor in the neighbouring scanner control room. In the break prior to the onset of the PEER condition, the peers were asked to communicate with the scanned pp via the scanner’s intercom system​

• In order for the interaction to be ecologically valid, the peers were permitted to speak authentically while informing the scanned participant of their presence, demonstrating their ability to observe task performance on the monitor, and communicating that they had made predictions about the scanned participant’s pending performance.

• The peers were carefully instructed to make these specific points during the interaction, and to avoid comments that might explicitly or intentionally bias behaviour

• Social context was manipulated with counterbalancing to account for order effects​

What results can we find from Chein’s background study?

• Significantly higher % of risky decisions made when peers were present for adolescents (not a significant difference for young adults and adults as the SD bars overlap)

• Greater activity in the ventral striatum in adolescents - Risky behaviours seen as more rewarding

Evaluations for Chein’s background research

• Ethical – consent gained​

• Scientific – objective (fMRI scans used), C+E (presence of peers causes more risky behaviour),

• Reliable- standardisation (all pps complete the same computer based driving task)​

• Determinism – peers determine risk taking ​

• Holistic – looks at risk taking behaviour in adolescents, young adults and adults plus explores the impact of doing the task ALONE and with PEERS​

• Situation – peers being present makes adolescents more likely to take risks​

• Nature – brain matures with age – VS fully developed but PFC is not​

• Useful – driving laws can be implemented, policy change (graduated driving licence)

Outline Anda’s background research

• Self report – Adverse Childhood Experiences (ACE) questionnaire​

• Assessed 8 ACEs​ such as abuse, witnessing domestic violence

• Questionnaire completed by 17,337 adults in San Diego​

• Increase in risky behaviours (including drug use, sexual behaviours) associated with increased number of ACE’s​

• ACE’s affect the development of the reward system

  • Risky behaviours such as drug use may be sought out in order to experience rewards from the environment

Evaluation of Anda’s background research

• Large sample (17,337) = generalisable but all from San Diego (ethno)​

• Subjective – self report (qual data) used plus issues around validity (SBD?)​

• Quant data – ACE score and % risk taking bhvr​

• Determinism – ACE determine risk taking​

• Holistic – 8 ACE are measured – doesn’t just look at one​

• Stigma – people who have experienced ACEs may experience judgment as they are expected to take risks, may be looked down upon even if they don’t partake in risky behaviours

• Situation – abuse/other ACEs increase stress which affects brain development which may lead to risk taking bhvr​

• Nurture – ACEs affect brain development ​

• Useful – social services – provide support for families/YP exposed to ACEs

What is the aim of Barkley-Levenson’s research?

• To investigate whether adolescents attach more value to rewards than adults do​

• To identify neural development of expected value (EV) in the brains of adolescents​

What does expected value mean?

EV – the sum of all the possible outcomes of a particular choice multiplied by their probabilities (effectively the average outcome of a bet)

In real life we weigh up the risk and reward by roughly taking into account all the possible outcomes

What is the sample of Barkley-Levenson’s research and how were they recruited?

• 19 healthy, right-handed adults (ages 25-30)​

• 22 healthy, right-handed adolescents (ages 13-17)​

• All participants were recruited through poster and internet advertisements in America and all participants reported no prior diagnosis of psychiatric or neurologic illness or development delays​

What were the IV and DV of Barkley-Levenson’s research?

• I.V. – AGE – Adult or adolescent = quasi experiment​​

• D.V

  • 1. Neural activity in the Ventral Striatum ​

  • 2. Behavioural responses to a gambling task​

How were participants matched in Barkley-Levenson’s research?

• All right-handed - Left hemisphere is physically larger and moredeveloped than the right hemisphere – this helped to ensure that brainfunction was the same between participants​

• Matched on income – to remove the value of monetary reward being influenced by how much they normally have to spend​

Outline the procedure of the intake session of Barkley-Levenson’s research?

• Participants initially attended the laboratory for ‘an intake session’ for neuro-imaging and to provide consent (from themselves or their parents).

• In this session they were asked about their primary source and amount of spending money per month: the mean for adolescents was $52.50; for adults it was $467.​

• Participants were given $20 for completing the intake session and were told that they would use the $20 as “playing” money during the fMRI task. Furthermore, they were told there was a chance to win up to $20 more in addition to their playing money, but they could lose it during the gambling fMRI task.​

Outline the gambling task in Barkley-Levenson’s research

• Each given $20 to use as ‘playing’ money during fMRI scan​

• Told they could win an additional $20 or lose it during gambling

• There was a 50% probability for either side of a spinner of winning the money on one side, or losing the money on the other

  • P’s had to respond within 3 seconds, with brief intervals between trials

• Had to decide whether they would ‘accept’ (gamble) or ‘reject’ (not gamble) with their $20 for each trial.​

• Told for one ‘accepted’ trial they would ACTUALLY gamble with their $20.​

• Acceptance (gamble) and rejection (no gamble) was measured by participants pressing a certain key on the keyboard.

Why was an MRI used in Barkley-Levenson’s research?

• To measure the activity in the ventral striatum (VS) as this area is associated with valuation and reward.​​

• The brain scan was conducted whilst they completed the task​

• Compare the level of activity between adults and adolescents during the task.​

When does the expected value increase in the gambling task?

When there is more to gain on one side and less to lose on the other

What results can we find from Barkley-Levenson’s study?

• Adolescents showed hyperactive reward sensitivity, they pay more attention to what they can win than what they can lose

• The higher the EV (higher likelihood of winning), the more likely the adolescent was to gamble in comparison to the adult. This suggested that adolescents focus more on the higher amount they could win, and less concerned with the relatively smaller amount they stood to lose.​

• Both adults and adolescents, virtually never accepted gambles with negative EV (i.e. more to lose, less towin). This shows that adolescents were equally capable as adults in avoiding disadvantageous choices.

• The fMRI data showed more activation of the VS in adolescents as the EV increased compared to adults.

  • Even when gambling behaviour was similar across both groups, VS activation was still greater in adolescents.

What conclusions can be drawn from Barkley-Levenson’s study?

• Adolescents place greater value on rewards than adults do​

• Neural representations of value in adolescents’ ventral striatum are linked to increased risk taking behaviour.

What applications do we have for risk taking behaviour in adolescents?

• Graduated driver licensing schemes

• Black boxes fitted in cars

• SLT and behaviourist perspective

How can we apply graduated driver’s license schemes?

• Aims to reduces risk taking behaviours whilst driving (eg speeding, driving with peers, driving under the influence) to reduce number of road traffic accidents ​

• GDL schemes vary depending on country, but the main premise is to have a period of probation for newly qualified drivers​

• Restrictions include: limits on the number of passengers, limits of alcohol consumption, limits on night time driving (no driving between 10pm-5am) for eg​

• Mobile phone use can also carry heavier penalties for newly qualified drivers​

Study to support the use of graduated driver’s license schemes?

Chein

How can we apply black boxes fitted in cars to applications to reduce risk taking behaviour in adolescents?

• The black box device records a cars speed, the distance it travels, how it accelerates and brakes, and what time of the day or night the car is used – all of this info builds a profile of the driver so that insurance companies can assess the risk of the driver ​

• Drivers are able to save money on their yearly insurance cover if they are deemed to ‘drive sensibly’​

• Drivers are incentivised to drive sensibly so that ultimately they prevent something undesirable from happening (more money to pay) – eg of negative reinforcement ​

How can we applying SLT and the behaviourist perspective to reducing risk taking behaviour for adolescents?

Positive role models

• Young people need to be provided with positive role models that they can learn from and imitate. ​

• Therefore if young people see that their parents are driving in a safe and secure manner [or any other risky behaviour], they will be likely to learn and imitate this behaviour

Positive reinforcement

• Young people can be provided with a reward when they partake in ‘non risky behaviour’, such as academic success to encourage them to continue with this behaviour and avoid partaking in risk taking behaviours instead​

What studies can we use to support the use of SLT and the behaviourist perspective in reducing risk-taking behaviour in adolescents?

• SLT- bandura

• Behaviourist perspective- Chaney