Barkley-Levenson (Topic 2 Brain development- Neural representation of EV in adolescent brain) Flashcards
Aim
To investigate if there is a difference in neural activity between adolescent and adult brains when given risk-taking scenarios (gambles) with different expected values of outcomes of those gambles.
3 hypotheses proposed by researchers:
1) Adolescents will accept more gambled of increasing expected value than adults.
2) Ventral Striatum activation will increase in proportion to increasing expected value in adolescents.
3) Adults who behave like adolescents in terms of gambling behaviour will NOT exhibit hyperactive ventral striatum activation.
Sample
19 adult ps: 8 males, 11 females aged 25-30 (mean 27.9)
22 adolescents: 11 males, 11 females aged 13-17 (mean 15.6)
All from USA, healthy, right-handed, recruited from ads on posters and internet
Volunteer sample.
Informed consent gained from adults and parents of adolescents.
Method
Quasi experiment.
Conducted in laboratory.
IV
naturally occurring: whether pa was adult or adolescent
DV
Performance on a simple mixed gambles game and Ventral striatum activity during neural measurement by functional resonance imaging (fMRI).
Pre- experiment
Researchers collected info on each ps source and amount of spending money monthly, this may have influenced perceptions of winning & losing money between individuals.
Ps were also familiarised to fMRI environment with mock scanner.
Background: Brain development
Much of our brain development happens prenatally- born with all brain structure.
Structure is hierarchical, develops in “bottom up” fashion.
Primitive structure essential for survival is developed first, matures quickly in first few months of life.
More advanced areas toward front of brain take longer, continue to develop in adolescence.
Development begins at conception continuing until about 25; brain continues to age during adulthood & old age.
Procedure
Each ps given $20 to use as ‘playing money’ during fMRI task.
Informed about opportunity to win up to $20 more, but there was also possibility they would lose it.
Ps had to decide for each trial whether to gamble for their money.
Told one of trials they accepted would be selected and played at end of scan for REAL money and outcome would be added or subtracted from overall $20 payment; encouraged ps to risk take as normally would.
Procedure- one week later
In the tasks ps were presented with series of gambles across 144 trials.
Saw spinner on screen with 50% probability of gaining amount shown on one side and 50% losing amount shown on other side.
Loses ranged from -$5 to -$20 and gains from +$5 to +$20.
In each spin/trial ps had to decide if they wanted to gamble for real money as ps we’re told one of gambles said they were willing to play would be played and they would keep outcome, gain/loss from original $20.
Expected value
The amount of risk (whether it was high gain but high loss)
Differences in brain activity would reveal…
If adolescents and adults consider risk differently.
Amount of risk (high loss/gain or low loss/gain) or expected value- may affect level of brain activity too.
fMRI scans
Neural data was collected using fMRI scanners focusing on Ventral Striatum (reward area of brain)
Behavioural responses of acceptance and rejection of each trial was recorded when ps pressed computer screens.
Final result sample
3 ps excluded as outliers left 20 adolescents and 17 adults included in results
Results from fMRI scans
Data showed MORE activation of the central striatum in ADOLESCENTS as EV increased.
Results of adolescents accepting gambles
The higher the amount that could be won, more likely adolescents accepted gamble.
Results Left Ventral Striatum (adolescents)
Adolescents showed significantly MORE activity in LEFT ventral striatum as amount available to win increased.
Results Right Ventral Striatum
(Adolescents)
Right VS showed GREATER activity in adolescents.
Results Adults vs Adolescents
Behaved similarly when there was NO risk involved in the gambles.
Conclusions
Due to brain development adolescents more likely to engage in advantageous risk- taking.
Significant developmental differences found in VS- showed adolescents greater activation in area than adults.
Researchers concluded adolescents place greater value on rewards than adults.
May mean more positive emotions & motivations occur in adolescents when making risky choices that, when rewarded, can cause them to maintain risky behaviour (operant conditioning)
Brain undergoes significant changes during adolescence- influences reward sensitivity and risk-taking behaviour (particularly gambling)
Evolutionary explanation (conclusion)
In explanation is that it offers adolescents evolutionary advantage- more willing to accept risk of advantageous gambles may help develop increased independence, becoming more independent, able to find potential mates.
(Risk-taking aids learning in life)
Psychology as a science
This research supports psych as a science.
fMRI scanner to identify active brain areas is objective and scientific tool for measuring.
In this study used number of controls to eliminate possible extraneous variables; e.g all ps right handed, screened for health, no brain abnormalities, gambling task was replicable.
Controls sought to ensure any differences in gambling behaviours and neural activity were due to age alone.
Usefulness
Finding out about neurological change in adolescent brains can help psychologists understand typical patterns of behaviour in development.
In this case hypersensitivity to rewards may explain relationship between adolescents and risk-taking behaviour.
Finding out why behaviours occur is useful as practical applications can be developed to modify particular behaviour.
Usefulness- sample (limits usefulness)
Only 19 adults and 22 adolescents in US studied.
Sample lacked pre-adolescence group (8-12 years old) meaning researchers unable to track developmental changes in neurological activity.
Found neurological differences in VS activation in adolescents in comparison with adults, but it’s unclear when these differences actually begin to develop.
Ecological validity
Lacks ecological validity.
Ps subjected to fMRI scan to measure brain activity whilst taking part in gamble task; not usual occurrence in everyday life.
Gave money to use in gambling task, unlike real life; usually use own money, experiencing real stress/euphoria from losses or gains.
Task may have been unrealistic for adolescents who would be less likely to engage in such activities , due to age restrictions on gambling.
So task and results do not really represent actual risk-taking behaviour.
Nature/Nurture
Supports nature side, biological features cause us to behave certain ways, i.e hyperactive VS causes risk-taking behaviour.
Nurture side of argument argues graduated driver licensing schemes for parental interventions can educate adolescents, reduce such behaviour (supports nurture)
Peer groups and social environment situations that young people find themselves in can influence risk-taking behaviour like drinking, rather than just nature.
Determinism
Explaining risk-taking behaviour in terms of brains of adolescents=biologically deterministic; assumes all adolescents behave particular way because of development of VS.
Fails to consider environmental factors (reductionist).
Albert et al 2013- argues due to nature of adolescent brain, individuals are vulnerable to risk-taking behaviour and highly sensitive to rewards provided by friends.
Probability of risk taking is high, but situations exposed to and interactions with their peers triggers behaviour.
Therefore, risk-taking is due to interaction between individual and situational explanations (holistic approach).
Methodological issues
Apply to lab-based research;
validity due to high controls, lack of ecological validity, reliability and ethics involved in taking part in risk-taking behaviour tasks.
