Casey Flashcards
key theme + area
key theme =
area =
background
- delay of gratification - ability to something enjoyable off in order to wait for something better
- Stanford marshmallow experiment
- some children high delayers some low
hot and cold system in brain
- hot = ventral striatum, in the limbic system is associated with rewards
- cold = cognitive control, deciding whether to resist or not
fMRI scan
(Functional magnetic resonance imaging or functional MRI (fMRI))
- its a functional neuroimaging procedure using MRI tech that measures brain activity by detecting changes associated with blood flow
- when brain area in use, blood flow to that region increases
aims
to find out if ppts who were low delayers on the Marshmallow Test at age four, and who also reported low self-control on psychometric measures in their twenties + thirties would.
sample
ppts chosen from group of ppts who were all born between 1964 and 1970 and had been tested at age 4 on the Marshmallow Test and also completed tests of
self-control on a self-report inventory in their twenties (in 1993) and thirties (in 2003).
- The possible sample size had reduced from 562 in the original study to 59 participants who agreed to be tested in this study.
The 59 PPTs consisted of:
> 27 Low Delayers (16 females, 11 males)
> 32 High Delayers (20 females, 12 males).
method
longitudinal design
experiment 1 - procedure
- All 59 PPTs tested
- Self control measured by a Go/No Go Task
- PPTs each did four Go/No Go tasks.
- complete the task on a laptop sent to their home
- The tasks involved a series of faces (male or female neutral face, fearful or happy) being shown on the screen of a laptop. Each face appeared for 500 ms, with a 1s interval between faces.
- Before each task, instructions appeared on screen saying which face was the target (Go) stimulus. PPTS were told to press a button for the target face (Go) and not press the button for the other face (No Go)
- PPTs were told to respond as quickly and accurately as possible
go/no go tasks
- ‘Cool’ Version – press the button whenever the male neutral face appeared, which it did 120 times out of 160 faces. Male face- go- Female face No go
- ‘Cool’ Version – press the button when the female neutral face appeared, which it did 120 times out of 160 faces. Male face- no go- Female face go
- ‘Hot’ Version – press the button whenever a happy facial expression appeared, which it did 120 times out of 160 faces
- ‘Hot’ Version – Press the button whenever a fearful face appeared, which it did 120 times out of 160 faces
experiment 1 - results
- both groups of ppts performed high level of accuracy on go trials in both cool + hot versions
- Both groups made more errors on the No-Go tasks, which Casey interpreted as ‘false alarms’, However whereas they made a similar number of errors on the ‘cool’ task, the low delayers made more errors on the ‘hot’ task overall.
- The low delayers made the same number of errors as the high delayers on the ‘fearful’ face No-Go trials
- However the low delayers made more errors than the high delayers on the happy face No-Go trials.
experiement 1 - conclusions
Low Delayers who had shown more difficulty in delaying gratification at age 4 showed more difficulty suppressing their responses to happy faces in their 40s.
- These findings suggest that low self-control remains
consistent in an individual over time.
- The findings also show that this depends on the rewarding nature of the stimulus in the task, as the low delayers had more difficulty only on the happy face ‘hot’ task than the high delayers.
sample + aim of experiment 2
- In the second experiment Casey et al aimed to investigate the regions of the brain that they predicted would be implicated in self-control with use of an fMRI scanner.
Sample - 26 of the 59 PPTs used in Study 1 were tested while in an fMRI scanner.
- Of these 15 were high delayers (10 female and 5 male)
- 11 were low delayers (4 female and 7 male)
experiment 2 - procedure
- The PPTs each took part in a similar ‘hot’ Go/No-Go task and experiment 1.
- The task differed from the first experiment in that:
- Instead of a 1s delay between the presentation of faces, there was a 2- 14.5 second delay (mean 5,2s) where ppts rested while viewing a fixation crosshair
- There were 48 trials per run, 35 ‘Go’ and 13 ‘No-Go’, giving a total of 70 ‘Go’ and 26 ‘No Go’ trials for each expression, fearful and happy.
- Although the stimuli and instructions were identical to experiment 1, the apparatus was different as the stimuli were presented on a screen in the scanner and a different type of push button apparatus was used for responses.
experiment 2 - results
- Both groups scored highly in accuracy for the ‘Go’ trials and the low delayers showed more false alarms (low delayers 14.5% and high delayers (10.9%)
- The imaging (fMRI) results showed two main differences between the high and low delayers.
- The low delayers showed lower activity in the inferior frontal gyrus than the high delayers in the No-Go trials. Casey et al concluded that this suggests that this brain region plays an important role in the with-holding of a response,
- The low-delayers showed higher activity in the ventral striatum, especially when the ‘happy’ faces were the No-Go stimuli. This suggests the ‘hot’ features of this stimulus made this reward-related region more active and made it harder for the ppts to ‘resist’, resulting in more errors.
conclusions
“Sensitivity to environmental cues influences an individual’s ability to suppress thought and actions, such that control systems may be ‘hijacked’ by a primitive limbic (emotional) system, rendering control systems unable to appropriately modulate behaviour” (Casey et al)
- low delayers showing less recruitment in the inferior frontal gyrus + exaggerated recruitment in the ventral striatum when trying to resist alluring cues
