B - Casey Flashcards
Sample
All ppts were chosen from a group of ppts who participated in the original experiment when they were 4 in Bing University nursery, Stanford
There were 562 ppts!
In 1993 when the ppts were in their 20s, they completed a self-control self-report survey. 155 of the original sample did this.
Then, in 2003, 135 of these ppts did another self-control inventory.
This identified low delayers (those who scored consistently low on measures of self control) and high delayers (those who scored consistently high on measures of self control)
60 were classed as low and 57 high. These 117 ppts were then contacted
59 then agreed to be tested. (36 females and 23 males)
In this sample of 59, there were 27 low delayers (16 F and 11 M) and 32 high delayers (20 F and 12 M)
Aim
To find out if ppts who were low-delayers on the marshmallow test at age 4 also reported low self-control in their 20s and 30s
Background
Previous research (Eigstl, 2006) showed performance on a delay-of-gratification task in childhood predicted the efficiency with which the same individuals performed a cognitive control task (go/nogo task) as adolescents and young adults. Those who as preschoolers directed their attention toward rewarding aspects of the classic delay-of-gratification situation, such as focusing on cookies (high-temptation-focus group) had more difficulty suppressing inappropriate actions than did their low-temptation-focus counterparts. The findings suggested that performance in preschool delay of gratification may predict the capacity, in adulthood, to control thoughts and actions, as reflected in performance on cognitive control tasks, and that the ability to control one’s thoughts and actions can vary by the potency of interfering information (Shoda et al, 1990). Likewise, alluring or social contexts can diminish self control (eg Hare et al, 2005).
The aim of this study was to build on previous research to assess whether delay of gratification in childhood predicts impulse control abilities and sensitivity to alluring or social cues (happy faces) at the behavioural and neural level when participants were in their 40s ie adults.
The alluring qualities of targets in an impulse control task were manipulated to examine behavioural and neural correlates of delay of gratification using functional magnetic resonance imaging (fMRI).
Method
This can be considered a quasi/natural experiment.
The Independent variable (IV)- whether the participant was a high delayer or a low delayer was naturally occurring and so could not be manipulated or controlled by the researchers.
The dependent variable (DV) was the performance on the impulse control task (in terms of reaction times and accuracy) in Experiment 1 and the performance on the impulse control task (in terms of reaction times and accuracy) and imaging results using fMRI.
The fact that some participants completed self-control scales when in their 20s and 30s and that those participating in Experiment 1 did both the “hot” and “cool” go/nogo tasks means the study had, in parts, a repeated measures design.
This was a longitudinal study which followed some of the original participants from the age of four years until they were in their 40s.
Sample
562, four-year-old pupils from Stanford’s Bing Nursery School completed a delay-of-gratification task during the late 1960s and early 1970s
155 of these completed self-control scales when in their 20s (1993) and then 135 of these when in their 30s (2003). 117 of the 135 individuals who were above average or below average in their original delay of gratification performance as well as in the self report measures of self control were contacted in relation to participating in this study.
59 (23 males, 36 females) of the 117 agreed to participate in this longitudinal behavioural study (Experiment 1). Participants were classified as low or high delayers from the results of (a) their delay-of-gratification performance and (b) the self-control measures. In Experiment 1 there were 32 high delayers (12 male, 20 female) and 27 low delayers (11 male, 16 female).
27 (13 males, 14 females) of the 59 who participated in Experiment 1 agreed to be part of a functional neuroimaging study (Experiment 2). In Experiment 2 there were 15 high delayers (5 male, 10 female) and 11 low delayers (7 male, 4 female) NB: One 41-year-old man was excluded from all analyses because of poor performance so results for Experiment 2 were based on the performance of 26 participants.
Procedure EXP1
This tested whether individuals who were less able to delay gratification as children and young adults (low delayers) would, as adults in their 40s, show less impulse control in suppression of a response to “hot” relative to “cool” cues.
The 59 participants, already classified as high or low delayers, consented to take part in a behavioural version of a “hot” and “cool”impulse control task.
Participants completed two versions of the go/no-go task. The “cool” version of the task consisted of male and female stimuli which were presented, one sex as a “go” (ie target) stimulus to which participants were instructed to press a button, and the other sex as a “no-go” (ie nontarget) stimulus to which participants were instructed to withhold a button press.
Before the onset of each run, a screen appeared indicating which stimulus category served as the target.
Participants were instructed to respond as quickly and accurately as possible.
Each face appeared for 500ms, followed by a 1-s interstimulus interval.
A total of 160 trials were presented per run in pseudorandomised order (120 go, 40 no-go).
The task was therefore a 2 (trial type: go, no-go) x 2 (stimulus sex: male, female) factorial design.
Accuracy and response latency data (reaction times) were acquired in four runs representing each combination of stimulus sex (male, female) and trial type (go, no-go).
The “hot” version of the go/no-go task was identical to the “cool” version except that fearful and happy facial expressions served as stimuli.
The tasks were presented using programmed laptop computers sent to participants’ homes.
Results EXP 2
Reaction times (inside the scanner)
The two delay groups did not differ significantly in reaction times in correct “go” trials: [t (24) = 0.81, P 20.4].
Accuracy (inside the scanner)
Overall accuracy rates for the “hot” go/no-go task were uniformly high for “go” trials (mean 98.2% correct hits) with more variable performance to “no-go” trials (12.4% false alarm rate).
Differences between the two delay groups in “no-go” accuracy were consistent with the observed differences in the “hot” task performance in Experiment 1, with low delayers committing more false alarms than high delayers.
Imaging results
The “no-go” vs. “go” trials identified candidate regions of the brain differentially engaged as a function of cognitive control tasks. The right inferior frontal gyrus was involved in accurately withholding a response.
Compared with high delayers, low delayers had diminished recruitment of the inferior frontal gyrus for correct “no-go” relative to “go” trials. The ventral striatum demonstrated significant difference in recruitment between high and low delayers. This reward-related region of the brain showed a three-way interaction of group x trial x emotion, with elevated activity to happy “no-go” trials for low delayers relative to high delayers.
These results showed that the prefrontal cortex differentiated between “no-go” and “go” trials to a greater extent in high delayers. The ventral striatum showed exaggerated recruitment in low delayers.
Conclusions
Sensitivity to environmental hot cues plays a significant role in an individual’s ability to suppress actions toward alluring cues. •Resistance to temptation as measured originally by a delay-of-gratification task is a relatively stable individual difference that predicts reliable biases in frontostriatal circuitries that integrate motivational and control processes.
The capacity to resist temptation varies by context, the more tempting the choice for the individual, the more predictive are the individual differences in peoples’ ability to regulate their behaviour.
Behavioural correlates of delay ability are a function not only of cognitive control but also of the compelling nature of the stimull that must be
suppressed,
Individuals who, at the age of four years have difficulty delaying gratification and who continue to show reduced self-control abilities have more difficulty as adults in suppressing responses to positive social cues than those who don’t,
Methpd evaluation - S
Point - A strength of a quasi exp – can study behaviours that it would be impossible to manipulate.
Explain – This is useful for studying how differences in brain activity effect behaviour.
Evidence - P’s – naturally a high/low delayer and so their ability to delay gratification can be studied and used to understand how this effects people’s behaviour.
Ethics
Point…The ethical guideline of protection from harm may have been raised.
Explain…P’s may have been distressed by their performance within the procedure.
Evidence…The p’s classed as low delayers may have felt distressed due to making errors on the happy no-go task. This may have made them feel inferior to high delayers and they believe they have no self control.
Reliability
Any longitudinal research has poor external reliability. Studies of this kind are difficult to replicate for practical reasons as they are not time and cost effective. If we were to repeat Casey’s study we would need to start with a group of 4 year olds and follow them through into their 40s. This is unlikely. However, the procedure is highly standardised which means this can be easily repeated. For example, in the GO/NO GO tasks, all participants were exposed to the same number of trials, same faces and for the same length of time (500ms). This means the study has high internal reliability.
Validity
Study had high internal validity as the task was pre-programmed so everyone experienced the same number of trials, same type of images flashed up for the same amount of time. This meant extraneous variables were controlled and cause and effect should be established.
However, as participants completed the task at home, extraneous variables (distractions such as other family members, tv, dog barking etc) could have affected concentration and therefore we are unsure as to whether it was these distractions that affected results or whether the fact participants were high delayers or low delayers. This reduces the internal validity of the study.
Procedure EXP 2
fMRI was used to examine neural correlates of delay of gratification. It was anticipated that low delayers would show diminished activity in the right prefrontal cortex and amplified activity in the ventral striatum compared to high delayers.
27 participants from Experiment 1 agreed (consented) to complete the imaging study.
Participants completed a “hot” version of the go/no-go task similar to that used in Experiment 1. Differences were in timing, number of trials and apparatus.
Each face stimulus was presented for 500ms, followed by a jittered intertrial interval ranging from 2 to 14.5s in duration (mean 5.2s).
A total of 48 trials were presented per run in pseudorandomised order (35 go, 13 no-go).
In total, imaging data were acquired for 26 no-go trials and 70 go trials for each expression. The task was viewable by a rear projection screen and a Neuroscreen five-button response pad recorded button responses and reaction times.
One participant was excluded for excessively poor behavioural performance on the fMRI version of the task leaving 26 participants for group analysis.
A2x2x2 group linear mixed-effects model was conducted with factors of trial type (within subjects: go no-go), emotion (within subjects:
happy, fearful) and group (between subjects: high delayer, low delayer).
Results EXP 1
Reaction times (outside the scanner)
There were no effects of delay group on reaction time measures to correct ‘go” trials [main effect of group, F(1,57)=2.23, P 20.1; group x task interaction, F= (1,57)=0.002, P≥ 0.9].
Accuracy (outside the scanner)
Participants performed with a high level of accuracy for correctly responding to “go” trials during both the “cool” (99.8% correct) and “hot”
tasks (99.5% correct). Low and high delayers performed with comparable accuracy on “go” trials. Accuracy for “no-go” trials was more variable, with low delayers
committing more false alarms than high delayers.
Low and high delayers performed comparably on the “cool” task but the low delayers trended toward performing more poorly on the “hot” task than the high delayers; only the low delay group showed a significant decrement in performance for the “hot” trials relative to the “cool” trials.
Overall therefore the go/no-go task produced differences between the delay groups only in the presence of emotional “hot” cues ie individuals who as a group had more difficulty delaying gratification at four years of age (low delayers) showed more difficulty as adults in suppressing responses to happy faces than the high delayers.
Methpd evaluation - W
Point…Less control over extraneous variables
Explain… Individual differences may not be accounted for
Evidence…There may be other differences between high/low delayers that effect the results on the ‘go-no-go’ task.
