Casey (2011) Flashcards
Background
Research by Metcalfe and Mischel (1999) proposed two interactive neurocognitive systems to explain resistance to temptation.
They suggested that there is a ‘cool’ system which involves cognitive control-related neutral circuitry, located in the prefrontal cortex.
Aim
To build upon previous research which assessed whether delay of gratification in children predicts impulse control abilities and sensitivity to alluring or social cues (happy faces in this study) at the both the behavioural and neural level when the participants were in adulthood.
Procedure
Independent variable: high delayer or low delayer. (This was naturally occurring, as the participants early in the study were found to delay gratification frequently (high delayers) or not very often (low delayers).
Dependent variables: Performance on an impulse control task (go/no go task, see above). This was measured in terms of reaction times and accuracy. Imaging from an fMRI scanner was also measured
Sample
562, 4-year-olds from Stanford’s Bing Nursery School.
High/Low Delayer
High = Good self control
Low = Poor self control
Experiment 1 Procedure
Tested whether individuals who were less able to delay gratification as children and young adults (low delayers) would, as adults in their 40’s, 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” (i.e. target) stimulus to which participants were instructed to press a button, and the other sex as a “no-go” (i.e. non-target) stimulus to which participants were instructed to withhold a button press.
Experiment 2 Procedure
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 increased 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 intervals ranging from 2 to 14.5 seconds in duration.
A total of 48 trials were presented per run in randomised order (35 go, 13 no-go).
In total, imaging data were acquired for 26 no-go trials and 70 go trials for each expression.
Experiment 1 Findings
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 decrease 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 i.e. individuals, who as a group, had more difficulty delaying gratification at 4 years of age (low delayers) showed more difficulty as adults in
suppressing responses to happy faces than the high delayers.
Experiment 2 Findings
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 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 that 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
Environmental hot cues play a significant role in an individual’s ability to suppress actions toward tempting cues
Resistance to temptation as measured originally by a delay-of-gratification task is a reliable predictor of future behaviour
The capacity to resist temptation varies by context, the more tempting the choice for the individual, the more predictive their delay of gratification
Individuals who, at the age of 4 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.
