Casey et al. (2011) Neural correlates of delay and gratification Area: Biological Theme: Regions of the brain

Key term: Delay of gratification The ability to resist temptation for an immediate reward and wait for a later reward https://m.youtube.com/watch?v=Yo4WF3cSd9Q

HOT OR COOL?

Self-control was measured by a Go/No- Go Task Requires ppts to push a button when they see a certain stimuli, and not push a button when they see a different one. Go = push the button No/Go = don’t push it

Let’s try it! When you see a YELLOW circle, hit your desk! When you see a PINK circle, don’t do anything at all. In between each trial there will be a blank screen so you know the next one is coming

Got it? For this study, Casey made the Go/No-Go task have “hot” and “cool” stimuli (not yellow and pink circles) to see how the responses differed between them “Hot” = rewarding stimulus  happy face “Cool” = neutral or fearful faces Casey wanted to see if the low delayers would make more errors in the task with “hot” stimuli because the brain couldn’t control the response to the hot cue

The Go/No-Go Tasks Before each task, instructions appeared on the screen saying which face (male/female neutral face; fearful or happy face) was the target stimulus (Go/press button) and not to press the button for the other face (No-Go)

Ready to try it? The target stimulus is the MALE NEUTRAL face. You should hit your desk if you see this. Do not do anything if you see the FEMALE NEUTRAL face.

Now… Target stimulus (GO) = female neutral face No-Go = Male neutral face

Was that the “cool” version or the “hot” version? Now we will do the “hot” version Target stimulus (GO  hit desk) = Happy face No/Go (do not hit desk) = fearful face Ready?

And now… Target stimulus (Go) = Fearful Face No-Go = Happy face

You’ve just completed all four tasks to summarise them?

The Inferior Frontal Gyrus The Ventral Striatum Brain Area The Inferior Frontal Gyrus “desires”, “emotions”, What function has the area been associated with? “cognitive control”   Lack of delay of gratification. Impulsive behaviour Which behaviours could be associated with this area of the brain if it was ‘over-active’ in an individual. Highly controlled individual Eat it now! Take what you can immediately! What would this area ‘demand’ when faced with the option of one cookie now or ten cookies later if you don’t touch the cookie. Do not eat it, wait and we shall get 10. Smile back! What would this area ‘demand’ when faced with someone smiling warmly at you but you were told try not to smile back. Don’t smile back

Background: Eigsti (2006) showed performance on a delay of gratification task in childhood had high predictive validity for later performance Marshmallow task – Casey did not use marshmallows

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.

Method: Longitudinal Quasi experiment

IV – High delayer - resisted the cookie at 4 years old and scored very low on the self-control self reports in their 20’s and 30’s. IV – Low delayer – did not resist the cookie at 4 years old and scored very low on the self-control self reports in their 20’s and 30’s. DV: Accuracy in terms of correct/incorrect responses on the go/no- go, reaction times on this test and the fMRI activity readings.

Sample: 562, 4-year-olds from Stanford’s Bing Nursery School. 155 of the original 562 were studied in their 20s (1993). 135 of the original 562 were studied in their 30s (2003).

Experiment 1 59 (23 males and 36 females) out of 117 who were contacted by Casey et al. participated in experiment 1. These participants were categorised as high-delayers or low-delayers based on the delay of gratification task and self-control measures. 32 were considered high-delayers (12 male, 20 female). 27 were considered low-delayers (11 male, 16 female). Experiment 2 Of the 59 who participated in experiment 1: 27 (13 males and 14 females) part took in experiment 2 which used an fMRI machine (15 high-delayers and 11 low-delayers). One man was excluded from the sample for abnormally low performance.

Task Description of Task Type of data produced   Original Delay of Gratification Task (at 4 years old) One cookie now or two if you wait 10 minutes. quantitative Self-report in 20’s and 30’s Self-report containing scales. Go/No-go Task – “Cold task” Press a button (of key on keyboard) when a specified male or female face is shown. Go/no-go task – “Hot task” Press a button (of key on keyboard) when a specified happy or fearful face is shown. Which of the above were used in the fMRI scanner? Hot and Cold tasks were used in the scanner.

Experiment 1 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. The 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. 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. 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.

Experiment 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. 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 inter-trial interval ranging from 2 to 14.5s in duration (mean 5.2s). A total of 48 trials were presented per run in pseudo-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. The task was viewable by a rear projection screen and a Neuroscreen (a screen which the participants can view from the fMRI scanner. Remember an fMRI scanner is one big electromagnet, which means metal cannot be near it.) five- button response pad recorded button responses and reaction times.

Experiment 1 (Outside Scanner) Results Experiment 1 (Outside Scanner) There was no effect of delay type on the reaction times of the participants. The participants all performed with a high level of accuracy for the ‘go’ trials: Cool (99.8%) Hot (99.5%) 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.

Results Experiment 1 (Outside Scanner) 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 i.e. 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.

Experiment 2 (fMRI) As with the previous experiment, the reaction times did not differ significantly the ‘go’ trials. Overall accuracy for the ‘hot’ go/no go task was high for the ‘go’ trials with 98.2% being correct. However, there was more variable performance in the ‘no go’ trials with 12.4% of the responses being false alarms. 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 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

Experiment 2 (fMRI) 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 Resistance to temptation as measured originally by a delay of gratification task is a relatively stable individual difference that predicts reliable biases in frontal striatal circuitries that integrate motivational and control processes.