Contemporary study: Casey et al. (2011), Behavioral and neural correlates of delay of gratification. Aim, method, results and conclusions, evaluation, and links to the biological area and Sperry.

A description item testing method and results (AO1).

Method: a longitudinal follow-up of participants first tested as 4-year-olds in Mischel's marshmallow studies, now adults in their 40s. They were classified as high or low delayers based on their childhood self-control. In Experiment 1, about 59 participants did a behavioural go/no-go task with social cues (happy and neutral or fearful faces), responding to one type and withholding to another, to test impulse control. In Experiment 2, a subset of 26 did a similar go/no-go task (using happy and neutral faces) in an fMRI scanner so brain activity could be measured.

Results: high delayers performed better on the no-go trials (better at suppressing a response), especially when the cue was a tempting happy face. The fMRI showed that low delayers had higher activity in the ventral striatum (linked to reward) to the tempting cues, while high delayers showed greater activity in the inferior frontal gyrus (right prefrontal cortex, linked to impulse control). Self-control appeared stable from childhood to adulthood and was reflected in distinct patterns of brain activity.

Markers reward the longitudinal Mischel follow-up, the go/no-go task with social cues, the fMRI in Experiment 2, and the key results (high delayers better at no-go; prefrontal versus ventral striatum activity differences).

Tests interpretation plus evaluation (AO1 and AO3).

What it tells us: the ability to delay gratification is relatively stable across life and is associated with distinct brain activity, greater prefrontal (inferior frontal gyrus) activity in high delayers, who control impulses, and greater reward-related ventral striatum activity in low delayers. This supports a biological basis for individual differences in self-control.

Strengths: the longitudinal design over about 40 years gives rare, valuable evidence on the stability of a trait; the fMRI provides objective, quantitative data on brain activity; and the controlled go/no-go task isolates impulse control.

Weaknesses: the fMRI sample was small (26), limiting generalisability; brain activity is a correlate, so it cannot prove the brain region causes self-control rather than reflecting it; and the lab task is artificial compared with real-world temptation.

A strong answer concludes that the study gives strong correlational evidence linking self-control to specific brain regions and shows trait stability, but cannot establish causation and uses a small imaging sample. Markers reward the biological interpretation plus balanced evaluation.