Link to biological approach
Biological Psychology assumes that all behaviour has a biological basis and a physiological origin and that all thoughts and feelings are due to genetics that we inherit from our parents.
Casey links to the biological approach, as she clearly states that a person's ability to control their impulses and resist temptation is caused by an innate biological factor, which is increased activities in certain regions of the brain.
Behaviours associated with high delayers originate from increased activity in brain regions associated with impulse control, and behaviours associated with seeking rewards originate in the ventral striatum.
This is because she found that low delayers have increased activity in their ventral striatum whereas high delayers have increased activity in their right inferior frontal gyrus.