A chemical found in chocolate, tea, grapes and blueberries can improve the memory of mice, research suggests.
The Salk Institute study could lead to further tests to see if epicatechin also works on humans.
The study, published in the Journal of Neuroscience, suggests it improves blood flow in the brain - especially in combination with extra exercise.
However, nutritionists warn chocolate is high in fat and sugar, which may undo any potential benefits.
This is not the first study to find a link between 'flavanol' chemicals in certain foods and health benefits - other studies claim that cardiovascular health can be improved by including them in the diet.