Blueberries contain a lot of things that are good for the body, including antioxidants and flavonoids which are thought to be what is responsible for improving memory as well as other things like preventing heart disease and certain cancers.
There has been a lot of research done into these berries and it has been concluded through numerous studies that they can in fact improve memory substantially. The flavonoids in blueberries are absorbed in the blood stream and therefore are able to provide those who consume them with numerous health benefits, including the ability to better fight off infections which enter the body.