Compositions include arginine and one or more unsaturated fatty acids. Methods for using such compositions can enhance cognitive function, reduce or prevent a decline of social interaction, reduce or prevent age-related behavioral changes, increase trainability, maintain optimal brain function, facilitate learning and memory, reduce memory loss, retard brain aging, prevent or treat strokes, and/or prevent or treat dementia in an animal. Preferably, the compositions are food compositions useful for enhancing cognitive function in humans and companion animals.