One of the reasons I will not tell my kids they are "gifted" or "smart" is because research says this can actually be detrimental to kids and they perform worse. Kids do better when they are praised for effort rather than innate characteristics or labels such as "good", "smart", "talented", etc.
I like the book "Nurture Shock"--it describes the research and says not to over-praise kids or tell them how wonderful they are.