Alexis Martin, from Queen Creek in Arizona, began reading at the age of two and has since taught herself Spanish using her parents' iPad.
Her dad, Ian, told ABC News that she Alexis had her IQ tested, scoring the maximum number of points – 160, the same as Albert Einstein and Stephen Hawking.
Alexis is now the youngest member of her Arizona Mensa chapter and can read at fifth-grade level (when students are between ages 10-11).
Her parents filmed her identifying all the continents and countries they gave her, and said that they desperately wanted to retain her childhood as much as possible.
Ian said: "Anytime she learns a word and just picks it up through anything, she never ever uses it in the incorrect context."
Mensa admits people with an IQ in the top two per cent of the population (the average being an IQ score of 100) and has 110,000 members around the world in 100 countries.
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