A 2-year-old girl from Crestwood, Kentucky, has amazed everyone by becoming the youngest female member of Mensa, the world's oldest high IQ society.

Mensa International is a non-profit organization for people who score at the 98th percentile or higher on a standardized IQ test. It is the world's largest and oldest high IQ society.

Isla joined the organization after scoring in the 99th percentile for intelligence for her age on the Stanford-Binet Intelligence Scales.

Isla's parents noticed that she had a very focused attention from the moment she was born.

While she was clearly very intelligent, nothing seemed strange until she started learning.

At just one-year-old, Isla started learning her colours, numbers, and the alphabet.

"At seven months old, she would pick out certain items from picture books when asked," said Isla's father, Jason McNabb.

At 18 months, she learned the alphabet on her own and began to read at two years old.

On her second birthday, Isla's aunt Crystal gave her an erasable writing tablet.

Jason wrote the word "red" on the tablet, and Isla was surprisingly able to read the word.

Both Jason and Isla's mother, Amanda, were shocked.

Jason then proceeded to write the words "blue," "yellow," "cat," and "dog," which Isla read aloud without hesitation.

Isla's parents would also find multicoloured toy letters next to objects around the house.

Next to a chair, they found the letters C-H-A-I-R, and next to the couch, they found the letters S-O-F-A.

Even their cat Booger was found with the letters C-A-T next to him.

It was then that Amanda suggested they get Isla tested.

At two and a half years old, Isla scored in the top 1% of the population, qualifying her for a Mensa membership.

"A psychologist who tested Isla specializes in gifted children," said Jason.

"He said he usually doesn't test children as young as two, but made an exception after hearing about her talents."

Amanda and Jason quickly discovered that there are very few resources for gifted children.

By enrolling Isla in Mensa, their goal was to gain some information from other parents of gifted children.

"The biggest benefit to Mensa is the community," said Jason.

The parents of other gifted children have been a valuable source of information.

Isla, who is now three years old, is currently enrolled in preschool.

Her parents hope to get an individual education plan for her to be able to start kindergarten early.

Isla loves learning and while she is above average in multiple subject areas, she is especially strong in maths and excels at reading.

She continues to surprise her parents with the knowledge she soaks in.

"She often mispronounces words that we can only assume she learned by reading," said Jason.

"Last week she said she needed to wash the germs off her hands but pronounced it with a hard G."

Isla also began to show her parents the alphabet in American Sign Language, and they are still trying to figure out where she learned it.

However, Jason says there are some difficulties when it comes to raising such a bright child and that there has been a learning curve.

"With my other children, if I didn't want them to know what I was talking about, we could just spell things out in front of them, but Isla picks it up right away," he said.

If I ask her mother 'Hey, should we get an I-C-E-C-R-E-A-M', Isla will perk up and yell 'ice cream!'

Jason also says that some aspects of Isla's personality are typical of her age, and some are so advanced that it has been difficult for her to reconcile the two.

"Isla thinks she is on par with adults, and it can be challenging," said Jason.

"She never settles for 'because I said so.'"

In her free time, she enjoys drawing, school, and playing with Booger.

Isla also loves to read books, with The Very Hungry Caterpillar and Pete the Cat books being among her favourites.

She has seen herself on television and sometimes asks to watch herself on YouTube, but has not yet realized how unique she really is.

Her friends are also too young to notice that she is "different."

Nevertheless, Isla's family has been very supportive and were excited to learn about her accomplishment.

"They have given her many learning gadgets and toys to aid her endeavours," said Jason.

"She has achieved quite a lot in her three years."

Jason says he was excited to see his daughter achieve a Guinness World Records title and is thrilled to see what opportunities present themselves to Isla.