He has dyslexia, which makes it difficult for him to read and write.
He flunked out of university repeatedly.
But his dogged determination has seen him awarded two honorary doctorates.
Dr Jack Horner, 67, a US palaeontologist, has gone on to discover many dinosaurs, name 12 species and even inspired the main character in the Jurassic Park novel and movies.
The "dinosaur hunter" has become one of the most famous in the world, and is in Singapore to promote a travelling dinosaur exhibition which he curated.
In an interview with The New Paper on Wednesday, he said: "It's pretty incredible.
All I really wanted to do was to make even the smallest contribution to palaeontology."
Indeed, he has made several discoveries in over 35 years of working with dinosaurs.
In the 1970s, he discovered the first dinosaur eggs in North America, and was the first to prove that dinosaurs cared for their young.
The Museum of the Rockies in the US, where he is curator of palaeontology, also has the world's largest tyrannosaurus rex collection because of his fieldwork.
Two species of dinosaurs are even named after him - Achelosaurus Horneri and Anasazisaurus Horneri.
In the late 80s, novelist Michael Crichton modelled a fictional palaeontologist after Dr Horner.
This character was eventually portrayed by actor Sam Neill in Steven Spielberg's Jurassic Park franchise.
Dr Horner was the technical adviser for all three Jurassic Park movies and the cancelled American science-fiction TV series Terra Nova.
STRUGGLED IN SCHOOL
But as a child growing up in Montana, a state in the western US, Dr Horner struggled in school.
He said: "I was discouraged when I was very young - when my friends were all learning to read and I just couldn't do it.
"But I realised very early that there were lots of things I could do better than other kids, like coming up with new ideas and using my imagination, and finding fossils."
His dyslexia was diagnosed only in adulthood. But he has always been interested in dinosaurs.
He said: "I was born wanting to be a palaeontologist and have never really thought of being anything else."
At age eight, he discovered his first dinosaur remnant - the size of a fist - on a fossil-hunting trip. The bone is still in his office.
In the mid-1970s, he found a palaeontology position in a museum.
Looking back, he said: "Some people saw how passionate I was and realised that I did know more than my college records reflected.
"I always encourage dyslexic kids to not lose hope, and figure out what they can do better than non-dyslexics. "One is no better or no worse than the other. They simply use their brains differently."
The Science Centre Singapore has brought two international travelling dinosaur exhibitions from The Museum of the Rockies in the US and Aurea Exhibitions in Argentina to Singapore for the first time.
The 3,000 sq m exhibition opened on Friday at the centre.
It will include the largest T-Rex skull ever found - the first time it is on display here.
It will also showcase a 36m-long, 7m-tall skeleton cast of an argentinosaurus, among the largest known dinosaurs.
According to the Science Centre's website, there will also be animatronic mammals on show from the Ice Age, including a mammoth, a mastodon and a sabertoothed tiger.
WHAT: Titans of the Past - Dinosaurs and Ice Age Mammals
WHEN: Oct 25 to Feb 23, 2014, 10am to 6pm daily
WHERE: Science Centre Singapore, 15 Science Centre Road
ADMISSION: $25 for adults, $19 for children (inclusive of Science Centre entry)
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