Little did he know then that his love of dinosaurs would lead to a career as a paleontologist. Since the day his father brought home a special gift for him -- a toy dinosaur set -- after a business trip, Kirkland has spent nearly 50 years traveling the world unearthing fossils.
"Every time I find something new, it's just as exciting as the first time," said Kirkland, state paleontologist of Utah with the Utah Geological Survey.
Many children develop a love of dinosaurs at an early age, but most of the time, they don't become world-renowned paleontologists. Instead, it wanes, said Dr. Arthur Lavin, chair of the American Academy of Pediatrics committee on the Psychosocial Aspects of Child and Family Health.
Kids ages 3 to 4 go through a period of hyperfixation, which Lavin called "imagination-based play," where they become deeply interested in subjects like fairies, monsters, or in some cases, dinosaurs.
When babies are born, they aren't aware they exist for the first three months, he said. For the first year, there's no clearly defined sense of "self," Lavin noted.
At around 18 months old to 3 years old, children begin developing their sense of self but are still confused about the world around them, he said.
"It's why we call them the terrible twos because they know things aren't the way they want them, but they're not sure how they want them," or how to get them the way they want, Lavin said.
At age 3, they begin to master this sense that they're in the world, and they want to try out ideas, he said.
Children then embark on this journey of creating this thing called "self," and one of the ways they do that is to make up stuff in the world they've created, Lavin explained.
Dinosaurs fit into an imaginary play
Dinosaurs fit into their make-believe world because there aren't any alive today, so they're sort of like unicorns and fairies, he said.
"If you're going to have a make-believe world, which fits into this very powerful sense of developing a sense of self, dinosaurs really fit the bill," Lavin said.
Some children with a keen interest in the extinct animals can recite complicated dinosaur names and facts from memory, which was a pastime for Kirkland.