I’ve never read the actual book before now but for the most part and certainly based on the contents of the book thus far it is very clear the man had a knack for scientific depth. He reminds me a lot of Andy Weir.

This made it odd that when I reached the iconic scene where the T. rex escapes it turns out that the not moving trope was featured in the book; I frankly expected it to be a Hollywood only move. Given the incredible scientific depth of the rest of the book this sticks out as something very not scientific.

Does anyone know why he included it? Granted, it wasn’t until after the book was written that more in depth studies were done on the vision of dinosaurs but even at the time it was clear that the T. rex had forward facing, binocular, vision and there was no scientific basis for saying a T. rex wouldn’t see a still person (the fact that even if it couldn’t see one - it would certainly smell one aside).

Had it been another book by another author it wouldn’t have registered but the fact that it’s Michael Crichton makes it weird to me.


3 Answers 3


In the novel Jurassic Park, Michael Crichton makes the point that frog DNA was used to fill gaps in the genetic code where genuine dino DNA was missing. As an unintended consequence, the dinosaurs proved able to change sex under some circumstances, as happens with some living frogs. Crichton evidently also remembered that some frogs have difficulty in noticing motionless prey, and incorporated that into the vision of his Tyrannosaurus rex.

As pointed out in comments by Hypnosifl and FuzzyBoots, book paleontologist Grant warns the others of the limitations of T. rex vision only after the dinosaur lost track of him when he froze, and the park's veterinarian (who, unlike Grant, would be aware of the frog DNA), says, "Dinosaurs have excellent visual acuity, but they have a basic amphibian visual system: it's attuned to movement. They don't see unmoving things well at all."

As it turns out, in real life T. rex had great binocular vision and probably would have had no trouble discerning immobile prey. Bob Bakker mentioned its stereoscopic vision in The Dinosaur Heresies (1986, p. 270). Crichton probably read that book, as it also established that dinosaurs moved much more rapidly than had long been supposed, and Jurassic Park is all about active dinosaurs. Bakker said nothing about the invisibility of immobile prey, so this must be an embellishment by Michael Crichton.

  • 5
    Also worth noting that the novel has Grant freeze and then notice that the dinosaur seemed to have lost track of him, not that he necessarily knew in advance that it would happen.
    – FuzzyBoots
    Dec 9, 2021 at 3:57
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    Yes, in the movie Grant somehow already knew T. rex's vision was "based on movement", but in the book Grant just froze with fear and then noticed the T. rex went right past him, and he asked himself "Was it possible the tyrannosaur hadn't seen him? It seemed as if it hadn't. But how could that be?". Later the park's vet, Gerry Harding, explained that "Dinosaurs have excellent visual acuity, but they have a basic amphibian visual system: it's attuned to movement. They don't see unmoving things well at all."
    – Hypnosifl
    Dec 9, 2021 at 4:21
  • Thank you both. I have incorporated your comments into the answer, which is much improved thereby... Dec 9, 2021 at 18:20
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    If I recall correctly, the sequel book The Lost World has a scene tearing apart Grant's conjecture from the Jurassic Park book. Namely, the T-Rex had just eaten, and decided it was more interested in escaping from its enclosure than eating Grant too.
    – notovny
    Dec 10, 2021 at 0:41
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    Saying that amphibian vision is motion-based is an over-simplification. All vision systems are good at detecting motion, and some motion detection occurs in the retina itself, see en.wikipedia.org/wiki/Feature_detection_(nervous_system) Toads don't have saccadic vision, but they efficiently compensate for that, see en.wikipedia.org/wiki/Vision_in_toads
    – PM 2Ring
    Oct 1, 2022 at 6:17

Just adding to Invisible Trihedron's answer, several dinosaurs have issue with viewing people who are standing still, behind water, in the dark, etc, implying that there's a general visual field issue caused by the revival process.

"Forget it," Lex said. "I'm not staying here." She started to climb down the branches. At her movement, the hadrosaur trumpeted in fresh alarm.

Grant was amazed. He thought, It really can't see us when we don't move. And after a minute it literally forgets that we're here. This was just like the tyrannosaur-another classic example of an amphibian visual cortex. Studies of frogs had shown that amphibians only saw moving things, like insects. If something didn't move, they literally didn't see it. The same thing seemed to be true of dinosaurs.


The head came through the water again, but slowly this time, and the jaw came to rest on the ground. The tyrannosaur snorted, flaring its nostrils, breathing the air. But the eyes were still outside the sheet of water.

Tim thought: He can't see us. He knows we're in here, but he can't see through the water.


Slowly, Tim lowered his body, sinking beneath the table. . . . The velociraptor jerked its head around, looking directly at Tim. Tim froze. He was still exposed, but he thought, Don't move.
The velociraptor stood motionless in the doorway.
It's darker here, Tim thought. He can't see so well. It's making him cautious.


Since no T-Rexes are alive to confirm their vision capability, Michael has quite appropriately employed poetic license to write that which he felt best fit his fictional storyline.

  • thanx for the syntax heads up lfurini....i've gotten sloppy from years of FB texting. i do like the formality imposed by this site.
    – ziggypiggy
    Dec 29, 2022 at 1:38

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