By Paul Rincon
BBC News science reporter, St Louis
Tyrannosaurus rex may have been a big beast, but it appears to have possessed the sensory skills of much smaller, more agile animals.
Scavenger or top predator?
The finding is something of a puzzle in light of other evidence showing it had only a limited range of movement.
Palaeontologists presented their latest research on the carnivorous dinosaur at a conference in St Louis, US.
The results inform the hot debate over T. rex's feeding behaviour: was it more scavenger than top predator?
Dr Lawrence Witmer, from Ohio University, used the medical scanning technique of computed tomography (CT scanning) to reconstruct the shape of the animal's brain, including its inner ear, which is involved not only in hearing but also balance.
The structure of its inner ear suggests it had excellent hearing and balance.
"The inner ear provides very important clues about behaviour," said Dr Witmer. "It talks of relative types of movement; for example, how agile they were.
"T. rex has the inner ear of a much smaller, very agile animal. It had a heightened sense of equilibrium and balance.
"But there's evidence it went beyond that, that it emphasised that."
The Ohio researcher said the T. rex also employed rapid turning movements of its eyes and head to track its prey.
However, Dr Jack Horner, a leading expert on Tyrannosaurus rex, has uncovered evidence that casts the dinosaur as lumbering and awkward.
The animal possessed a strong ligament that would have made its body very rigid, restricting its range of movement, he said.
"It was rigid from the neck all the way back to the tail," Dr Horner told the BBC News website. "It wasn't a dancer."
Dr Horner and colleagues carried out microscopic analysis of the dinosaur's vertebrae. They found tissue remnants related to the animal's nuchal ligament, which provides passive support for the head and neck.
Since the amount found in the vertebrae is proportional to how stiff the ligament would have been, the researchers determined it would have been very rigid in their T. rex.
"We think this applied to all dinosaurs, certainly all saurischians - all the meat-eating dinosaurs and all the sauropods," Dr Horner said.
"I think we need to re-model dinosaurs and think of them as being very rigid. They're just not as fluid as we thought."
They would have needed lots of space to turn in order to avoid falling over, he added.
Despite evidence of rapid eye movement to track prey, Horner thinks the overall evidence points to T. rex being a scavenger rather than a top predator.
The dinosaur has been found in comparatively large numbers - top predators tend to be comparatively rare - and also had teeth specialised for crushing bone.
"You don't need bone-crushing teeth if you're killing another animal, you just take the meat and go," he explained.
Dr Horner and Dr Witmer presented their evidence at the annual meeting of the American Association for the Advancement of Science (AAAS).