An MIT statement regarding the research says:
Knowing the size and speed of the tongue, the researchers then developed a mathematical model involving the Froude number, a dimensionless number that characterises the ratio between gravity and inertia. For cats of all sizes, that number is almost exactly one, indicating a perfect balance.It seems that a normal cat - or a tiger, lion or jaguar - bends the tip of its tongue downward and then flicks it at the surface of its beverage of choice. The lingual piston thus formed is then whipped back into the mouth, causing a spout or column of liquid to surge up beneath it. The crafty feline allows this to fly into its mouth, so keeping its chin dry in fastidious style - as opposed to the slobbery methods of dogs, for instance.
The boffins discovered this by analysing high-speed videos of various sizes of cats drinking - including a lion, a tiger and a jaguar, thanks to cooperation from zookeepers. In order to test their theories they naturally had to construct a robotic cat-lapping lingual simulator, with gratifying results as we see here:
“As the project went on, we were surprised and amused by the beauty of the fluid mechanics involved in this system,” said Sunghwan Jung, an engineer whose research focuses on "soft bodies, such as fish, and the fluids surrounding them".
“The amount of liquid available for the cat to capture each time it closes its mouth depends on the size and speed of the tongue,” said Jeffrey Aristoff, a mathematician. “Our research — the experimental measurements and theoretical predictions — suggests that the cat chooses the speed in order to maximise the amount of liquid ingested per lap. This suggests that cats are smarter than many people think, at least when it comes to hydrodynamics.”
Grumbling taxpayers can rest easy, however.
"We did it without any funding, without any graduate students, without much of the usual apparatus that science is done with nowadays," insists biophysicist Roman Stocker. Apparently the scientists all "spent hours at the Stocker home", lurking with high-speed cameras poised around the bowl of Stocker's cat "Cutta Cutta". ("Cutta Cutta" is an Australian aboriginal name meaning "stars stars", apparently.)
“Science allows us to look at natural processes with a different eye and to understand how things work, even if that’s figuring out how my cat laps his breakfast,” Stocker says. “It’s a job, but also a passion, and this project for me was a high point in teamwork and creativity."