The native parrots' intelligence is being put to the test by Victoria University PhD student Julia Loepelt.
Since January, the 28-year-old biologist from Germany has been giving the kaka a series of tasks to challenge them, with a tasty reward at the end.
"The tasks differ in what sort of cognitive abilities are needed to solve it, whether they have to memorise something or have to solve a novel problem," she said.
"You look at whether they are able to solve it, or how fast they solve it, or if they get faster."
The challenges include some Loepelt designed herself, such as "messing with" how they opened their sanctuary feeding station. Others had been tried on birds such as kea, including one that hung a treat on a string.
"The nut is out of reach, so they can't grab it from the tree, and it's too far from the ground to grab it from below. They have to understand that, if they pull the string up, they also pull the nut up."
Rather than experiencing difficulty in enticing the birds to undertake the various tasks, she found the problem was getting the 20 or so "regulars" to stop.
One bird in particular - nicknamed Amy, "as in Amy Farrah Fowler from The Big Bang Theory, because she's one of my brainiacs" - would undergo a task more than 20 times in a row to earn the nuts.
"As long as I keep attaching cashew nuts, they keep pulling the rope.
"I love it - I love watching the birds try to figure out the problems and the solutions."
Loepelt hopes to publish the first results of her experiments early next year.