But, a new study suggests that tool use is not related to cognitive ability. Using tools seems to be mentally demanding because it involves several skills, for example grabbing food with a stick involves learning the spatial relationship between two objects. Plus, a strong correlation has been found between tool use and brain size in birds and primates.
These studies don’t demonstrate that an animal is clever though. So Sabine Tebbich at the University of Vienna and colleagues compared the smarts of two species of Darwin’s finches: the woodpecker finch and its close relative, the small tree finch.
Both species live in the Galápagos archipelago, but small tree finches do not use tools, while woodpeckers can use twigs to poke arthropods out of tree holes. Tebbich also compared younger woodpecker finches that had not developed tool-use skills yet. Tebbich captured woodpecker and small tree finches and subjected them to four tasks, each testing different cognitive abilities.
First, food was balanced in the center of a seesaw, with a hole on one arm. The birds couldn’t get the food directly as it was covered by a plastic box. Instead they had to jump on a lever to let the food roll down so they could eat it. If the finches jumped on wrong lever, the tasty morsel would roll into the hole and be lost.
Five of the six small tree finches tested solved the task, while only two of the six tool-using woodpecker finches worked it out. None of the young woodpecker finches completed the task.
In a harder test, two canes were rested on a table with food placed within one. The bird had to pull one cane to get a reward, but they were connected with a string so pulling the wrong one caused the food to move out of reach. Successful birds spotted where location of the food, and knew to pull the cane that brought the food close to them. Eight of 12 woodpecker finches – three non tool-users and five tool users – and all six small tree finches successfully completed the task.
Testing the bird’s ability to unlearn, the animals were next shown two lids of different colours – orange and blue – with food always hidden under the same coloured lid. Once the birds knew where the food was, the researchers reversed the lids. Again, the small tree finches outperformed the woodpeckers by learning the new rule faster.
The only test where the tool using woodpeckers surpassed small tree finches was a box-opening task. Woodpeckers opened a box with an opaque lid using their beaks, while small tree finches hopelessly pecked the top of box to get the goodies inside.
“Everybody, for god knows how long, has been making a blind assumption that if you use a tool you are intelligent,” says Calum Brown an ecologist at Macquarie University in Sydney, who was not involved in the work. “It’s such an overwhelming idea in this field, but this shows it’s not the case.”
Alex Kacelnik a behavioural ecologist at Oxford University, UK agrees. “While it is valid to use flimsy arguments and intuition to form a hypothesis, it takes systematic reasoning and experimentation to prove it. Tebbich has been a pioneer.”
According to Brown, some animals maybe use tools through trial and error, which doesn’t mean they’re smart. “You need to really show that there is some kind of higher order cognitive process going on,” says Brown. For example an animal might be aware that if they push something, another action will happen. One way to prove this, says Brown, would be to show animals a task and give them one chance to solve it.
Russell Gray at the University of Auckland, New Zealand points out that making tools is a lot more cognitively demanding than using them. So, there are still good reasons for thinking animals making tools makes us smart.
Journal Reference: Animal Behaviour doi:10.1016/j.anbehav.2011.07.032
Image credit: Erica Cartmill