Corvus crows research paper

"Cognitive Processes Associated with Sequential Tool Use in New Caledonian Crows"

by

Joanna H. Wimpenny, Alex A. S. Weir, Lisa Clayton, Christian Rutz, Alex Kacelnik

Abstract:

Using tools to act on non-food objects—for example, to make other tools—is considered to be a hallmark of human intelligence, and may have been a crucial step in our evolution. One form of this behaviour, ‘sequential tool use’, has been observed in a number of non-human primates and even in one bird, the New Caledonian crow (Corvus moneduloides). While sequential tool use has often been interpreted as evidence for advanced cognitive abilities, such as planning and analogical reasoning, the behaviour itself can be underpinned by a range of different cognitive mechanisms, which have never been explicitly examined. Here, we present experiments that not only demonstrate new tool-using capabilities in New Caledonian crows, but allow examination of the extent to which crows understand the physical interactions involved.
Methodology/Principal Findings

In two experiments, we tested seven captive New Caledonian crows in six tasks requiring the use of up to three different tools in a sequence to retrieve food. Our study incorporated several novel features: (i) we tested crows on a three-tool problem (subjects were required to use a tool to retrieve a second tool, then use the second tool to retrieve a third one, and finally use the third one to reach for food); (ii) we presented tasks of different complexity in random rather than progressive order; (iii) we included a number of control conditions to test whether tool retrieval was goal-directed; and (iv) we manipulated the subjects' pre-testing experience. Five subjects successfully used tools in a sequence (four from their first trial), and four subjects repeatedly solved the three-tool condition. Sequential tool use did not require, but was enhanced by, pre-training on each element in the sequence (‘chaining’), an explanation that could not be ruled out in earlier studies. By analyzing tool choice, tool swapping and improvement over time, we show that successful subjects did not use a random probing strategy. However, we find no firm evidence to support previous claims that sequential tool use demonstrates analogical reasoning or human-like planning.
Conclusions/Significance

While the ability of subjects to use three tools in sequence reveals a competence beyond that observed in any other species, our study also emphasises the importance of parsimony in comparative cognitive science: seemingly intelligent behaviour can be achieved without the involvement of high-level mental faculties, and detailed analyses are necessary before accepting claims for complex cognitive abilities.

Entire paper


An Aesop fable and learning

An Aesop fable and learning

"The Crow and the Pitcher"

by

Æsop

In a spell of dry weather, when the Birds could find very little to drink, a thirsty Crow found a pitcher with a little water in it. But the pitcher was high and had a narrow neck, and no matter how he tried, the Crow could not reach the water. The poor thing felt as if he must die of thirst.

Then an idea came to him. Picking up some small pebbles, he dropped them into the pitcher one by one. With each pebble the water rose a little higher until at last it was near enough so he could drink.

In a pinch a good use of our wits may help us out.

The following is from Wired and certainly illustrates some form of "reasoning". I remember a similar instance where a crow had a black walnut [whose shell is extremely hard and easily breached by a squirrel's incisors] and figured that the delicious nut meat could be removed and enjoyed by placing the black walnut in traffic and letting the vehicles crack the hard shell.

"Clever Crows Prove Aesop's Fable Is More Than Fiction"

by

Hadley Leggett

August 6th, 2009

Wired

Aesop's fables are full of talking frogs and mice who wear clothes, but it turns out at least one of the classic tales is scientifically accurate.

Researchers presented four crows with a challenge from Aesop's fable "The Crow and the Pitcher": a container of water not quite full enough for the birds to reach with their beaks. Just like Aesop's crow, all four birds figured out how to raise the water level by dropping stones into the glass. The crows also selectively chose large pebbles over small ones, and quickly realized that dropping rocks into a container of sawdust didn't have the same effect.

"The results of these experiments provide the first empirical evidence that a species of corvid is capable of the remarkable problem-solving ability described more than two thousand years ago by Aesop," wrote the researchers in the paper published Thursday in Current Biology. "What was once thought to be a fictional account of the solution by a bird appears to have been based on a cognitive reality."

The researchers took four adult rooks, a type of intelligent crow, and tempted them with a tasty worm floating on top of a glass of water, just out of reach. Then they placed a pile of small rocks next to the crows. After they assessed the height of the water from the top and sides of the glass, the crows dropped stones into the glass until the water level rose enough for them to grab their prize.

Once they'd caught the worm, the birds didn't keep putting stones in the glass, and they didn't try to grab the worm until they'd dropped in a certain number of stones. "This number was strongly correlated to the number of stones needed to raise the water level to the correct height," the researchers wrote, "suggesting that, having assessed the starting level of the water, rooks translated this into an estimate of the number of stones needed."

Before this experiment, the birds had never been exposed to a glass with water in it, and they'd never used stones as tools. According to the researchers, the only other animal known to perform this kind of task is the orangutan, which has been recorded spitting into a tube to bring a peanut into reach.

"Corvids are remarkably intelligent, and in many ways rival the great apes in their physical intelligence and ability to solve problems," said biologist Christopher Bird of the University of Cambridge in a press release. "This is remarkable considering their brain is so different to the great apes'."

The antics of the four birds - Cook, Fry, Connelly and Monroe - can be seen in the videos below. Cook and Fry snagged the floating worm after just one try, while Connelly and Monroe succeeded after two attempts. Unfortunately, Fry had a bad reaction to one of the worms and gave up in the middle of the experiment.

Was the rook aware of the fundamentals of Archimedes' principle: "Any object, wholly or partly immersed in a fluid, is buoyed up by a force equal to the weight of the fluid displaced by the object."

Drop an "x" quantity of pebbles into the water filled cylinder and retrieve the food.

Now note that the rook employs an extended cognitive feature...not just any stone--size does matter.

Change the medium [sand for water] and the rook quickly discovers the medium that will yield the food.