They may only have a brain the size of a thimble, but it appears pigeons can categorise and name objects in the same way a human children learn new words.
A new study from the University of Iowa has shown that the birds are capable of learning to categorise 128 different photographs into 16 basic categories.
Scientists taught three pigeons to attribute different breeds of dog or types of shoe, for example to a particular symbol in exchange for a reward.
CROWS ARE PROBLEM SOLVERS
Crows are widely thought to be among the most intelligent of birds, but a recent study found they are even smarter than first thought, capable of solving complex tasks previously thought possible only by humans, apes and monkeys.
Most impressively, they performed the tasks spontaneously – without any prior training.
Two hooded crows were placed into a wire mesh cage into which a plastic tray containing three small cups was occasionally inserted.
The sample cup in the middle was covered with a small card that had a colour, shape or number of items pictured on it.
The other two cups were also covered with cards – one that matched the sample, and one that didn’t.
The cup under the matching card contained mealworms, which the crows were rewarded with if they chose the correct match.
The crows were then required to conduct a similar task but with images on cards that did not precisely match.
Researchers were surprised that the not only could the crows correctly perform these relational matches, with a success rate of 78 per cent – 50 per cent being regarded as chance – but that they did so spontaneously, without explicit training.
However, the researchers said it took their birds around 40 days to perfect the task of learning just 16 categories.
Professor Edward Wasserman, a psychologist at the University of Iowa who led the work, said: ‘Our birds’ rate of learning appears to have been quite slow. Human adults regularly learn 16 categories in the space of an hour, yet, pigeons took 45,000 trials to reach their associative limits.
‘Would children learn faster than pigeons? Almost certainly. However, our pigeons came to the experiment with literally no background knowledge.
‘They did not understand the nature of the “task”, they had not encountered these categories before, and they had empty lexicons.
‘Children, on the other hand, bring all of these things to bear on the problem of learning words.
‘Thus, the more relevant comparison group may be newborn infants, who indeed take 6–9 months to learn their first words.’
On each training day, the researchers presented each of the pigeons with 128 randomly ordered images.
Each image fitted into one of 16 categories – baby, bottle, cake, car, cracker, dog, duck, fish, flower, hat, key, pen, phone, plan, shoe, tree.
The birds then had to peck on one of two different colour symbols presented to them on a touchscreen computer – one that was associated with the correct category and the other the wrong category.
If the birds selected the correct symbol they were rewarded with a pellet of food. Incorrect choices plunged the birds into darkness foir a new seconds.
After the training, the birds were then presented with images from the categories they had not seen before to see if they could correctly attribute them.
Pigeons are known for their ability to find their way home, but the new study suggests they are even smarter
One of the birds reached an accuracy of 80 per cent, a second achieved 70 per cent accuracy and the third was 65 per cent accurate.
Writing in the journal Cognition, the researchers said their experiment was a very simple mirror of the way children are taught words – by their parents pointing to pictures and asking them to name the object.
They said: ‘Our paradigm is not a direct analog of human word learning.
‘Nevertheless, it does offer a unique biological model of a critical property of word learning – namely, the fact that a learner must map many exemplars to many categories.’
Professor Wasserman added: ‘Unlike prior attempts to teach words to primates, dogs, and parrots, we used neither elaborate shaping methods nor social cues.
‘Our pigeons were trained on all 16 categories simultaneously, a much closer analog of how children learn words and categories.
‘Differences between humans and animals must indeed exist – many are already known – but, they may be outnumbered by similarities.
‘Our research on categorization in pigeons suggests that those similarities may even extend to how children learn words.’
The scientists taught the pigeons to group images of real objects into the 16 distinct categories shown above
Pigeons are known to be smarter than many birds and their homing instinct allows them to memorise their location and find their way home from hundreds of miles away.
Professor Bob McMurray, another psychologist who took part in the study, said the results showed that human learning is not as unique as was previously believed.
He said: ‘Children are confronted with an immense task of learning thousands of words without a lot of background knowledge to go on.
‘For a long time, people thought that such learning is special to humans.
‘What this research shows is that the mechanisms by which children solve this huge problem may be mechanisms that are shared with many species.’
CROWS ARE ‘LEFT-BEAKED’ OR ‘RIGHT-BEAKED’
Researchers studying New Caledonian crows recently discovered the clever corvids display a preference for holding a stick tool on a certain side of their beaks – and this could be to make the most of their wide field of vision.
The researchers believe the birds may be trying to keep the tip of the stick in view of the eye on the opposite side of their heads, so they can see clearly in order to use tools in the most dexterous way.
Lead scientist Dr Alejandro Kacelnik, from Oxford University, said: ‘If you were holding a brush in your mouth and one of your eyes was better than the other at brush length, you would hold the brush so that its tip fell in view of the better eye. This is what the crows do.’
New Caledonian crows surprised experts with their ability to use sticks to extract larvae from burrows and, in captivity, retrieve food placed out of reach.
The study, published in the journal Current Biology, also suggests that the birds’ unusually wide field of vision actually helps them to see better with one eye.
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