difference between large and small collections of things. One celebrated parrot is credited with the recognition of “zero”, or nothing, as a separate quantity, but numeracy in insects has not been widely studied.
There is evidence that animals and birds can count up to small numbers and make out the
Scarlett R Howard, Aurore Avargues-Weber, Jair E Garcia, Andrew D Greentree and Adrian G Dyer, from the National Centre for Nuclear Science, Toulouse and the Royal Melbourne Institute of Technology and Monash Universities, Australia, report in the journal Science a trial where honey bees could tell apart different numbers of objects shown including “no objects”.
Understanding the concept of zero has been regarded as an important intellectual advance of humans and generally unique to us, the paper says. Although there is evidence that some animals have a grasp of “nothing” as being distinct, finding this ability in the distantly related species of the honey bee suggests that it is a widespread evolutionary response to the complexity of surroundings, the paper says.
A legendary story is about farmers who tested how far crows could count. A farmer walks up to a cornfield where crows are feeding, fires a gunshot in the air and goes into a cabin in the middle of the field. The crows scatter and do not return till they see the farmer walking out. The next time round, after the farmer fires the shot and enters the cabin, another farmer does the same.
A little later, one of the farmers leaves, but the crows do not return, they wait till the second farmer has gone. It works the same way with three farmers and four farmers. But when there are five, the crows get uncertain when the fourth farmer left. Crows can hence count up to four, but the number five seems to be out of their reach.
Number sense has been observed in many animals – primates, dogs, birds, rats, even fish. A prominent example is of Otto Koehler’s work with a raven, Jacob, who was able to make out the numbers in collections of up to five objects. Another well known study is by Francis and Platt and Johnson, where rats learnt to press a lever between four and 16 times, as specified by the researchers, to obtain food. Work with primates has shown the ability of animals to do simple addition and even to work with fractions.
A more recent study is by Pepperberg and Gordon of Brandeis University, where a grey parrot called Alex was able to differentiate numbers of different objects, up to six, and then articulate the number, or point to a lot with a particular number of objects when the number was spoken. He knew the numbers from one to six and could say how many green blocks there were in a mixed lot of blue, red and green, even when there were both blocks and balls of different colours.
The question could then be switched, asking Alex to identify the group with four balls, for instance, from a collection of groups with different numbers. While Alex could tell the correct number 80 per cent of the time, he even responded with “none” when the answer was the absence of quantity.
“Alex demonstrated numerical comprehension competence comparable to that of chimpanzees and very young children,” Pepperberg and Gordon say. This last aspect, of recognising “nothing” as a number, is of special interest. It is fairly recently, compared to the development of language and numeracy, that the concept of zero has appeared in human civilisation.
The first symbol to denote zero was used by the Babylonians in 300 BCE. The Babylonians used a number system based on a base of 60, as opposed to our own decimal system, based on the number, 10 and had complex mathematical ability.
While they had a symbol for zero, they did not make full use of it – the symbol could appear within the number, to indicate the absence of quantity, like we may have in “204”, but not at the end of a number, like “350” in our system.
It was only over the following millennium that the use of zero was developed, by mathematicians, Pingala to Aryabhatta, in India. That it was only in an advanced stage of civilisation that zero appeared in human computation makes it all the more remarkable that the concept exists in the animal world.
The work of the CNRS and Australian researchers is with the counting ability of the honey bee. The experimental set-up comprised a pair of panels, which displayed some numbers of dots. As bees were known to be able to count up to five, the panels had one to five dots, and each panel had a different number of dots.
The game was for the bees to identify which panel had fewer dots. If they got it right, they were rewarded with sweetened water. If they got it wrong, they got a bitter quinine solution.
The bees soon learnt the idea of “greater than” and “less than”, and managed to get sweetened water most of the time. When the bees were trained, they were presented with a pair of panels where one was blank and the other had one or more dots. This time, the bees chose the blank panel – which indicates that they considered “no dots” to be less than one or more dots. This suggests that they identified “no dots” as signifying “zero” and assigned the number a lower value than the others.
A press release from CNRS notes that the bee brain has only a million neurons, which is a hundred thousand times less than what we have. The concept of zero is a pretty abstract one, which may be the reason that humans took many centuries to come to grips with it.
Numbers themselves are understood as abstraction of the property that is shared by equal numbers of different objects. Zero would then be the number of objects when there are none, which is a degree of abstraction above that of other numbers.
When the bee sees “no dots” in the panel, what the brain receives is “no stimulus”, as opposed to the stimuli from the dots. The brain often registers “no stimulus” when the eye sees a blank slate. But to translate this as “zero dots” in the context of counting is an act of some sophistication.
That the rudimentary brain of the honey bee should invest its resources in having this ability suggests that the concept of zero has another level where it plays a role in the survival of species.