Can animals count?
Can animals count?
Brannon. Humans can do this with ease – providing the ratio is big enough – but do other animals
share this ability? In one experiment, rhesus monkeys and university students examined two sets of
geometrical objects that appeared briefly on a computer monitor. They had to decide which set
contained more objects. Both groups performed successfully but, importantly, Brannon’s team found
that monkeys, like humans. make more errors when two sets of objects are close in number. The
students’ performance ends up looking just like a monkey’s. It’s practically identical.’ she says.
Humans and monkeys are mammals, in the animal family known as primates. These are not the only
animals whose numerical capacities rely on ratio, however. The same seems to apply to some
amphibians. Psychologist Claudia Uller’s team tempted salamanders with two sets of fruit flies held in
clear tubes. In a series of trials, the researchers noted which tube the salamanders scampered towards,
reasoning that if they could recognize the number, they would head for the larger number. The
salamanders successfully discriminated between tubes containing 8 and 16 flies respectively, but not
between 3 and 4. 4 and 6, or 8 and 12. So it seems that for the salamanders to discriminate between
two numbers, the larger must be at least twice as big as the smaller. However, they could differentiate
between 2 and 3 flies just as well as between 1 and 2 flies, suggesting they recognize small numbers
differently from larger numbers.
Further support for this theory comes from studies of mosquitofish, which instinctively join the
biggest shoal* they can. A team at the University of Padova found that while mosquito fish can tell the
difference between a group containing 3 shoal-mates and a group containing 4, they did not snow a
preference between groups of 4 and 5. The team also found that mosquitofish can discriminate between
numbers up to 16, but only if the ratio between the fish in each shoal was greater than 2:1. This
indicates that the fish, like salamanders, possess both the approximate and precise number systems
found in more intelligent animals such as infant humans and other primates.
While these findings are highly suggestive, some critics argue that the animals might be relying on
other factors to complete the tasks, without considering the number itself. ‘Any study that’s claiming an
animal is capable of representing number should also be controlling for other factors,’ says Brannon.
Experiments have confirmed that primates can indeed perform numerical feats without extra clues, but
what about the more primitive animals? To consider this possibility, the mosquitofish tests were
repeated, this time using varying geometrical shapes in place of fish. The team arranged these shapes so
that they had the same overall surface area and luminance even though they contained a different
number of objects. Across hundreds of trials on 14 different fish, the team found they consistently
discriminated 2 objects from 3. The team is now testing whether mosquito fish can also distinguish 3
geometric objects from 4.
Even more primitive organisms may share this ability. Entomologist Jurgen Tautz sent a group of bees
down a corridor, at the end of which lay two chambers – one which contained sugar water, which they
like, while the other was empty. To test the bees’ numeracy, the team marked each chamber with a
different number of geometrical shapes – between 2 and 6. The bees quickly learned to match the
number of shapes with the correct chamber. Like the salamanders and fish, there was a limit to the
bees’ mathematical prowess – they could differentiate up to 4 shapes, but failed with 5 or 6 shapes.
These studies still do not show whether animals learn to count through training, or whether they are
born with the skills already intact. If the latter is true, it would suggest there was a strong evolutionary
advantage to a mathematical mind. Proof that this may be the case has emerged from an experiment
testing the mathematical ability of three- and four-day-old chicks. Like mosquitofish, chicks prefer to be
around as many of their siblings as possible, so they will always head towards a larger number of their
kin. It chicks spend their first few days surrounded by certain objects, they become attached to these
objects as if they were family. Researchers placed each chick in the middle of a platform and showed it
two groups of balls of paper. Next, they hid the two piles behind screens, changed the quantities and
revealed them to the chick. This forced the chick to perform simple computations to decide which side
now contained the biggest number of its “brothers”. Without any prior coaching, the chicks scuttled to
the larger quantity at a rate well above chance. They were doing some very simple arithmetic, claim tho
researchers.
Why these skills evolved is not hard to imagine since it would help almost any animal forage for food.
Animals on the prowl for sustenance must constantly decide which tree has the most fruit, or which
patch of flowers will contain the most nectar. They are also other, less obvious, advantages of
numeracy. In one compelling example, researchers in America found that female coots appear to
calculate how many eggs they have laid – and add any in the nest laid by an intruder – before making
any decisions about adding to them. Exactly how ancient these skills are is difficult to determine,
however. Only’ by studying the numerical abilities of more and more creatures using standardized
procedures can we hope to understand the basic preconditions for the evolution of number.
share this ability? In one experiment, rhesus monkeys and university students examined two sets of
geometrical objects that appeared briefly on a computer monitor. They had to decide which set
contained more objects. Both groups performed successfully but, importantly, Brannon’s team found
that monkeys, like humans. make more errors when two sets of objects are close in number. The
students’ performance ends up looking just like a monkey’s. It’s practically identical.’ she says.
Humans and monkeys are mammals, in the animal family known as primates. These are not the only
animals whose numerical capacities rely on ratio, however. The same seems to apply to some
amphibians. Psychologist Claudia Uller’s team tempted salamanders with two sets of fruit flies held in
clear tubes. In a series of trials, the researchers noted which tube the salamanders scampered towards,
reasoning that if they could recognize the number, they would head for the larger number. The
salamanders successfully discriminated between tubes containing 8 and 16 flies respectively, but not
between 3 and 4. 4 and 6, or 8 and 12. So it seems that for the salamanders to discriminate between
two numbers, the larger must be at least twice as big as the smaller. However, they could differentiate
between 2 and 3 flies just as well as between 1 and 2 flies, suggesting they recognize small numbers
differently from larger numbers.
Further support for this theory comes from studies of mosquitofish, which instinctively join the
biggest shoal* they can. A team at the University of Padova found that while mosquito fish can tell the
difference between a group containing 3 shoal-mates and a group containing 4, they did not snow a
preference between groups of 4 and 5. The team also found that mosquitofish can discriminate between
numbers up to 16, but only if the ratio between the fish in each shoal was greater than 2:1. This
indicates that the fish, like salamanders, possess both the approximate and precise number systems
found in more intelligent animals such as infant humans and other primates.
While these findings are highly suggestive, some critics argue that the animals might be relying on
other factors to complete the tasks, without considering the number itself. ‘Any study that’s claiming an
animal is capable of representing number should also be controlling for other factors,’ says Brannon.
Experiments have confirmed that primates can indeed perform numerical feats without extra clues, but
what about the more primitive animals? To consider this possibility, the mosquitofish tests were
repeated, this time using varying geometrical shapes in place of fish. The team arranged these shapes so
that they had the same overall surface area and luminance even though they contained a different
number of objects. Across hundreds of trials on 14 different fish, the team found they consistently
discriminated 2 objects from 3. The team is now testing whether mosquito fish can also distinguish 3
geometric objects from 4.
Even more primitive organisms may share this ability. Entomologist Jurgen Tautz sent a group of bees
down a corridor, at the end of which lay two chambers – one which contained sugar water, which they
like, while the other was empty. To test the bees’ numeracy, the team marked each chamber with a
different number of geometrical shapes – between 2 and 6. The bees quickly learned to match the
number of shapes with the correct chamber. Like the salamanders and fish, there was a limit to the
bees’ mathematical prowess – they could differentiate up to 4 shapes, but failed with 5 or 6 shapes.
These studies still do not show whether animals learn to count through training, or whether they are
born with the skills already intact. If the latter is true, it would suggest there was a strong evolutionary
advantage to a mathematical mind. Proof that this may be the case has emerged from an experiment
testing the mathematical ability of three- and four-day-old chicks. Like mosquitofish, chicks prefer to be
around as many of their siblings as possible, so they will always head towards a larger number of their
kin. It chicks spend their first few days surrounded by certain objects, they become attached to these
objects as if they were family. Researchers placed each chick in the middle of a platform and showed it
two groups of balls of paper. Next, they hid the two piles behind screens, changed the quantities and
revealed them to the chick. This forced the chick to perform simple computations to decide which side
now contained the biggest number of its “brothers”. Without any prior coaching, the chicks scuttled to
the larger quantity at a rate well above chance. They were doing some very simple arithmetic, claim tho
researchers.
Why these skills evolved is not hard to imagine since it would help almost any animal forage for food.
Animals on the prowl for sustenance must constantly decide which tree has the most fruit, or which
patch of flowers will contain the most nectar. They are also other, less obvious, advantages of
numeracy. In one compelling example, researchers in America found that female coots appear to
calculate how many eggs they have laid – and add any in the nest laid by an intruder – before making
any decisions about adding to them. Exactly how ancient these skills are is difficult to determine,
however. Only’ by studying the numerical abilities of more and more creatures using standardized
procedures can we hope to understand the basic preconditions for the evolution of number.
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