http://news.independent.co.uk/world/science_technology/story.jsp?story=611403
This little piggy has depression
Scientists now say they can tell a happy animal from a
sad one. But should this discovery inform the way we
look after them? Sanjida O'Connell reports
16 February 2005
Should we be using IQ as a benchmark for how we treat
what we eat? Dr Michael Mendl, from Bristol
University, has been studying pigs for 16 years and
conducted a research project on the animals with Dr
Suzanne Held, also from Bristol, and Professor Richard
Byrne, from St Andrews. Mendl and Herne were mimicking
experiments that had been performed on apes, which
showed how similar primate intelligence is to human
intelligence. Mendl was interested to see if studies
such as these, showing just how smart apes, dolphins
and monkeys were, would also show that farm animals
were not intelligent. And, if so, could such findings
justify our treatment of livestock?
Traditionally, scientists searching for insight into
animal intelligence have tended to equate a high IQ
with a level of consciousness analogous to our own.
But Professor Marian Dawkins, an animal behaviourist
at Oxford University, argues that there is a "pitfall"
in linking consciousness to intelligence. Mendl
agrees. "There is an implicit assumption that the more
clever an animal is, the more likely it is to suffer,
and I'm not sure that there is a clear link between
the two," he says. An accurate assessment of how
animals feel, as well as how they think, is vital to
ensure a high standard of animal welfare, he says.
There have been a number of sophisticated studies
designed to assess consciousness and cognition. In one
American experiment, humans and animals had to observe
a box on a dark computer screen containing a variable
number of illuminated pixels. The subjects had to
indicate whether that box contained a high density of
pixels (more than 2950) or a sparsity (up to 2949),
which became harder in the middle range, moving, say,
between 2950 and 2949. The subjects could also
indicate that they were uncertain.
Humans, monkeys and dolphins were able to perform this
task, the humans and monkeys using buttons or levers
and the dolphins using paddles. And the ability to
indicate that they didn't know the answer, in response
to the harder tests, showed that members of all three
species had a degree of mental awareness. Scientists
sometimes equate this kind of intelligence with
self-awareness - a high degree of consciousness. Rats
and pigeons, however, were unable to use the
"uncertain" key, which may mean that they are not
conscious of their thoughts.
However, an animal that is not aware of its thoughts
may still be aware of its feelings and emotions. An
awareness of sensations and emotions is known as
"feelings consciousness". As far as welfare is
concerned, this is the crux of the matter: what an
animal feels, not just what it thinks.
"Animals like us that are clever are more likely to
suffer because they can think about suffering in the
future and remember suffering in the past. But they
are also capable of understanding that pain is going
to stop. Less intelligent animals may not have this
capacity," says Mendl. They may, therefore, be worse
off because they suffer not knowing their pain can
end.
How can we tell what an animal feels? We may never
know for certain because feelings, even those of our
nearest and dearest, are often private experiences.
However, experiments based on what is known about
human emotions help. Mendl and Drs Emma Harding and
Elizabeth Paul, also from Bristol University, have
devised a test based on assessing human "feelings
consciousness" and made it applicable to rats. "What
we're doing is looking at humans as a model for
animals," says Paul. The team are interested in
determining whether rats react like people when they
are depressed. "Depressed, anxious people judge
ambiguous events negatively - this is a very clear and
robust finding in clinical psychology," says Paul.
First, the researchers trained rats to respond by
pressing a lever when they heard a "good" tone. The
rats learnt that if they did this they would be
rewarded with a food pellet. They were taught not to
press the lever when they heard a different "bad"
tone; if they succeeded, they avoided hearing white
noise. Half the rats were then put in unpredictable
cages where lights sometimes turned on or off
unexpectedly, which the researchers thought would
induce a mildly negative mood. All the rats were then
played a tone that was ambiguous, with a frequency
between the good and bad tone. What the team found was
that the "depressed" rats reacted most often to the
new tone as if it were a negative stimulus - as if
they would hear white noise, whereas the happy rats
reacted as if the tone was positive and they would
receive a food reward. Mendl says: "These findings
parallel those of humans and suggest a completely new
method for measuring animal emotions."
Another way to tap into an animal's emotions is to
train them to communicate how they feel. A group of
researchers from London taught pigs to give one
response when they felt normal and a different
response when they were anxious (in this case they
were given a drug designed to induce temporary
anxiety). Not only could the pigs discriminate between
these two states, but later they made the same
"anxious" response when exposed to novel events such
as an unfamiliar pig or a new pig pen. It seems that,
since pigs are smart enough to tell researchers how
they feel, they could be trained to understand that
although a routine husbandry procedure might be
frightening, it could be over relatively quickly and
painlessly.
Procedures such as tail docking in sheep and branding
in cattle are thought to be very painful because
animals respond in a way we associate with pain.
Although highly subjective on our part - we have no
idea what any animal really feels - physiological
studies show that when reacting as if in pain,
animals' stress hormones soar.
Professor Dan Weary, from the University of British
Columbia, argues that conventional husbandry methods
should be rethought on the basis of the animals'
reactions. In one experiment, half the male piglets on
a farm were castrated and the other half were handled
as if they were going to be. Only the pigs who were
castrated made high-pitched squeals, and only at the
time of the castration. Some farmers believe that the
younger the animal, the less painful the operation,
but these pigs squealed no matter what age they were.
The experiment indicates that animals calls are a good
way of assessing their actual pain, rather than the
expectation of pain.
Castration is performed - though rarely in Britain -
because male hormones produced by the testes are
stored in the pigs' body fat and give the meat an
unpleasant taint. But castration, as well as being
time-consuming, reduces the growth rate and results in
poorer quality meat. Weary suggests that pigs should
be injected with hormones that neutralise the sex
hormones - "immunocastration" - instead of being
painfully castrated.
Mendl and his colleagues' are still exploring
"feelings consciousness" in pigs as well as their
capacity for intelligence, in an effort to improve
animal welfare on commercial farms. One of his studies
indicates that pigs become stressed by normal farm
management techniques, such as constantly meeting
unfamiliar individuals, or by being weighed. This
level of stress can make pigs forgetful.
The findings of other researchers support this
conclusion: stress hormones in animals and humans can
disrupt memory. It might seem esoteric - having farms
full of forgetful pigs - but you could argue that the
ability to process information and store memories is
related to conscious experience. On the other hand,
even if pigs have no consciousness, forgetfulness can
lead to damaging behaviour and inefficient husbandry.
For example, animals with impaired memories might
attack individuals because they have forgotten they
know them. This often happens when sows that have
given birth are reunited with their mates; they often
fight vigorously.
Just over nine million pigs are slaughtered each year
in the UK. While many are kept outdoors, unlike other
animals, there are still important welfare problems to
be tackled. Tail-biting and other forms of aggression
are commonplace and may be exacerbated in barren
environments where the pigs have no access to straw.
Sows kept indoors are confined to crates so narrow
that the mother pig cannot turn around during the
lactation period.
By looking at how animals feel as well as what they
think, scientists may be able to enhance animal
welfare. One day, perhaps, scientists such as Mendl
may be able to tell us exactly what matters to a pig.