This
little piggy has depression
Independent UK
February 16, 2005
Scientists now say they can tell a happy
animal from a sad one. But should this
discovery inform the way we look after
them?
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.
