英文阅读：大象拥有超强记忆力？
都说大象记忆力超群，他们能分辨出训象人的味道，即使分开多年。那么，大象的记忆力有传说的那么神奇吗?下文就将为您揭开端倪。Nearly a century later, extensive observations have confirmed that
elephants indeed remember injuries and hold grudges against their abusers. For
example, one study of African elephants found that the animals react negatively
to the sight and scent of clothing worn by members of a nearby Maasai tribe of
people . Why the sour grapes? Maasai men spear elephants as a
customary display of their masculinity.
Anecdotal evidence also suggests that elephants remember trainers or
keepers who mistreated them even after years of separation [source: National
Geographic]. Similarly, scientists have linked elephant raids on villages in
Uganda to a form of post-traumatic stress disorder . The experts
believe that the elephants lashed out because the growing human population was
taking over elephant territory, forcibly separating some elephants from their
close-knit family units .
Elephants are far more thoughtful mammals than their popular circus
entertainer personas imply. In the wild, they follow formalized family
structures with older females, or matriarchs, at the top. Daughter elephants
always stick close with their mothers, forming families. Male offspring leave
the family at around 14 years of age, or whenever they reach sexual maturity,
described as being in musth. From there, males join groups of other male
elephants, which they'll periodically leave for mating purposes. During
droughts, multiple elephant families consisting of the females and their calves
may congregate to form bond groups and share resources.
With all of this coming and going, elephants have many forms of
communication to keep up with each other. One method for spatially locating
other elephants is through the bundles of nerve sensors in their feet called
Pacinian corpuscles . The corpuscles translate seismic
vibrations coming from the ground into a nerve impulse that sends a message to
the brain about the source and direction of the vibrations. Even their toenails
contain nerves that discern where sounds come from .
But what's going on in those noggins that makes elephants famous for their
memory? Next, we'll dissect the elephant brain to see whether or not it's just
peanuts up there.
Scientists haven't been able to measure elephants' intelligence precisely.
Nevertheless, for decades, experts have observed the pachyderms' behavior and
concluded that they rank among the smartest in the animal kingdom. That said,
the theory of elephants never forgetting is an exaggeration, but doesn't stray
terribly far from the truth.
Elephants have the largest brains by mass of all mammals, weighing in at a
hefty 10.5 pounds (4.7 kilograms) for an adult . While
we can't judge how effectively a brain works based solely on its size, it can
offer a decent approximation and give us a hint as to the power of elephant
memory. One conventional way of estimating an animal's intelligence is examining
the encephalization quotient (EQ). The EQ compares the actual size of an
animal's brain against the size scientists would project its brain to be based
on body weight. To better understand this measurement, think of an apple and an
avocado. Both fruits are relatively the same size, but an apple has tiny seeds,
while an avocado's seed resembles a golf ball.
The logic follows that the smaller the ratio of brain to body mass (think
of the apple example), the dumber the animal and vice versa. For instance,
people have an average EQ above seven, while pigs have an EQ of around .27
.
Elephants score relatively high on this scale, coming in at a cross-species
average of 1.88 . For comparison, chimpanzees have an EQ
of 2.5. Female elephants, the leaders of the herds, often have greater EQs than
males. This is probably linked to the matriarchal social structure of elephant
herds. Studies have also found that the elder female elephants exhibit signs of
a superior memory, alerting the herd if a familiar danger arises or an old
feeding site is recognized .
The olfactory, or smell-related, region of an elephant's brain is extremely
developed in relation to its other senses. Elephants can distinguish between the
urine scents of up to 30 female relatives, even if they've been separated for
years . This trait helps elephants stay together when traveling
in large herds, with the urine serving as a bread crumb trail for the nose -- or
trunk in this case.
While elephants' utilitarian memories help them retain essential survival
information, they also allow these animals to recognize the past. Elephants'
show signs of grief over dead relatives such as gently touching the corpses with
their feet and caressing the bodies with their trunks .
In an experiment that involved showing different sets of objects to a family
unit of elephants, the group responded most prominently to bones and tusks once
belonging to a relative .
An elephant's memory doesn't stow each detail of every stimulus ever
encountered. Instead, the brain encodes what's necessary for survival, such as
food location and family identification, in the same way that our short-term
memory systems selectively discard or transfer data to our long-term storage
. And just like those moments that impact our lives the most,
the contents of elephants' functional memories are preserved for future
retrieval.
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