Re: Article: brain & tools; Well-tooled Primates
- From: "Chapstick" <chapstick@xxxxxxxxx>
- Date: Wed, 21 Feb 2007 18:23:13 -0500
hi
this post did not show up on Google Groups, that i use at work? but it is
on my rr server... --chap
"Chapstick" <chapstick@xxxxxxxxx> wrote in message
news:45dbb6db$0$16668$4c368faf@xxxxxxxxxxxxxxxxx
Week of Feb. 10, 2007; Vol. 171, No. 6 , p. 88
http://www.sciencenews.org/index.asp
(article available to subscriber's only... by the way.. bruce bower is a
great writer...--chap)
Well-Tooled Primates
The evolutionary roots of our technological prowess may run deep
Bruce Bower
In a lab in Japan, a macaque monkey eyes a small, plastic rake and
performs an act that his wild brethren would never dream of doing. The
animal grasps the utensil by its handle and extends it toward a food
pellet placed beyond his reach. Slowly, the monkey manipulates the rake so
that it drags the morsel close enough that he can grab it and pop it into
his mouth. Researchers in the lab suspect that macaques possess an innate
neural capacity for manipulating objects that encourages tool use, even if
such behavior occurs rarely in the wild.
STONE STRUCK. A researcher demonstrates how to use one stone to pound
flakes off another, yielding a sharpened edge in a style developed by our
Stone Age ancestors.
Stone Age Inst.
Meanwhile, at Indiana University in Bloomington, six people smash rocks
together in the name of science. At the request of anthropologist Dietrich
Stout, each participant chooses a pair of stones from a selection on a
cart and strikes them together, again and again, trying to create sharp
flakes suitable for use as cutting tools. After four 1-hour sessions, the
budding toolmakers produce sharp flakes that look much like the stone
tools made by human ancestors as many as 2.5 million years ago.
Brain scans obtained from those participants before and after the
toolmaking sessions and from the monkeys as they use the plastic rakes
show increases in activity in the same brain area. Furthermore, no
activity emerges in the human toolmakers' neural regions that control
planning and memory, intellectual faculties often considered crucial to
the evolution of toolmaking.
These related findings support the theory that the evolution of neural
areas devoted to object manipulation by ancient primates paved the way for
stone-tool making by human ancestors. Our ancient forerunners didn't think
up these technological advances so much as explore their way into them,
according to this perspective. The distinction is important because rule
following and planning-not to mention self-awareness, imitation, and
language skills-flowered after prehistoric humans attained toolmaking
expertise.
Researchers who subscribe to these ideas theorize that modern humans are
neither blank slates nor carriers of a batch of instincts unique to our
species. Instead, via language and cultural traditions, people have
collectively molded a shared primate-evolutionary heritage for their own
purposes.
"Fairly ancient brain systems were elaborated in new ways when human
ancestors began making and using stone tools," says Stout, now at
University College, London. "This process relied on an education of
attention, not intellect."
Monkey business
Although monkey species in some parts of the world spontaneously use
sticks or other objects as tools, Japanese macaques seldom do. Yet it took
Atsushi Iriki and his colleagues at the RIKEN Brain Science Institute in
Saitama, Japan, only about 2 weeks to train adult Japanese macaques to
snag food with a rake.
This experience changes the structure of these monkeys' brains, Iriki's
team found. The alterations then spur the animals to think and act in new
ways that have surprising connections to human thought and behavior, Iriki
holds.
Iriki suspects that the brain changes tap into "silent precursors of human
intelligence in the tool-using monkey brain." He describes his research in
the Dec. 2006 Current Opinion in Neurobiology.
A decade ago, Iriki and his coworkers used hair-thin electrodes implanted
in monkeys' brains to identify neurons in one parietal area, near the
brain's midpoint, that vigorously responded to both visual and bodily
sensations. This area also contains what are called mirror neurons, nerve
cells that react equally strongly when the animal executes an action and
when it observes another animal perform the same action.
Mirror neurons may make it possible to imitate others' behavior (SN:
9/9/06, p. 163: http://www.sciencenews.org/articles/20060909/fob1.asp).
Before training macaques to use the rakes, Iriki's team noted that
electrical discharges of other parietal cells peaked when an animal looked
at the hand it used for reaching out and grabbing objects. After a macaque
learned to use the rake, the same cells spewed impulses when the animal
looked anywhere along the trajectory extending from its rake-holding hand
to the end of the tool.
This neural shift indicates that macaque rake users incorporate the tool
into an internal representation of their bodies and their parts, Iriki
proposes.
As a result, tool users gradually come to mentally regard their hands and
arms, and then their entire bodies, from a third-person perspective, he
says. This achievement boosts the capacity to scrutinize and imitate
others' actions.
In support of this idea, Iriki now finds that the 2-week-long rake
training stimulates important brain changes in adult monkeys. His team
stained and microscopically examined parietal cells from the brains of
five trained monkeys and compared them with corresponding cells from four
untrained monkeys.
In the trained group, parietal cells connected to cells in two brain areas
that weren't accessed by those cells in untrained animals. In people, one
of those areas, which is near the parietal cortex, fosters a sense of body
image and of self, some research has found. The other area, in the frontal
brain, contributes to mental flexibility in carrying out familiar tasks.
Tool use by monkeys may even promote a behavior that Iriki regards as an
evolutionary precursor of language. When monkeys were first trained to
rake in food and then to produce cooing sounds to ask for food, they
spontaneously began to emit two acoustically distinctive coos-one for food
and another requesting a rake to retrieve food. These findings suggest
that human ancestors parlayed stone-tool pursuits into advances in speech,
using sounds to label various objects, Iriki asserts.
"Their tool use could have contributed to the emergence of perceiving
meaning in language and other higher cognitive functions," he suggests.
Rock solid
As Stout pored over human-brain data from his novice stone-tool makers
last year, Iriki's studies came to mind. The parietal neighborhoods
activated in rake-trained monkeys had geared up when Stout used
positron-emission tomography to monitor the volunteers' brains' energy use
during their toolmaking sessions.
IMPLEMENTING COLORS. Brain images show neural regions that became
substantially more active as study participants gained experience at
making stone tools. The highest activity appears in red.
Stout
However, stone-tool making ignited brain regions aside from the seemingly
ancient network that Iriki observed in macaques, Stout reports in a 2007
Neuropsychologia (vol. 45, issue 5). Toolmaking practice enlivened brain
areas that regulate handgrips and that mediate visual attention in people.
An additional parietal area displayed pronounced activity as toolmakers
gained skills. Studies directed by neuroscientist Guy A. Orban of K.U.
Leuven Medical School in Belgium suggest that this region is present in
people, but not in apes or monkeys. It boosts three-dimensional perception
and enhances the clarity of moving images-handy attributes for toolmakers.
For Stout, these findings suggest that ancient toolmaking rested on
extensive practice that improved people's visual analysis of rocks and the
fluidity of the actions needed to produce sharp flakes. Earlier work
indicated that novices learned by doing and by getting feedback from
experienced workers, not by following rules (SN: 4/12/03, p. 234:
Available to subscribers at
http://www.sciencenews.org/articles/20030412/bob10.asp).
Neuroscientist Scott H. Frey of the University of Oregon in Eugene sees
Stout's results as consistent with studies of more-mundane tool use. Using
functional magnetic resonance imaging to track blood-flow changes in the
brain, Frey's group has found that people who are planning to, say, eat
with a spoon or pound with a hammer galvanize a widespread network of
regions in the left brain, including frontal and parietal tissue.
When actually using such implements, the same individuals display activity
largely relegated to the parietal areas emphasized by Stout. "These
regions are involved in transforming sensory information into motor
commands," Frey says.
He suspects that expert stone-tool makers also call on a broad network of
left brain structures, including frontal areas linked to planning and
memory.
Psychologist Arthur Glenberg of the University of Wisconsin-Madison
suggests that further research examine whether parietal responses are
stimulated by stone-tool making itself or by practicing any set of
goal-directed actions.
Changing spaces
If Iriki and Stout are right, then our prehistoric ancestors didn't invent
stone tools out of evolutionary whole cloth. Instead, groups bound by
cultural traditions turned a humble neural inheritance into a unique
aptitude for toolmaking and other technological pursuits.
That scenario rings true to linguist Stephen C. Levinson of the Max Planck
Institute for Psycholinguistics in Nijmegen, the Netherlands. He and his
colleagues study how people perceive their locations and orientations
relative to those of external objects and plan routes from one spot to
another. This mental faculty, known as spatial cognition, contributes to
toolmaking and tool use.
In the Nov. 14, 2006 Proceedings of the National Academy of Sciences,
Levinson's group asserts that all people innately consult environmental
cues to locate themselves in space and to navigate from point A to point
B. However, assumptions built into some cultures and languages transform
this innate tendency into a preference for using oneself, rather than
one's surroundings, as a spatial reference point, the researchers say.
The researchers emphasize that some languages, including English, tend to
describe object locations in terms relative to an observer's viewpoint,
such as front, back, right, and left. Other languages generally use terms
for absolute directions-north, south, east, and west-or refer to familiar
landmarks.
In one experiment, the researchers studied 12 adults and 12 children, ages
8 to 10, who spoke Dutch, a language that, like English, uses mainly
relative spatial terms. Another 12 adults and 12 children came from an
African hunter-gatherer group that typically uses absolute spatial
descriptions.
Each volunteer sat in front of a table and watched an experimenter
alongside the table place a token under one of five cups positioned like
dots on a die-two on the bottom, one in the middle, and two on top.
Participants then moved to the opposite side of the table and to another
set of cups and indicated where they thought a second token might be
hidden.
In a series of trials, Dutch adults and kids rapidly learned where the
tokens were and made few errors if the tokens in the two tests maintained
position relative to a participant's viewpoint, such as starting out on
the bottom left-hand side and again being bottom left after the volunteer
moved to the new viewing position. However, their performance declined
sharply if the tokens maintained absolute position, such as being located
under the northwestern cup-which started out on the lower left and then
was upper right after the participants repositioned.
In contrast, the hunter-gatherers excelled at finding hidden tokens that
maintained absolute position and stumbled on the other condition.
The researchers then administered a simpler version of the hidden-token
test to 12 German 4-year-olds attending preschool as well as 5 orangutans,
7 gorillas, 7 pygmy chimpanzees, and 11 common chimps. Although German
adults tend to use relative spatial terms, both the preschoolers and the
apes located tokens more readily and accurately when using environmental
cues-either absolute or landmark based.
Levinson's team theorizes that apes and people possess an innate tendency
to navigate by tracking features of their surroundings. An
observer-centered viewpoint develops slowly during childhood only when
cultivated by language and culture, the researchers propose.
Psychologist Nora S. Newcombe of Temple University in Philadelphia
expresses skepticism about that conclusion. Mobile individuals skillfully
use both viewer-centered and environment-centered spatial strategies when
necessary, she says. For instance, landmarks are essential to speakers of
relative languages when they're planning alternative routes to a
destination and to speakers of absolute languages when, on occasion, dead
reckoning leads them astray.
Similarly, researchers will need to use a variety of strategies as they
wend their way along the path from rake-wielding monkeys to tool-producing
people. There's still a long distance to go, but a few neural landmarks
now light the way.
.
- Prev by Date: Freeze 'condemned Neanderthals'
- Next by Date: Re: Spirit Cave Man
- Previous by thread: Re: Article: brain & tools; Well-tooled Primates
- Next by thread: Freeze 'condemned Neanderthals'
- Index(es):
Relevant Pages
|
|
