Young children rely on one sense or another, not a combination,
studies find

Unlike adults, children younger than eight can't integrate different
forms of
sensory input to improve the accuracy with which they perceive the
world around
them, according to a pair of studies reported online in Current
Biology on May
1st.

The findings suggest that the perceptual systems of developing
children might
require constant recalibration-through the use of one sense to fine-
tune another
and vice versa, according to the researchers. They might also reflect
inherent
limitations of the still-developing brain.

"Kids have to stay calibrated while they are growing all the time-
their eyes get
farther apart and their limbs longer," said David Burr of Università
Degli Studi
di Firenze, who led one of the studies. Under these conditions, "they
may use
one sense to calibrate the other."

"It could be adaptive for humans not to integrate sensory information
while they
are still developing," agreed Marko Nardini of the Centre for Brain
and
Cognitive Development at Birkbeck College, University of London. "But
there
might also be constraints on what children can do. It's possible that
brain
development needs to take place to make integration possible." Nardini
led the
other of the two studies with colleagues at Oxford University's Visual
Development Unit.

The studies followed earlier findings that showed that adults can
integrate
information obtained visually with that obtained through the sense of
touch,
optimally weighting each sense according to its reliability in a given
situation.

In the new study, Burr's team first had children complete a task in
which they
were asked to judge which of two blocks was taller on the basis of
touch or
visual information or some combination of the two. In another set of
experiments, the children were asked to judge which of two bars was
oriented
more counterclockwise.

Their studies revealed that the ability to combine sensory information
doesn't
develop in children until about the age of eight. Prior to that,
integration of
visual and touch-derived spatial information (also known as haptic
information)
is far from optimal, they reported, with either vision or touch
dominating
totally even in conditions where the dominant sense is far less
precise than the
other. However, they found no evidence that either vision or touch
acts as a
"gold standard," always dominating the other.

In the task involving size discrimination, their results fit with the
old notion
that 'touch educates vision," Burr noted. "At first it looked like
that was what
was happening," he said, "but in the case of orientation tasks, the
opposite
occurred. It's doesn't just go in one direction."

At eight to ten years of age, children's integrating skills become
optimal, as
in adults, they showed.

Nardini's group made a similar discovery while studying the navigating
skills of
children versus adults. Navigation depends both on attending to visual
landmarks
and on keeping track of one's own movement (self-motion), they
explained.

In their study, children and adults attempted to return an object to
its
original place in an arena, using visual landmarks only, non-visual
self-motion
information only, or both.

Adults-but not four- to five-year-olds or seven- to eight-year-olds-
got better
at the task when both information sources were available, they found.

Further observations supported the notion that adult behavior was best
explained
by sensory integration, while children's behavior suggested they were
alternating between using the two types of information. The findings
led them to
conclude that people can integrate spatial cues nearly optimally to
navigate,
but that this ability depends on an extended developmental process.
" We already know that kids are more liable to get lost and
disoriented,"
Nardini said, "but this study suggests that a specific reason for that
is poor
ability to integrate different kinds of spatial information."

It might also explain how adults manage to improve on all sorts of
tasks over
time, he added. "It demonstrates how adults build on their perceptual
abilities
not just by improving individual senses, but also by getting better at
integration."

Source: Cell Press
http://www.physorg.com/news128862346.html