everyone has had some kind of an
experience feeling something kind of
like fear of heights and it makes
perfect common sense that we shouldn't
jump over the edge of a drop-off because
it's dangerous and if it's dangerous
then we should probably be afraid of it
probably exactly how and when this
hypothetical fear develops makes for
pretty gleeful research inside dr. Karen
Adolf's lab we're discovering some
surprising things that are flying in the
face of you know how people have studied
locomotion for the last hundred years
including what babies do and feel when
they're on a Ledge so the story about
fear of heights is that there was a very
very famous classical study in
developmental psychology by Gibson and
walk in 1960 that showed that human
infants an instance of a number of
different species will avoid crossing
over an apparent drop-off on what they
called a visual cliff as soon as the
baby to move about it can be observed in
the same way other animals it's a glass
table and on one side there's a
checkerboard pattern surface right under
the glass the other side of the table
the patterned surface is way down on the
floor so visually it looks like a big
three-foot drop-off so when human babies
first begin crawling most of them will
crawl over the apparent drop-off but
after several weeks of curling
experience then they'll begin to refuse
to crawl over the drop-off and the
conventional interpretation of this was
that infants are avoiding the drop-off
because they're afraid of heights
backing away vertically she's not
interested she wants no part of that
side the experiment became the shaky
foundation for the myth that crawling
and Nate Lee teaches us to fear Heights
maybe it's avoid going over the drop-off
because they're afraid of heights how do
we know they're afraid of heights
because they avoided curling over the
drop-off so as you may have noticed the
argument is circular as it happened the
visual cliff was a better test of an
infant's depth perception not their fear
of heights and if you look closely you
may have actually noticed that the
babies don't look particularly scared
perfectly safe surface of support so
after one trial human infants cleverly
figure this out and then they will crawl
over the drop-off so how do you really
test if a baby's scared of heights you
can test babies at the edge of a real
cliff where there's no safety glass it's
just an actual drop off and the drop off
can be adjustable so it can be little or
really really big and why stop there
inside dr. Adolf's infant action lab
babies are tested on a variety of
apparatuses in tests Maeby's at the edge
of the slope so it can be super super
super crossing bridges that are white or
narrow over a surface of support and so
on if there's no safety glass you can
test the same baby dozens on dozens and
dozens of trials in the same session and
that means that you can determine for
each individual infant when they think
that that surface is safe and when they
think it's risky within a couple of
degrees of accuracy like two degrees of
accuracy for a slope doctor Yadav has
spent 25 years running tests like these
and the resulting datasets are both
convincing and adorable infant spend
most of each trial right at the edge of
the precipice they're reaching their arm
down over the drop-off they are putting
their little feet or their little hands
on the bridge and taking little tiny
steps at the edge and all the way all
they're doing it with either neutral or
positive facial expressions what's more
surprising is how their approach changes
as they learn different forms of
locomotion so what happens is that when
babies first begin crawling they'll
crawl right over the edge that over
weeks of crawling their responses get
more and more accurate until finally
they're an adult like levels so that
they can tell precisely whether a slope
is safe for pulling or whether a
drop-off is safe for crawling but then
the next week when these babies stand up
and face these same drop-off scene slope
team apparatus now at the new Walker
they walk right over the edge so in fact
there seems to be four learning curves
and development as babies learn to sit
there to crawl as they learn to cruise
and then fine
as they learn to walk so if they were
afraid of heights you should just be
afraid of heights in the rain and on a
train and in a tree you shouldn't see
four separate learning curves so if
babies aren't learning to be afraid of
heights what are they learning I think
that what babies are learning over weeks
of sitting crawling cruising walking as
they're learning to perceive the
relations between their bodies and the
environment they're discovering what's
possible and what's just a little too
far and you can learn that without
feeling any sort of fear at all in fact
owner Gibson the person who first
invented the visual cliff robe later in
her life as a goat is peering over the
edge of a steep crack it knows not to
walk off the edge and she said I don't
think of feeling any emotions at all it
just knows not to go and that's what
we're seeing a baby who probably know
not to go probably for science friday
and Luke grasp