Our bodies have an instinctual drive to live right from conception, without conscious thought
your heart beats your diaphragm moves up and down to take in air to your lungs, your immune
system constantly checks for infections, your digestive system breaks down food for energy
and your brain takes information about its surroundings to assess dangers in any part
of life.
The latter of that list is what you would likely call the survival instinct, it’s
that nagging feeling about a situation, the disgust at rotting food or even the fear of
some animals.
One such tool we subconsciously use to protect ourselves is our perception of depth.
Is it there from birth or developed over time from experiences, well we all know not to
jump off a cliff?
Even though we haven’t experienced it ourselves, we know it’s not a great move for our life
expectancy.
But how to answer the question of when does the depth perception instinct come into being,
well a scientific team would try to find out by trying to get babies to crawl off a simulated
cliff edge.
My name is John and welcome to the dark side of science.
Our story begins
Every story has a beginning, even the ones that involve trying to coax babies to crawl
off a simulated cliff.
Today our story begins in a place called the behavior farm in the early 1950s and one of
its assistants Yale phd graduate Eleanor Jack Gibson.
The farm was under the control of psychologist Howard Scott Liddell.
Liddell had set up the laboratory modeled on famous behaviorist Pavlov Leningrad labs.
By the 1950s the farm was mainly creating experimental neurosis in the animals.
On it the subjects bred on-site were goats, which allowed access to infants for various
experiments.
Gibson had a burning desire to undertake her own experiments and made use of her time at
the farm to study maternal infant interactions.
One incident on the farm would create the spark for Gibson's future experimental career.
Part of her experiments involved immediately cleaning one of a pair of twin kid goats immediately
after birth, with a detergent before the mother had a chance to lick it, this was to see if
the maternal bond would be interrupted.
Whilst cleaning the kid it’s twin appeared, needing somewhere to place the clean infant
she placed it on top of a camera stand.
Interestingly it stayed neatly keeping its little feet on the stand, this was interesting
it was almost like the animal instinctively knew jumping off was a bad idea.
Gibson would ultimately quit at the behavior farm in 1952 when upon returning from a weekend
off work finding her goat test subjects had been given away as Easter gifts.
Well it is at this point that Gibson would meet her research partner, Richard walk, walk
had arrived at Cornell university as a young professor, the relationship was an odd one
for the era, with walk outranking Gibson being a professor but the female research assistant
was considerably more experienced in science and was older by 10 years.
However, Walk being a professor, gave him the use of lab space, something Gibson hadn’t
been able to secure, it would seem the pair were a good match.
They would kick off this working relationship with a study involving rats in environmental
difference based experiments, where they would be reared in enhanced or impoverished situations,
where the results would be compared to control subjects.
Kind of similar to Harry Harlow's experiments although much less evil.
One of their rat studies involved reading a cohort of subjects in darkness, to be compared
with a control group that had been raised normally.
To make use of the time consuming process walk and Gibson looked to find another use
of their light deprived victims, this would involve testing depth perception.
To test if they possessed depth perception walk Gibson and research assistant Thomas
tighe built a simulated cliff, this was a pane of glass held up by clamps and rods.
To simulate the depth different color wall paper backers were used, with a shallow and
deep side separated by Center board 3 inches high.
This experiment was the visual cliff alpha version so to speak.
Well much to their surprise the dark reared rats acted just like their control counterparts
preferring to go to the shallow side of the apparatus.
The Intriguing results would push walk and Gibson to develop the experiment further into
a more permanent set up.
They looked to make the perceived distance of the drop adjustable and importantly stronger
and robust for a wider range of animals..
The duo looked to test on other species of animals, including goats, pigs, chickens,
dogs, kittens and monkeys, all of which avoided the deep side.
When attempted to be placed on the glass at the deep end most animals attempted to escape
or just refused to put their feet down.
It looked apparent that depth perception was innate, well not quite, when dark reared kittens
were placed on the apparatus they just wandered around not giving two sods about the deep
or shallow side.
But the big question was what would a real human do?
Well it was the late 1950s of course it was time to find some poo and sick machines to
run the experiment onto.
This leads us rather neatly onto the visual cliff experiment.
The Experiment.
Prior to the visual cliff there was not much in the way of depth perception studies in
children, this was Mainly due to the risks involved with simulating heights well at least
before walk and gibson's method.
So the version of the cliff for the baby study was a sheet of Plexiglas that covers a cloth
with a checkerboard pattern.
On one side the cloth is placed immediately beneath the Plexiglas and is thus the shallow
end and the other side is about four feet (1.2 m) lower creating the drop.
Obviously there is no risk to the child but there is an illusion of depth which is accentuated
by the cloth pattern.
The babies would be placed on the central portion of the apparatus and be encouraged
to either the shallow end or across the void by the baby's mother.
The key goal was to find if a baby has to develop depth perception or is it born with
it.
In walk and gibsons 1960 paper they note in their introduction the question of nature
vs nurture:
“Common sense might suggest that the child learns to recognize falling-off places by
experience–that is, by falling and hurting himself.
But is experience really the teacher?
Or is the ability to perceive and avoid a brink
part of the child’s original endowment?”
The experiment started off with a pilot beta test, this involved an 18 month old boy, his
name is unknown, but he crawled to his mother's call on the shallow side.
After reaching it he stood up and shuffled around, when encouraged to cross the deep
side he refused, and when placed on the deep end he showed great stress and anxiety desperately
grabbing the wooded side of the apparatus.
Now with 1 child suitably terrified the duo set about a proper study.
So walk and Gibson recruited 36 infants ranging from the ages of 6-14 months, initially they
were placed on the Center board and observed for a number of minutes.
During this time the mother stood behind a screen.
The first 2 children didn’t try to explore their surroundings and because of the lack
of results for the 3rd subject this method was abandoned.
For the reminder of the subjects the mother would call their child towards both the cliff
and shallow side successively.
Interestingly when called to the deep side most of the infants refused and when seeing
their mothers on the other side of the chasm, showed distress in not being able to reach
them.
Some even patted the glass over the deep end and even though feeling a solid surface, would
refuse to cross, some even moved away to the shallow side, other still just peered into
the deepside.
Out of the 36 subjects only 3 had attempted to go onto the deep side, 27 had moved but
only onto the shallow side, with the remainder of the test subjects refusing to move at all
or just not following their mother's call and just ignoring them.
This is common with infants, they love to ignore their parents.
The mother of the children who had not attempted to venture onto the deepside largely seemed
disappointed, as they had felt they had failed the experiment, but the children had shown
that they were more dependent on their eyesight.
The experiment showed at least in most of the test subjects that depth perception is
pretty much there from when we begin to crawl.
That was the end of the original study that would be published in 1960, but although arguably
answering the question of depth perception and infants, it raised another about maternal
trust, between child and mother.
The 3 that did venture into the deep side creates a new dilemma, we’re they overusing
their fear of the fall with their faith in their mother?
Well this would open the door to a whole wider range of comparative psychological study,
making the visual cliff a classic form of experiment.
One was a study into maternal signaling in 1985 James F source et al, in which the mother
was placed across from the chasm and encouraged the infants using various different emotional
states such as happiness, anger and sadness, happiness yielded the best results.
Another side quest experiment using the visual cliff on infants who were pre locomotive aka
pre crawling, to measure their distress levels when placed on the shallow or deep side.
And spoiler alert the 1970 experiment by JOSEPH J. CAMPOS Et al, babies became rather distressed
in the deep side, hinting at depth perception and thus fear of heights being innate, that
is from birth.
The experiment cemented Walk and Gibson into the annals of experimental psychology, but
now it’s time to see what you think: was it an ethical study?
Children weren’t harmed although possibly a bit distressed, the question has to be raised
at least of a second about informed consent, something the children couldn’t give.
Although no way near as bad it does have some feeling of the baby Albert study or the bobo
doll study.
https://youtu.be/1VPaBcT1KdY
https://stcmpsy.files.wordpress.com/2012/04/gibson-and-walk-original-text.pdf
https://local.psy.miami.edu/faculty/dmessinger/c_c/rsrcs/rdgs/emot/sorce.viscliff.pdf