Do you have a fear of heights? If you do, how long have you had that fear of heights? If you are anything like the children in psychology’s Visual Cliff experiment, you might have been holding onto that fear since you were a baby.
What Is the Visual Cliff Experiment?
The 1960 Visual Cliff experiment is the most famous look at how depth perception develops. The visual cliff experiment is a great look into how the fear of heights develops and how psychologists used different forms of research to observe that development.
What Is the Purpose of the Visual Cliff Experiment?
The researchers behind this experiment wanted to learn whether or not depth perception, or our ability to perceive three dimensions, is an innate skill or something that is learned. This speaks to one of the biggest debates in psychology: nature vs. nurture. Are our skills learned, or are they set in stone through genetics? Are our fears learned, or are we doomed to have certain fears due to our family history?
For this reason, researchers chose to work with infants of varying ages as well as baby animals: rats, calves, and cats. What does the visual cliff phenomenon suggest about the nature versus nurture debate in human development? The results of the experiment, the researchers believed, could show if there was a certain age in which depth perception was learned or whether it was a skill present in every child that was born.
Who Conducted the Visual Cliff Experiment?
Psychologists E.J. Gibson and R.D. Walk put together the visual cliff experiment, which was used to measure depth perception in infants.
How Did the Visual Cliff Experiment Work?
The psychologists developed a test in which babies were placed on a large table of Plexiglass that was about a foot off the ground. One side of the plexiglass was covered in a tiled pattern that you might see on any floor. The other side of the plexiglass was left as it is – completely transparent. The pattern continued on the floor below the plexiglass.
Babies or animals without depth perception may not perceive the depth between the two blocks of the tiled pattern. They would see the pattern as continuous and could walk freely over the Plexiglass without fear. With depth perception, things get tricky. The way that the experiment was set up gave the illusion of a visual “cliff” without putting the babies in danger.
The researchers put the baby on the side with the first side of the Plexiglass and their mother on the other side. If the baby were to crawl to the mother, they would have to make a decision about whether or not to cross the visual cliff. If the baby was hesitant, thought the researchers, then it was presumed that the baby could perceive the depth and was scared to fall off the visual cliff.
The Visual Cliff in Animals vs. Babies
In order to get a wider perspective on the development of depth perception, researchers conducted a similar version of the visual cliff experiment with animals.
Like babies, researchers used infant animals. These animals included participants who were just a day old. These early studies suggested that depth perception was innate in most animals – even the youngest participants might avoid crossing the “visual cliff” and stay on the side that appeared to be safer.
But the results of this study, like the results of the studies focused around infants, aren’t so cut and dry. Researchers also took note of whether some of the participants were raised in the dark or raised in the light. The kittens that were raised in the dark were less likely to have developed depth perception than the ones raised in the light. Rats weren’t hesitant to run across the glass cliff, as they rely on smell and touch more than vision. Even when researchers studied animals, they found that motivation isn’t as simple as what you see.
Visual Cliff Experiment Results
What happened when the babies were put to the task of walking across the cliff? There isn’t one solid answer. Some babies refused to walk across the visual cliff. Others could feel that the glass was able to support them on the path to their mother but still refused to cross out of fear. But most of the babies (27 out of 36 in the experiment) walked to their mother without any issues.
What did these findings say about depth perception? At the time, researchers believed that the results told a story about depth perception. They believed that depth perception was something that wasn’t developed until later. If the babies easily crawled to their mothers, they must not have depth perception, right?
Well, this isn't exactly correct.
Are The Visual Cliff Experiment Results Still Relevant?
Since 1960, this experiment and similar variations have been conducted to take a deeper look at how babies processed what was going on around the glass cliff. These researchers have realized that there is a lot more that goes into the baby’s choice to crawl than just visual maturity. While some say that the experiment has been "debunked," psychologists may argue that this is exactly how experiments are meant to work. As we learn more about conducting these experiments, the more we learn about psychology.
The results from studies as recent as 2014 have changed the way that we look at the results and depth perception in general. Let’s look at why the babies of the 1960s may have behaved in the way that they did, even if they did have depth perception.
Feeling the glass underneath them
The tactical sensation of the glass, even where the illusion of the “cliff” began, may come into play. If the baby felt that the glass supported them, they might have been more comfortable walking over it.
Reassurance from their mother
In the original experiments from 1960, the baby’s mother on the other side of the plexiglass used a toy as a stimulus to motivate the babies across the visual cliff. But many have pointed out that there is more to the baby’s motivation than just the toy. Not only did the babies rely on their sight and sense of touch to reassure them that the glass was safe, but they also relied on the facial expressions of their mother. The babies who saw a happy, smiling mom on the other side of the “cliff” were more likely to crawl across the cliff without fear.
Why might a baby not want to crawl across the visual cliff? The answer seems simple – fear of heights. The baby, like anyone approaching a cliff, does not want to fall and hurt themselves.
But as anyone who has been around babies knows, they don’t always have a sense of fear. A baby might put their hand on a hot stove or stick their fingers in a light socket without fear. Is the fear of heights the only innate fear in humans?
Not exactly. Researchers have taken a look at the experience of babies who participate in visual cliff studies and found something interesting. Babies who learned to crawl early on were more likely to cross the glass than babies who learned how to crawl later in their development. When babies first learn how to crawl, they quickly find out that they risk falling over or getting a boo-boo. Over time, they face that fear and learn when those consequences might actually take place. Experience crawling, including encountering situations in which the baby might use their sense of touch or a mother’s reassurance to make a decision, plays a role.
Lucky for psychologists, there are ways that we can measure whether a person experiences fear. Our body responds to fear or threatening situations in a variety of ways: our breath and heartbeat become faster, our pupils change, or we might sweat. In more recent years, psychologists have used these metrics to assess how depth perception or fear plays into the baby’s decision to crawl over the visual cliff.
What they found was that very young infants (as young as three months old) experienced some sort of biological reaction to the visual cliff. These babies just happened to “face their fears” even after perceiving the depth on both sides of the cliff.
All in all, researchers now believe that depth perception can be found in the youngest of infants, the fear of heights is not innate to all humans.
Visual Cliff Experiment Conclusion
There is a lot that goes into this study: the development of sight, fear, experience walking, and even the facial expression of the mother or researcher on the other side of the “cliff.” The original experiments on the visual cliff didn’t exactly account for all of this when the research was conducted and the findings were published. Keep this in mind as you continue to learn about psychology and the experiments that have shaped our understanding of the world around us. Human beings are complex, and our motivation cannot be attributed to just one factor, innate or otherwise.