Visual cliff
Encyclopedia
The visual cliff apparatus was created by psychologists Eleanor J. Gibson
and R.D. Walk to investigate depth perception
in human and animal species. This apparatus allowed them to experimentally adjust the optical and tactical stimuli associated with a simulated cliff while protecting the subjects from injury. The visual cliff consists of a sheet of Plexiglas that covers a cloth with a high-contrast checkerboard
pattern. On one side the cloth is placed immediately beneath the Plexiglas, and on the other, it is dropped about 4 feet below. Since the Plexiglas supports the weight of the infant
this is a visual cliff rather than a drop off. Using a visual cliff apparatus, Gibson and Walk examined possible perceptual differences at crawling age between human infants born preterm and human infants born at term without documented visual or motor impairments.
was concealed in the design of the visual cliff Gibson and Walk conducted a number of control experiments. In one of the studies they eliminated reflections from the glass by lighting the patterned surfaces from below the glass (to accomplish this they dropped the pattern below the glass on both sides, but more on one side than on the other). The rats being tested still consistently chose the shallow side. As a test of the role of the patterned surface they replaced it on either side of the centerboard with a homogeneous gray surface. Confronted with this choice, the rats showed no preference for either the shallow or the deep side. They also eliminated the optical difference between the two sides of the board by placing the patterned surface directly against the undersurface of the glass on each side. The rats showed no preference to either side.
younger than crawling age on the visual cliff. This study found that the infants exhibited distress less frequently when they were placed on the deep side of the apparatus in contrast to when they were placed on the shallow side. Meaning that prelocomotor infants can discriminate between the two sides of the cliff.
as well. A few of these species included rats, cats, turtles, cows, and chickens.
do not depend upon visual cues like some of the other species tested. Its nocturnal habits lead it to seek food largely by smell. When moving about in the dark, it responds to tactual cues from its stiff whiskers (vibrissae) located on its snout. Hooded rats tested on the visual cliff show little preference for either side of the visual cliff apparatus as long as they could feel the glass with their vibrissae. When placed upon the glass over the deep side, they move about as if there was no cliff.
. The late Robert M. Yerkes of Harvard University found in 1904 that aquatic turtles have somewhat worse depth-discrimination than land turtles. On the visual cliff one might expect an aquatic turtle to respond to the reflections from the glass as it might to water and prefer the deep side for this reason. They showed no such preference, 76 percent of the aquatic turtles crawled onto the shallow side. The large percentage that choose the deep side suggests either that this turtle has worse depth-discrimination than other animals, or that its natural habitat gives it less occasions to "fear" a fall.
to perceive a visual cliff was tested by NA Arnold et al. Twelve dairy heifers were exposed to a visual cliff in the form of a milking pit while walking through a milking facility. Over this five day experiment the heifers’ heart rates were measured along with the number of times they stopped throughout the milking facility. Dairy heifers in the experimental group were exposed to a visual cliff while dairy heifers in the control group were not. The experimental group was found to have significantly higher heart rates and stop more frequently than the heifers in the control group. Depth exposure did not have any effect on cortisol levels or the ease of handling of the animals. These findings provide evidence of both depth perception and acute fear of heights in cows. This may lead to a reorganization of the way milking factories function.
responded to the visual cliff when tested by PR Green et al. As the depth of the visual cliff below the chicks was increased the latency for the chick to move towards the incentive, another chick on the far side of the apparatus, was increased while the speed at which they moved decreased. On the other hand chicks that were given the same incentive to jump over a visible edge onto the deep side of the apparatus were less inclined to move at all depths. This illustrates that the absolute depth of a surface and the relative depth of an edge affect behavior differently in chicks.
. Most rely on visual cues for depth perception. The rat however, relies on olfactory and tactile cues (being nocturnal) but will fall back on vision when needed. Next, the experimenters wanted to find out which visual cues played a decisive role in depth perception. Using dark-reared animals, they concluded motion parallax is an innate cue for depth discrimination, whereas responses to differential pattern-density may be learned later.
Eleanor J. Gibson
Eleanor J. Gibson was an American psychologist. Among her contributions to psychology, the most important are the study of perception in infants and toddlers...
and R.D. Walk to investigate depth perception
Depth perception
Depth perception is the visual ability to perceive the world in three dimensions and the distance of an object. Depth sensation is the ability to move accurately, or to respond consistently, based on the distances of objects in an environment....
in human and animal species. This apparatus allowed them to experimentally adjust the optical and tactical stimuli associated with a simulated cliff while protecting the subjects from injury. The visual cliff consists of a sheet of Plexiglas that covers a cloth with a high-contrast checkerboard
Checkerboard
A checkerboard or chequerboard is a board of chequered pattern on which English draughts is played. It is an 8×8 board and the 64 squares are of alternating dark and light color, often red and black....
pattern. On one side the cloth is placed immediately beneath the Plexiglas, and on the other, it is dropped about 4 feet below. Since the Plexiglas supports the weight of the infant
Infant
A newborn or baby is the very young offspring of a human or other mammal. A newborn is an infant who is within hours, days, or up to a few weeks from birth. In medical contexts, newborn or neonate refers to an infant in the first 28 days after birth...
this is a visual cliff rather than a drop off. Using a visual cliff apparatus, Gibson and Walk examined possible perceptual differences at crawling age between human infants born preterm and human infants born at term without documented visual or motor impairments.
The Original Visual Cliff Study
Dr. Gibson and Dr. Walk (1960) hypothesized that depth perception is inherent as opposed to a learned process. To test this, they placed 36 infants, 6 to 8 months of age, on the shallow side of the visual cliff apparatus. The researchers found that 27 of the infants crawled over to their mother on the “deep” side without any problems. A few of the infants crawled but were extremely hesitant. Some infants refused to crawl because they were confused about the perceived drop between them and their mothers. The infants knew the glass was solid by patting it, but still did not cross. In this experiment, all of the babies relied on their vision in order to navigate across the apparatus. This shows that when healthy infants are able to crawl, they can perceive depth.Bias Elimination
To eliminate the notion that a hidden biasBias
Bias is an inclination to present or hold a partial perspective at the expense of alternatives. Bias can come in many forms.-In judgement and decision making:...
was concealed in the design of the visual cliff Gibson and Walk conducted a number of control experiments. In one of the studies they eliminated reflections from the glass by lighting the patterned surfaces from below the glass (to accomplish this they dropped the pattern below the glass on both sides, but more on one side than on the other). The rats being tested still consistently chose the shallow side. As a test of the role of the patterned surface they replaced it on either side of the centerboard with a homogeneous gray surface. Confronted with this choice, the rats showed no preference for either the shallow or the deep side. They also eliminated the optical difference between the two sides of the board by placing the patterned surface directly against the undersurface of the glass on each side. The rats showed no preference to either side.
Preterm Infants
Sixteen infants born at term and 16 born preterm were encouraged to crawl to their caregivers on a modified visual cliff. Successful trials, crossing time, duration of visual attention, duration of tactile exploration, motor strategies, and avoidance behaviors were analyzed. A significant surface effect was found, with longer crossing times and longer durations of visual attention and tactile exploration in the condition with the visual appearance of a deep cliff. Although the two groups of infants did not differ on any of the timed measurements, infants born at term demonstrated a larger number of motor strategies and avoidance behaviors by simple tally. This study indicates that infants born at term and those born preterm can perceive a visual cliff and change their responses accordingly.Prelocomotor Infants
Another study, by Joseph J. Campos, measured the cardiac responses of human infantsInfant
A newborn or baby is the very young offspring of a human or other mammal. A newborn is an infant who is within hours, days, or up to a few weeks from birth. In medical contexts, newborn or neonate refers to an infant in the first 28 days after birth...
younger than crawling age on the visual cliff. This study found that the infants exhibited distress less frequently when they were placed on the deep side of the apparatus in contrast to when they were placed on the shallow side. Meaning that prelocomotor infants can discriminate between the two sides of the cliff.
Maternal Signaling
James F Sorce et al. tested to see how maternal emotional signaling affected the behaviors of 1-year-olds on the visual cliff. To do this they placed the infants on the shallow side of the visual cliff apparatus and had their mothers on the other side of the visual cliff eliciting different emotional facial expressions. When the mothers posed joy or interest most of the babies crossed the deep side but if the mothers posed fear or anger, most of the babies did not cross the apparatus. In the absence of depth, most of the babies crossed regardless of the mother’s facial expressions. This suggests that babies look to their mother’s emotional expressions for advice most often when they are uncertain about a situation.The study in different species
The visual cliff was not only tested on human infants, it was applied to other speciesSpecies
In biology, a species is one of the basic units of biological classification and a taxonomic rank. A species is often defined as a group of organisms capable of interbreeding and producing fertile offspring. While in many cases this definition is adequate, more precise or differing measures are...
as well. A few of these species included rats, cats, turtles, cows, and chickens.
Rats
RatsRat
Rats are various medium-sized, long-tailed rodents of the superfamily Muroidea. "True rats" are members of the genus Rattus, the most important of which to humans are the black rat, Rattus rattus, and the brown rat, Rattus norvegicus...
do not depend upon visual cues like some of the other species tested. Its nocturnal habits lead it to seek food largely by smell. When moving about in the dark, it responds to tactual cues from its stiff whiskers (vibrissae) located on its snout. Hooded rats tested on the visual cliff show little preference for either side of the visual cliff apparatus as long as they could feel the glass with their vibrissae. When placed upon the glass over the deep side, they move about as if there was no cliff.
Cats/Kittens
Cats, like rats, are nocturnal animals, sensitive to tactual cues from their vibrissae. But the cat, as a predator, must rely more on its sight. Kittens proved to have excellent depth-discrimination. At four weeks, the earliest age that a kitten can skillfully move about, they preferred the shallow side of the cliff. When placed on the glass over the deep side, they either freeze or circle backward until they reach the shallow side of the cliff.Turtles
The animals that showed the poorest performance in the study were the turtlesTurtle
Turtles are reptiles of the order Testudines , characterised by a special bony or cartilaginous shell developed from their ribs that acts as a shield...
. The late Robert M. Yerkes of Harvard University found in 1904 that aquatic turtles have somewhat worse depth-discrimination than land turtles. On the visual cliff one might expect an aquatic turtle to respond to the reflections from the glass as it might to water and prefer the deep side for this reason. They showed no such preference, 76 percent of the aquatic turtles crawled onto the shallow side. The large percentage that choose the deep side suggests either that this turtle has worse depth-discrimination than other animals, or that its natural habitat gives it less occasions to "fear" a fall.
Cows
The ability for cows (Bos taurus)Cattle
Cattle are the most common type of large domesticated ungulates. They are a prominent modern member of the subfamily Bovinae, are the most widespread species of the genus Bos, and are most commonly classified collectively as Bos primigenius...
to perceive a visual cliff was tested by NA Arnold et al. Twelve dairy heifers were exposed to a visual cliff in the form of a milking pit while walking through a milking facility. Over this five day experiment the heifers’ heart rates were measured along with the number of times they stopped throughout the milking facility. Dairy heifers in the experimental group were exposed to a visual cliff while dairy heifers in the control group were not. The experimental group was found to have significantly higher heart rates and stop more frequently than the heifers in the control group. Depth exposure did not have any effect on cortisol levels or the ease of handling of the animals. These findings provide evidence of both depth perception and acute fear of heights in cows. This may lead to a reorganization of the way milking factories function.
Chicks
Two-day-old chicksChicken
The chicken is a domesticated fowl, a subspecies of the Red Junglefowl. As one of the most common and widespread domestic animals, and with a population of more than 24 billion in 2003, there are more chickens in the world than any other species of bird...
responded to the visual cliff when tested by PR Green et al. As the depth of the visual cliff below the chicks was increased the latency for the chick to move towards the incentive, another chick on the far side of the apparatus, was increased while the speed at which they moved decreased. On the other hand chicks that were given the same incentive to jump over a visible edge onto the deep side of the apparatus were less inclined to move at all depths. This illustrates that the absolute depth of a surface and the relative depth of an edge affect behavior differently in chicks.
Findings
Gibson and Walk discovered that all species tested can perceive and avoid a sharp drop by the time they take up independent locomotionAnimal locomotion
Animal locomotion, which is the act of self-propulsion by an animal, has many manifestations, including running, swimming, jumping and flying. Animals move for a variety of reasons, such as to find food, a mate, or a suitable microhabitat, and to escape predators...
. Most rely on visual cues for depth perception. The rat however, relies on olfactory and tactile cues (being nocturnal) but will fall back on vision when needed. Next, the experimenters wanted to find out which visual cues played a decisive role in depth perception. Using dark-reared animals, they concluded motion parallax is an innate cue for depth discrimination, whereas responses to differential pattern-density may be learned later.
See also
- Depth perceptionDepth perceptionDepth perception is the visual ability to perceive the world in three dimensions and the distance of an object. Depth sensation is the ability to move accurately, or to respond consistently, based on the distances of objects in an environment....
- Developmental psychologyDevelopmental psychologyDevelopmental psychology, also known as human development, is the scientific study of systematic psychological changes, emotional changes, and perception changes that occur in human beings over the course of their life span. Originally concerned with infants and children, the field has expanded to...
- Child Psychology
- PsychologyPsychologyPsychology is the study of the mind and behavior. Its immediate goal is to understand individuals and groups by both establishing general principles and researching specific cases. For many, the ultimate goal of psychology is to benefit society...