<P> The ability for cows 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 . </P> <P> Two - day - old chicks 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 . </P> <P> Lambs are able to stand and learn to walk almost as soon as they are born . Just like chicks, they were able to be tested as soon as they could stand . They did not make one error when tested on the visual cliff . When placed on the deep side of the glass, they would become scared and they would tense up and be afraid to move . However, when they were moved to the shallow side they would relax and jump onto the visually shallow surface . This showed that visual sense, instead of the ability of the animal to feel the stableness of the glass, was in control . </P> <P> One of the criticisms of the visual cliff study was, "Did they really support the hypothesis that depth perception was innate in humans?" One issue was about the glass over the deep part of the visual cliff . By covering up the deep side with glass the researchers enabled the babies to feel the solidity of the glass before they would cross over . This response was repeated over and over again in tests . Another criticism has to do with the experience of the infant . Infants who learned to crawl before 6.5 months of age had crossed the glass, but the ones that learned to crawl after 6.5 months of age avoided crossing the glass . This helps support the hypothesis that experience does influence avoidance of the glass, rather than just being innate . </P>

What conclusion can you draw from the visual cliff experiment about depth perception