Gibson and Walk

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What is depth perception?	Depth perception is interpreting how far an object is spatially and is important for staying safe within our environments as we wouldn't survive very long without it e.g. descending stairs could kill us
Why did Gibson and Walk want to investigate depth perception?	The nativists, empiricists and interactionists all have different beliefs as to how we become aware of our surroundings
What do nativists believe about depth perception? Give an example to elaborate...	The nativists believe that depth perception is an innate ability and this ability may not be present at birth and it's maturation rather than learning that determines the development of these capacities. For example, when a child is born, their nervous system has the necessary components to perceive depth but is immature - the optic nerve is shorter than adult sized and narrower and doesn't have the myelin sheath to ensure good transmission of information
What do the empiricists believe about depth perception?	Empiricists believe we acquire abilities through experience and that depth perception would be acquired in response to environmental demands i.e after we become independently mobile
What do interactionists believe about depth perception? Give an example...	Interactionists believe that our abilities are a result of innate factors and environmental factors interacting. They would assume that depth perception is due to the visual system developing (the myelin sheath around the optic nerve is thought to be fully developed around 4 months) combined with experience (e.g. being exposed to various complex stimuli such as faces give some indications of depth).
Why would we expect depth perception to be apparent when the infant is mobile?	We would expect depth perception to be apparent when the infant is mobile (6 months in humans, earlier in precocial animals) if DP is innate as this is adaptive behaviour (increases survival rate)
What did G+W want to investigate?	G+W wanted to investigate whether a human infant could discriminate depth by the time they were independently mobile and whether it was due to learning through experience or what the child is born with (innate)
If perception is innate, when would we expect it to be apparent by?	If perception is innate it should be apparent by the time they're mobile
Why did they use a range of non-human animals?	To investigate whether depth perception (cliff avoidance behaviors) was evident when the animals were mobile
Where was the study conducted and what was it called?	At Cornell University in the USA, G+W carried out a lab experiment called the "The Visual Cliff" to investigate depth perception in babies and other young animals.
What did the apparatus allow G+W to do?	The apparatus enabled G+W to control optical,auditory and tactile stimulus and to also protect participants (ppts).
Describe the "visual cliff"	The visual cliff consisted of a large glass sheet supported 30cm above the floor, on one side a sheet of patterned material was placed directly beneath the glass while on the other side the patterned material was laid on the floor (this side of the apparatus formed the visual cliff) - the patterns on the material underneath the glass gave visual cues that one side was "shallow" and the other was "deep"
What did they do to the ppts in reference to the "visual cliff"?	The ppts were placed on the centre board that lay between the shallow and deep sides and then were encoraged to move across the shallow and deep sides in order to observe whether they would refuse to crawl over the drop
How many humans ppts and how old were they?	36 human infants aged 6-14 months who could crawl participated
Which animals participated?	The animals that participated: chicks, lambs, kids (all mobile at 1 day old); kitten (mobile at 4 weeks old); kittens reared in the dark for 27 days (had no perceptual experience before they became mobile); rats( mobile at 4 weeks old); rats reared in the dark; rats that wore hoods so they could use whiskers rather than visual cues; aquatic turtles, dogs and cats
Why did aquatic turtles participate?	Their depth perception may be different to land based animals as their normal environment is partially underwater
Why were control experiments conducted?	Control experiments were conducted to eliminate possible confounding variables - e.g it's possible that reflections from the glass affected ppt's behaviors so they lit the patterned surfaces from below the glass
What was done to remove depth cue of motion parallax?	To remove depth cue of motion parallax, the patterned material was placed directly beneath the glass on both sides, but the pattern size was adjusted so that the squares on the "shallow" sides were bigger, giving the illusion of being closer
How many infants attempted to crawl onto the deep side and what conclusion was drawn from this?	Of the 27 infants that moved, only 3 attempted to crawl into the deep side, all were happy to crawl onto the shallow side. The conclusion drawn from this was that infants are able to detect difference in depth as they preferred the shallow side but this doesn't prove the nativist's view as they could've learned this after birth.
Why did the infants cry and what did this show?	Many infants crawled away from the mother when called from the deep side while others cried as they couldn't get there without crossing the deep sides - this showed that the infants wanted to get to their mothers (got upset) but only a minority were willing to defy eyes and cross the cliff
What happened with the chicks, kids and lambs. What conclusions were drawn from this?	Chicks, kids and lambs never hopped or stepped onto the deep side (even at 1 day old) and kids/lambs placed on the deep side froze in a defense posture. G+W concluded that from the moment they're born, they can detect depth (as they're afraid of it) and this supports the nativist's view that depth perception is innate
What were the results with the rats and what did G+W conclude about this?	The rats were content to explore both sides (could feel glass with whiskers) and when the center board was placed higher where the glass was out of reach, rats only wend to the shallow side. G+W concluded that species which use a different way of perceiving depth/environment use visual cues when other cues are removed.
How do the findings for the rats support the empiricists view?	The findings for the rats supports the empiricist's view as when shape/size cues are available, they were learning. This is further supported by dark reared rats which had no preference to which side they went as they hadn't learnt from their environment about perception.
What did the research with rats suggest about motion parallax?	The research with rats suggests that motion parallax is an innate cue, whereas size/spacing is a learned cue.
What were the results with the aquatic turtles and what did G+W conclude about this?	76% of the aquatic turtles crawled off onto the shallow side - the large minority that chose the deep side suggests that the turtle has poorer depth discrimination than other animals - G+W suggest that its natural habitat doesn't really pose it with the "occasion to fall"
Why is a lab experiment an advantage in this study?	A lab based experiment was used which means confounding variables (such as distractions to the child) can be controlled which means causal relationships can be established.
What is a disadvantage of the method that lowers internal validity?	However a disadvantage of the method that lowers internal validity is that there are problems interpreting the behaviour of the infant however it could be argued that the results for the deep side are fairly conclusive so depth perception is what the method is measuring.
How is internal validity increased by the behaviour we see due to the method?	Babies (human/animal) wouldn't realize the demand characteristics or aims of the study so we can assume that the behaviour we see is truthful increasing internal validity.
How is there high replicability?	The method also has high replicability because the apparatus is easy to assemble which increases reliability.
How do the infants ages affect reliability?	However reliability is reduced by the fact that the infant’s ages were inconsistent (varied between 6 -14 months) – this is bad because in the 14 month child, depth perception may have been learned and therefore might not be innate.
How does the sample composition affect external validity?	External validity is also lowered because the sample was ethnocentric as they were all from the US(culture may influence child-rearing and possibly development of depth perception), animals were used (with different biological systems) and a small sample size was used and therefore the results can’t be generalized and so population validity is low.
Why is there low ecological validity?	There’s low ecological validity too as mundane realism is low (in reality a mum would never egg her child to cross something that the child could potentially fall down and hurt themselves on).
How did psychological harm affect the infants?	There’s also ethical issues as psychological harm of distress is caused to the child (some babies started crying when they’re mums were encouraging them over the deep side but they realized it was dangerous). Also the lambs and the kids froze in fear when they were placed on the deep side
What are the ethical issues behind the kittens reared in the dark?	The kittens were also reared in the dark – it’s cruel to do this to an animal just for the sake of an experiment especially when this affected their depth perception ability but they were kept in normal lighting conditions and had the same response as normal kittens so there were no lasting effects.
What was Schwartz (1973) et al's findings?	placed 5 - 9 month old infants on deep/shallow side, measured heart rate when placed over drop, 5 month old: no increase in heart rate, 9 month old did
How do Schwartz (1973) et al's findings support G+W?	Those in same age group in G+W's study (who were mobile) showed physical changes and those who weren't mobile didn't (younger babies showed no difference in heart rate). This suggests that an innate ability of depth perception may not be present however, those with no increased heart rate may have depth awareness but no fear response to gap as their survival ability is questionable. But by 9 months the infants could have learned depth perception so it may not be innate.
What did Sorce (1985) find?	performed variation in visual cliff expt, mother had to maintain expression of fear or happiness on other side of 'cliff' when mother smiled = babies crossed cliff when mother expressed fear = babies more reluctant to cross
How do Sorce's (1985) findings develop G+W's exp?	Depth perception may be innate but infants still learn through environment/upbringing depth response as their ability to judge is present but reaction learnt – interactionist explanation not just empiricist or nativist. Also this study has more mundane realism as a mother is likely to express fear if her child was in danger of falling down something.
What did Bower et al (1970) find?	 infants of 6 days shown 2 objects large disc approach to within 20cm of them small disc approached to within 8cm of them  both objects created retinal image of same size suggesting equal distances infants so upset by smaller closer disc, study stopped early
How did Bower et al's (1970) findings contradict G+W's findings?	Suggests depth perception may be innate but may occur earlier than G+W claim (before crawling) and suggests in species which are not prococial, depth perception could occur. Also a limitation of G+W's study is that by 6 months the infants could have learned depth perception so it becomes difficult to untangle innate and environmental factors which may have affected depth perception but Bower et al's findings for younger babies who've had much less time to learn depth perception is inconsistent with G+W's findings contradicting it.
What did Bremner(1994) conclude and how does this develop G+W's findings?	concluded that the ability to interpret dynamic visual info (movement) occurs earlier than static visual info about depth possibly DEVELOPS as links to ability shown by Bower and that perhaps depth perception involves different processes that must be broken down further e.g vertical, horizontal, distance perception, or movement, static, object perception etc providing possible areas of further research

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