Perceptual development

•Nativists believe we are born with certain innate abilities. Some may be incomplete or immature but they will develop because we are genetically programmed for this. Abilities are not learnt. •E.G. walking –we are programmed to walk upright, unless we have a physical disability, we will do so without any training as soon as muscles and skeleton mature enough. –We are not ‘hard-wired’ to fly, no matter how much maturation or trying takes place!

•Empiricists believe a child develops abilities through experience with the environment. •The environment could be: –Personal experiences –Personal circumstances –Social context –Cultural context etc

•How could we find out? •Infant / neonate (newborns) studies. •The suggestion is that if abilities are innate, they should be present in a newborn, if they are learnt, then these abilities wont be present.

•BUT ….. How can you tell? –Especially when babies can’t talk to you …. or they fall asleep. –Is it ethical to experiment on babies? –Maybe the innate ability takes a while to show (maturation). Just because it’s not there doesn’t mean it isn’t innate.

•Animal studies –Gets round the ethics problem (except for Lei), can put them into deprived environments and see what happens •Case Studies –People who have been blind since birth then have surgery to restore their sight. Usually adults so they can talk! •Human distortion studies –Adult volunteers who try out equipment that distorts their visual world and see if they can adapt. •Cross-cultural studies –Are perceptual abilities universal? If innate they should be

•The perceptual constancies –Depth (look at some of the cues we use) –Visual constancies (size, shape, colour) •But …. How much can babies see? –Visual acuity = how much visual detail you can see. –Newborns about the same as an adult cat i.e. can’t see detail very far away. –Develops quickly and same as adult by about a year old

The visual cliff was developed to investigate the process of depth perception, or seeing objects in three dimensions. E.J. Gibson and Richard Walk (1960) studied infant’s depth perception by using a small cliff with a drop-off covered by glass. Gibson and Walk would then place 6-14 month old infants on the edge of the visual cliff to see if they would crawl “over the edge”. Most infants refused to crawl out on the glass signifying that they could perceive depth and that depth perception is not learned ^[1].

The "Visual Cliff" was a wooden table from the edge of which strong plate glass extended, Life magazine reported in 1959. Children were put on the table top and coaxed to crawl out over the glass, the magazine said. But when they got to the edge of the cliff and looked down almost all of them quickly withdrew. Even their mothers' most persuasive urgings could not get them out. Similar studies were done with animals, including rats and kittens.

The findings indicated that perception is an essentially adaptive process, or as Dr. Gibson put it, We perceive to learn, as well as learn to perceive.