key study : gibson and walk

aim

• investigating age at which infants and young animals perceive depth

• support that depth perception is innate

• role of creative size and motion parallax in depth perception

research method and design

• for human infants :

• lab experiment

• repeated measures design

• for animals :

• quasi experiment

variables

• child IV : if the infant was called from the cliff side or the shallow side

• child DV : whether or not the child crawled

• animal IV : type of animal

• animal DV : preference to side (deep or shallow)

sample

• 36 human infants ranging from 6 months to 14 months and their mother who gave consent

• unspecified number of young animals

• animals were : chicks, turtles, rats, lambs, baby goats, pigs, kittens and puppies

procedure

• table with glass over the top, one side a checked print right underneath the glass (shallow side), on the other side a checkered pattern on the floor (deep side)

• was a ‘border’ around the table for safety

• each child was placed on the centre of the board, and their mother called them from the cliff side and the shallow side successively

• similarly the animals were placed on the visual cliff and their behaviour was observed

human trial results

• all infants that left the centre board crawled onto the shallow side at least once

• only 3 babies crept onto the deep side

• some infants patted the glass but still refused to go onto the deep side

animal trials results

• like babies, young animals places on the visual cliff moved to the shallow side

• there were differences in age at which depth perception developed

• depth perception emerges once an animal becomes mobile

• kittens : at 4 weeks (earliest kittens can move around) they chose shallow side, if put on deep side they froze and tried to move back

• turtles : were the worst, 76% of turtles crawled off the board to deep side

• rats : moves over both sides as long as their whiskers were touching the glass

control trials and results

• conducted (using rats) to ensure design of the visual cliff had no hidden bias

• included changes to lighting, patterns and height distance for each side

• observed the impact of each change

• was no hidden bias influencing choice

• when tested using surface lit from below to eliminate reflections, rats consistently chose shallow side (was a valid measure of depth perception)

• when patterned surface was replaced with a grey surface, they showed no preference for either side, as no depth clues

human trial conclusions

• most infants can discriminate depth when they can crawl

• depth perception in humans develops before other abilities e.g. walking

animal trials conclusions

• an animal can discriminate depth when it can move

• depth perception in chicks, kids and kittens develop rapidly

• depth perception in rats is innate

• depth perception in kittens is maturational

general conclusion

• survival of any species requires that it members develop depth discrimination by the time they take up motion in order to avoid dangers and navigate their environment effectively

validity

• low ecological as it was an artificial environment (visual cliff) but this was to ensure it was ethical

• high internal as genuine responses are shown (e.g. when placed on deep side kittens froze indicating a true fear response)

reliability

• generally high reliability as standardised procedures used e.g. same visual cliff apparatus used throughout

• however reliability is lowered as mothers may have called their babies in different ways (more or less enthusiasm) and how attached each baby was to it mother was not standardised

sample and generalisation

• relatively small samples

• however many different species of animals used so more generalisable across the species that were studied

research method

• the human trials were lab experiments with a repeated measures design

• means they were highly standardised and high levels of control but due to it being repeated measures is potential for fatigue effects

• animal trials were quasi lab experiments as the IV was naturally occurring which makes it more generalisable

practical applications

• if we know when a child’s depth perception should develop, we are able to tell when it may not have developed properly and provide help

• e.g. using SI therapy or wearing glasses

type of data

• both types of data collected

• qualitative data as observations of behaviour recorded

• quantitative data as analysed quantitatively and numbers of each baby species that moved recorded

freewill vs determinism

• biologically deterministic as depth perception is innate

• humans and animals develop depth perception at different times

nature vs nurture

• supports nature as argues depth perception is innate (ppts are so young its presumed to be biological and not environmental)

• however depth perception changes and babies are capable of seeing light suggesting environmental influences (nurture)

ethics

• slightly unethical as visual cliff could be distressing for babies (not protected from harm)

• also can’t get informed consent for the animal trials

usefulness

• is useful as highlights when depth perception should develop and so can be used to identify abnormalities

• provides insights into visual development, aiding in understanding and diagnosing perceptual disorders.

reductionism vs holism

• overall holistic as suggests that depth perception is due to many factors

• both biological and environmental

socially sensitive research

• not socially sensitive

• does not create any harmful stereotypes

psych as a science

• lab experiment so high level of control - is therefore objective and standardised

• reduced effect of extraneous variables by doing control trials - reducing light reflection