GIBSON AND WALK (1960)The Visual Cliff

CONTEXT Nativist view- innate ability to perceive the

world. Opposed to learning through experience.

Lashley and Russell (1934)- rats reared in dark could still jump correct distance to platform. Criticism: Invalid- rats could have learnt to judge

distance through training.

AIM Investigate whether depth perception is

innate or learned. Will mobile infants avoid a visual drop?

PROCEDURE: SAMPLE 36 human infants aged 6-14 months and

their mothers. Must be mobile- able to crawl.

Followed by trials with animal young, e.g chicks, kids, lambs, rats, puppies and kittens.

Another trial used only kids (goats) and lambs because they could be tested within 24 hrs of birth. No opportunity to learn to perceive depth.

PROCEDURE: EQUIPMENT The Visual Cliff

Surface usually in a check pattern (to show clear depth cues) and a drop covered by a glass floor. The glass floor controls for other non-visual cues.

PROCEDURE- METHOD Child is placed in centre of visual cliff. Mother beckons child towards her from both

sides (shallow and visual cliff) to test if the infant is less inclined to cross a visual cliff.

Animal trials were used to reduce the chance of pre-crawl learning. Animals were placed in the centre and the

direction in which they moved was tested (towards or away from the visual cliff)

Kids and lambs were then placed on a surface, which could be lowered to create a visual cliff, to test their response to visual cues suggesting the floor was moving further away.

PROCEDURE- METHOD CONT. In another condition the

check surface was replaced by a uniformly grey one to ensure the validity of the measure. Was it the depth cues, which

are eliminated by the grey surface, causing the participant’s reactions?

RESULTS 27/32 infants moved off the centreboard.

All 27 crawled onto the shallow surface. Only 3 ventured on to the visual cliff. Many infants moved away from their mother if

she was beckoning them towards the visual cliff.

RESULTS CONT. No lambs, kids or chicks ventured onto the

visual cliff. When placed on the visual cliff they froze.

In the adjustable cliff condition all animals froze when the visual cliff dropped more that 12 inches. They did not adapt after multiple trials.

In the uniform grey condition animals showed no preference for either side of the surface.

CONCLUSIONS All animals, including humans, had intact

depth perception by the time they could move.

In animals this occured within 24hrs of birth, suggesting depth perception is innate.

Thus, the nativist position is supported. The grey condition showed the innate

mechanism for depth perception involves interpreting changes in patterns.

EVALUATION- STRENGTHS The visual cliff is a safe and easily

identifiable measure. Visual cliff procedure controlled for

extraneous variables, such as touch perception. Improved validity.

Tested on a range of species. Straightforward procedure.

Easily replicable- good external reliability. Participants all had a very similar experience-

good internal validity.

EVALUATION- WEAKNESSES Small sample. Large age range of infants. Infants have time

to learn depth perception. Conclusions are justified by trials with other

species. Behavioural measure- could not test infant’s

or animal’s reasons for moving away from the visual cliff. Issue of validity.

Ethics- causing distress to infants and animals. Cannot be asked for consent directly. Unable to withdraw.

ALTERNATIVE EVIDENCE- SUPPORTING Tondel and Candy (2007)

Method: Presented infants aged 5-7mnths with image of fast-moving clown.

Conclusion: Infants were able to track clown even at speeds of 50cm/sec. Visual tracking is innate.

Sinai, Ooi, and Hi (1998) Method: Adults ability to judge distance up to

7m. Conclusion: When the ground was even, texture

was used as a cue, and judgements of distance were more accurate. When the pattern was obscured, e.g. By a ditch, accuracy declined. Supports that pattern is an important depth cue, as in Gibson and Walk’s grey condition.

ALTERNATE EVIDENCE- OPPOSING Pei, Pettet, and Norcia (2007)

Whilst some basic perceptual processes are innate, they develop through experience.

Carried out experiments using a range of patterns and shapes, demonstrating that infants could not recognise the more subtle differences in texture that adults can.