20C (Gibson & Walk: depth perception, 1987)

Background- sensory processing

infants are prone to falls

• as they grow- avoidance of accidents

• able to stand

• avoid edges and objects

is this learning innate or a result of experience?

what did Gibson and Walk want to examine specifically

depth perception

• how do infants develop depth perception

• at what stage of development can an animal respond to depth and distance

• does onset of these responses vary with animals or different species

the visual cliff

to investigate these question → created the visual cliff apparatus

• on a foot long plank of wood

• most commonly used for space perception

• allows for control of auditory and tactual stimuli

• protects participants (safe)- high in ecological validity but also safe

Experiment 1- participants

participants :

• 36 infants

• 6 months to 14 months

procedure

1. each child was placed on the centre board

2. mother calls them from the cliff side

3. mother calls infant to the shallow side

DV: does the child crawl?

findings

27/30 infants crawled to the shallow side

• Only 3 crept onto the glass on the cliff side

• Many infants crawled away from mother when she called to them on cliff side

  • Infants cried when mother stood on cliff side

Clear evidence of their dependence on vision

conclusion

 

Conclusion= most human infants can discriminate depth as soon as they can crawl

• Sense of security depends on visual cues

  • Infants would often peer down through the glass on the deep side and back away

• Others would pat the glass with their hands and still refuse to cross

 Perception of depth matured more rapidly than locomotor abilities

• However: does not prove that infants perception and avoidance of the cliff are innate

experimental replications

to test if it in innate:

visual cliff tested on:

• chicks, turtles, rats, lambs, pigs, kittens and dogs

• animals were placed on the centre

• tested the direction they moved

• goats and lambs placed on a surface that could be lowered ton create a visual cliff

further replications

adjustment of the depth of the deep side on visual cliff

• fixed patterned material to a sheet of plywood

• moved it up

• lower it moved → deeper it appeared

findings

optical floor dropped → animal freezes in a defensive posture

conclusion= sense of security continued to depend on visual cues fro perception of depth

exception → rats depended on smell and tactual cues from whiskers

• rats showed little preference to the shallow side

conclusions

 

Conclusions- Depth perception is dependent on visual cues

• These develop early in life (chicks:24hrs)

• Evolutionarily-wired

• Rats may be different because nocturnal- depend on other sensory information

further replications

Bias in testing?

• Gibson and Walk (1960) tested out different patterns

• Different animals

• Different depths

For all= concluded that depth perception is evolutionarily reared and independent of learning

→ may have been an interaction to the mothers emotional response and environment

extension

Perception of Affordances

• 1908s- Gibson reconceptualised her studies

• The idea of ‘affordances’= fit between an animal’s physical capabilities and the features of the environment allow a particular action to be performed (Gibson, 1988)- own size relative to the drop

reconceptualisation led to a series of further studies

differences between crawling and walking

within the perception of affordances studies:

Gibson → focussed on crawling vs walking and rigidity of surface

• Differences in stability of posture affect affordances of locomotion

• Rigidity of ground surface varied (waterbed etc)

findings:

• Crawling infants crossed a squishy waterbed more often than walking infants

• Both groups went over rigid plywood

support for the idea of fit between physical capabilities and environment (perception of affordances)

Debate and controversy- criticisms

• depth perception may be learnt due to interaction with their environment as they grow (crawling etc)

• small samples

• range of ages (may have learnt depth perception

  • but supported with animal studies

further ciriticims

• did not examine the underlying reasons fro moving away from the visual cliff (parent interaction or depth perception?

• glass on deep side= conflicting tactile information

• conducted ina lab → low ecological validity

Impact and legacy

social referencing

Gibson & Walk (1987)

• Noticed that human infants (only) seeked social information from mothers (e.g., held out their arms towards them, pointed to them, looked at them)

however: Gibson and Walk did not use visual cliff much in understanding infants’ use of social information in guiding action

 Future studies-

• use visual cliff as most famous paradigm for studying social referencing (Baldwin & Moses, 1996)

the future studies

examining maternal emotional signalling

Sorce, Emde, Campos & Klinnert (1985)

• Examined the role of expressions of emotion on infants’ visual cliff responses

 Participants:

• Infants of 9-12 months

procedure

happy vs fear

• used visual cliff with adjustment of depth

• infants placed on shallow side of cliff, mother on deep side of cliff

• mother placed toy on deep side and instructed to smile or fear face (no words, sounds or gestures)

• maternal facial expressions scored independently by naïve raters

findings

mothers happy or fear signalling influenced infants’ behaviour

• fearful expression → NONE of the infants went on the deep side (11 retreated)

• happy face- 14/19 infants crossed on the deep side (3/19 retreated)

more studies on this social referencing

replications manipulated:

sadness

• intermediate number crossed to deep side

absence of depth

• few infants reference mother

conclusion → facial expression regulate behaviour in contexts of uncertainty

is this 100% replicable

nope, some conflicting evidence

Bradshaw et al (1987)

• failed to replicate findings of mothers facial expression

• did find an effect for speaking to infants AND having happy facial expression