Gibson and Walk Flashcards
What awards did Gibson get?
- 1968: Award from the American Psychological Association (APA)
- 1992: National Medal of Science
What were the devlopment of the visual cliff
The Grand Canyon Story
The Goats Story
The Dark-Reared Rats Story
what did Lashley and Ruddsel find about rats?
- Light- and dark-reared rats jumped variable distance
- Concluded that depth perception is innate
- But some pre-training required
- There is some innate ability but to some extent environment and learning is important
what did Gibson and Walk find about eliminating pre-training
- Visual cliff has a centre piece- on side is shallow and the other deeper
- The rat would be placed in the centre to see which side they preferred
- Both light- and dark-reared rats preferred the ‘shallow’ side (very few dropped down onto the ‘deep’ side)
- Suggests an innate ability to detect death
What was Gibson and Wak’s procedure
Participants- 36 infants (6-14 months)
Procedure- Place infant on centre board, Mother tries to attract infant to cross either deep or shallow side
what did Gibson and Walk find
Results- All 27 infants who moved off the board did so on the shallow side
Only 3 crept over the deep side
Many crawled away or cried when mother was on the deep side
Conclusion- Human infants can discriminate depth as soon as they can crawl (But is it innate?)
How did Chicks react to the visual clifff
- Tested <24 hours old never crossed the deep end
* Chicks must scratch for food immediately
how did lambs and goats react to the visual cliff
• Able to walk immediately (escape from predators)
• Experiment: Never crossed the deep end
• Stereotypical response to being placed on the deep side
• Adjustable drop (~ 1 foot = critical)
Even with experience of walking on the glass visual cues were always critical to their sense of danger
Stereotypical responses: trembling, stretching/stiff front legs
how did rats react to the visual cliff
- Rely more on tactile cues from whiskers
- Hooded rats show little preference for the shallow side as long as they can use their whiskers to feel the glass
- Move normally when placed on the glass on the deep side
- When the centre board is raised so they can’t use their whiskers 95-100% moved down on the shallow side
how did kittens react to the visual cliff
- Nocturnal (use whiskers)
- Predators who rely on vision to hunt
- At 4 weeks (when they can move around confidently) they always choose the shallow side
- When placed on the glass on the deep side they freeze or circle back to the centre board
how did turtles react to the visual cliff
- Aquatic turtles have worse depth perception than land turtles
- You might expect the reflectivity of the glass to attract aquatics
- 76% chose the shallow side
- Worse depth perception or less fear of falling?
What are the two deciding factors
Relative size of pattern or ‘motion parallax’
what is the parallax deciding factor
Increased size and spacing of pattern on deep side to match shallow side (and thus reduce relative size of pattern as cue)
Results
• Adult rats preferred the shallow side (but not as much as before)
• Infant rats and chicks chose the shallow side almost exclusively
Relative size of pattern or ‘motion parallax’?
what is the pattern size only deciding factor
• Pattern directly under glass on both sides (to eliminate motion parallax as cue)
• Smaller, more tightly spaced pattern on ‘cliff’ side
Result
• Young and old hooded rats preferred the big pattern (suggesting a shallow side)
• 1-day old chicks showed no preference
Learned environmental cues?
what is the pattern only results in animals
Dark-reared rats
• Motion parallax only: preferred shallow side
• Size/density only: no preference
Dark-reared kittens • Blind when exposed to light • No preference on day 1, by 1 week responding like light-reared kittens • Did not learn that the glass is safe • Suggests innatism
what was the conclusion abotu only pattern size being the deciding factor
Conclusion
• Only motion parallax is innate
• Pattern density is learned
What are the hidden biases
- reflection from glass
- patterned surface
- other optical illusions
- covering the deep side with glass
- measuring responses with just yes/no
- locomotor experience
how is covering the deep side with glass a bias?
• Conflicting visual and tactile information
• Babies who have played with transparent boxes at home do not avoid the deep side (Titzer, 1995)
• Learning has an impact
Humans learn that the glass is safe (e.g., Walk, 1966)
• With a ‘catcher’ they never do (e.g., Adolph, 1997)
• Need to be exposed to learn
• Without the glass infants explore the edge of the cliff:
• Stretching arms down or across the gap
• Judging the distance relative to their size
• Observing and making a judgement call
• Backing down feet first
• Sliding down on their bum
• Glass interferes with research of such strategies
What is locomotor experience
• Age of crawling onset better predictor than days of experience (e.g., Rader, Bausano & Richards, 1980)
• Pre-crawlers rolled over the edge (e.g. Rader et al., 1980)
• BUT: Crawling experience better predictor than crawling onset age (e.g., Bertenthal & Campos, 1987)
Inconclusive evidence regarding experience vs maturity
What have we learned from the visual cliff
- depth perception
- perception of affodances
- fear of heights
- social referencing
What did Gibson et al comment
• Interacting with the environment (Gibson et al., 1987) creates a growing knowledge of affordances
– Surface stability – waterbed v solid ply
– Experience is specific to each posture (sitting, crawling, walking)
What did witherington find about fear of heights
• Visual cliff does not induce ‘fear’ but exploration
what did source find about social referencing
• With ambiguous drop-off (30 cm) 12-month-olds only cross with neutral/happy but not with angry/fear faces
