Week 4: Sensation & Perception Flashcards
What was John Locke’s view on newborns?
Thought they were born with the mind like a white page. All ideas and abilities developed through learning and experiences of the world
Nothing -> things develop
What did William James suggest about newborns?
That babies can’t distinguish between sensations ‘one great blooming, buzzing confusion’
What is today’s view on infants?
They are born with many skills, and actively learn many more rapidly as they explore the world.
What is sensation?
The detection and discrimination of sensory information from sensory organs
What is perception?
Interpretation of those sensations, including recognition and identification
What is the most important sense?
Vision - takes up nearly half of the cerebral cortex (massively over represented in the brain)
Vision in newborn babies?
Infants are born with well developed vision which improves rapidly
Popular vision testing methods?
Preferential looking tasks
Habituation
Conditioned head turn (also used for hearing)
What is a preferential looking task?
Measure looking time between two similar visual stimuli
If they look at one for longer, they have a preference for it
If equal - can’t discriminate or they find both equally interesting
What is habituation?
A gradual decrease in response to/interest in a repeated stimulus
Why is habituation useful?
Means you won’t continuously notice things that are there all of the time
Allows us to be alerted to things that we may need to pay attention to (self-preservation)
What is novelty preference?
Human preference for anything new or different
Habituation experimental design for visual assessment?
Present infant with stimuli: attention/interest
Keep on presenting it: declines
Infant = habituated
Present a different stimuli - if attention increases, assume they can distinguish between the two
Visual acuity at birth?
Infants can see (20-25cm), but lack visual acuity
When is an infants visual acuity comparable to adults?
About 6 months
How do we test visual acuity in infants?
Preferential looking: narrow stripes over plain field
Change the width of stripes, infants prefer the stripes as they are more interesting. When they don’t have a preference it means they don’t perceive the stripes anymore and it looks more like a plain field to them.
Colour vision in infants?
Initially very limited - begins to develop as cones mature.
By 2-3m start to perceive adult like colour categories
By 4-5m have colour preferences
Pattern vision?
As infants get older, they prefer complex patterns
Infants look longer at a patterned surface more than a plain surface.
What do edges and contrasts provide?
Information on object boundaries
Depth and how to grasp objects
Greater neural activation - developing neural pathways of pattern recognition
Children prefer looking at faces over pattered displays. Explain.
May be genetically preprogrammed to prefer faces (eg. Attached to adults who will look after you)
They are 3D, move and have areas of high and low contrast
How does social learning affect face preference?
Infants prefer faces of those the same sex as their caregiver
Have a preference for faces matching those of their own race - more familiar
By 3 months, infants prefer sailing faces over non-smiling
What is the still face paradigm?
Three minutes with an expressionless mother the baby initially attempts to interact with the mother and then this face to the baby being sober and wary and don’t know how to deal with it eventually the baby becomes withdrawn and hopeless
After this normal interaction restores joy and normality
What broader implications does the still face paradigm have
Babies of mothers with depression so what happens if it’s chronic
Explain object constancy
Perception or belief that an object remains constant despite changes in the way that it looks
Why is object constancy important
Helps to maintain a stable perceptual world and you don’t have to constantly try and figure out the world
Conditioning studies suggest that infants have innate object constancy of what type
Shape and size constancy
Explain the conditioned head turned Paradigm
rewarded for turning their head to one side towards something
Then rewarded for only turning their head towards particular stimulus
If a child can consistently recognise that stimulus they should turn their head only to that one in particular
child begins to turn the head in anticipation when stimulus but not alternative is shown
What is evidence that object constancy develops relatively early in children
The conditioned head turn paradigm
Explain a study of object continuity
Four month old habituated to a rod behind a block
Preferential looking choice of a whole or a broken rod they prefer to look at the broken rod which was novel this suggests they had seen initial bits of the rod as part of a whole
How long does it take for infants to gain depth perception
It takes time to gain depth perception or to get it right and that’s okay because they’re not running around for a lot of this time
Explain the visual cliff experiment
There is a chequered surface with a drop-down or cliff with a sheet of glass on top so the babies are safe
Infant should be unwilling to cross the cliff if they can perceive depth
Two-month-old are simply curious where are 6 to 14 month old won’t crossed despite coaxing from parents.
How are infant heart rate changes similar to adults
Will decelerate in response to novel/attractive stimuli, and interesting but not exciting
Will accelerate in response to potentially dangerous or aversive stimuli or something very stimulating
How else can we perceive depth?
Kinetic cues (1-3m)
Binocular depth cues (4-6m)
Pictorial distance cues (5-7m)
Explain kinetic cues
They are produces as a person or object moves
- motion parallax: closer objects move faster, further objects move slower
- interposition: closer objects obscure further objects
- shadows: cast by closer objects on further objects
What are binocular depth cues?
Inter-eye disparity greater for closer objects than further objects
What are pictorial distance cues?
- linear perspective: two lines in parallel tend to appear to converge in the distance
- texture gradient
How can we test auditory perception
Can use habituation with: turning head or eyes to the sound, changing heart rate, change in breathing or sucking rate
Explain high amplitude sucking experiments
Dummy wired to the computer to get a baseline sucking rate
Sound played - initially sucking rate increases
Sucking/interest gradually declines as habituation occurs
Then change sound
If increased sucking = discrimination
At what age can a foetus respond to sounds?
As early as 24 weeks in utero
Eg. Prefer native language
How do we know infants can hear at birth?
They respond with startle reflexes, fists and crying
By 3 days of age, infants can…
Orient to the direction of sound
Can distinguish: 2-3 syllable words, happy-negative speech, ascending vs. descending sounds
Which part of auditory sensation continues to develop until age 10?
Pitch discrimination
At what age can infants locate sounds?
2 months
Smell and taste development?
Well developed in the last few months in utero, highly developed at birth
Food taste preferences?
Change with age
Foetus prefer sweeter
By 4 months, they start preferring salty over sweet
Touch in infants?
Foetus can respond as early as 8 weeks
What is touch sensitivity important for?
Exploring the environment (knowing how to hold things)
Positive emotional development (hugs)
Haptic perception?
The use of touch to explore objects (because vision is still developing)
Oral manipulation is most informative
Manual manipulation is also used
4-6 months: manual exploration tailored to object
3 years: adult like exploration
How do infants respond to pain?
Distress.
Facial expressions, crying, blood cortisol elevation
What else influences infants pain?
Others reactions and the environment
It is hard to assess older children’s experience of pain. How can you do it?
The faces pain scale
‘Point to the one that represents how much it hurts’
Intermodal perception?
Infants must be able to combine input from different senses to form a perception of events or objects this is crucial for understanding the world and informing behaviour
Explain one of the early Studies of intermodal perception
Tested one month old‘s ability to integrate visual and tactile information
Infants sucked on a smooth dummy or a bumpy dummy and then shown a visual display of both
Preferential looking displayed them looking longer at which dummy they thought they had sucked
For example if they sucked a bumpy dummy they would look at it longer because I preferred it and it was more familiar to them
This suggests that intermodal perception is an innate skill that improves with experience
