Perceptual development

Question 1

How do we study perception in development? + methods

Answer 1

In an ideal world, you will want to take children and raise them in very carefully controlled visual environments and then come back when they’re an adult and see whats happened to them (however this isn’t ethical)

You can do neural studies with animals and babies.

Methods that can be used

• EEG (put electrodes on scalp and look for changes in electrical activity)
• ethneres (shining as light on the scalp and looks for changes around the scalp)
• looking time

Question 2

How can you tell what a baby sees and thinks?
video

Answer 2

Mum waving glass of wine and baby is tracking it

One way to get an insight into how babies see and look at the world is to see what they look at

Question 3

Preferential looking- cats

Answer 3

Show baby 2 stimuli that are different to each other and present multiple trials and count up how long they stare at one thing to another. If they discriminate the cat from the dog, they might have a preference for cats for example.

Question 4

Video of baby preferentially looking + what is preferential looking

Answer 4

You can tell the baby is actively looking at things and you can code how long they look at things to build an idea about what things they can and cannot see/ what they can tell apart/ what visual preferences they have.

What does preferential looking do? Tells you whether or not a baby can tell 2 things apart.

You can look at looking behaviour in other ways- eg.

Violations of expectation paradigm (present a surprising event and time how long they take to look)

Question 5

In perception, what is one of the methods used?

Answer 5

Habituation paradigm

Question 6

How do you use the habituation paradigm?
What do you expect to see with cats and dogs?

Answer 6

In the habituation paradigm, you will familiarise a baby to a particular set of stimuli and then you have a test phase. This involves a novel example of something they’ve just seen lots of and then you have a completely novel stimulus that is from a different category.

What you expect if babies have a different category of cat and dog is that they will look for longer and the double novel thing.

Because they have been habituised/ familiarised with cats, they will look for longer at the novel category.

This can be done with any stimulus eg. colours or faces

Gives us a more concrete idea of whether infants think they’re conceptually different or the same.

Question 7

Example of Frantz’ set up

Answer 7

Infant looking preferences are reliable, and can reveal biases in the infant visual system such as the bias to high contrast images and specific stimuli.

Baby wheels in on trolley and experimenter can peep through hole

Frantz showed there were many types of stimuli including:
- complexity
- straight lines
- realistic face compared to schematic face

You find that infant looking time on average is very predictable.

Teller acuity charts- Infants would rather look at something rather than nothing. Theres a tiny hole and experimenters have to guess what side of the panel infants are looking at. If they can guess accurately what side they’re looking at, then they will show a version of this which is harder for the infants to see.

Question 8

What are sorts of preferences that infants have?

Answer 8

For an inverted triangle compared to a normal triangle:

They will look for longer at the inverted dot triangle

For normal face vs scrambled face:

They will look longer at the face that is correct in its configuration

Even thought both stimuli have the same features, the layout seems to have a big difference into what infants will look at.

Question 9

Reid et al, 2017- looked at what happened before infants are even born

What was done and found?

Answer 9

Used 3D ultrasound and shone a bright light to the uterine wall in pregnant people.

They were either in this inverted triangle or uprighted triangle layout

Infants will make more head turns to the inverted triangle.

This was before they had any visual experience at all and they already have this bias

This lets us know that there is something in the visual system that is bias to seeping out particular stimuli

Question 10

Taking adult- like perception for granted
List types of Visual Acuity

Answer 10

• Colour
• Depth
• Size
• Shape
• Orientation
• Segmentation
• Transparency
• Opaqueness
• Motion
• Constancy
• Sound
• Odour
• Etc…

Train to London example- adult visual system is able to tell what objects and things in the environment are.

Quite often when we talk about infant perception, blooming buzzing confusion phrase comes up. This is the idea that infants perception of the world, all things are still tuning in.

These things aren’t in place in infancy

Question 11

What is visual acuity?
When talking about visual acuity, what is said?

Answer 11

The level of detail that you can see as well as the amount of contrast

When talking about visual acuity, we often talk about contrast sensitivity function

Question 12

Visual Acuity:
- what is visual acuity poor at?

Answer 12

Visual acuity is poor at birth, but by 36 months (3 yrs) old children have 20/20 vision

Although acuity is poor, the general pattern for CSF is very similar to adults

Question 13

Visual Acuity:
Contrast sensitivity function graph
Comparing between children and adults

Answer 13

Red line shows the edge of your adult perception

In top right corner there is information that is very fine detail and very low contrast but your visual system can’t resolve it so it is effectively invisible to you.

Under this red curve you are able to discriminate. Its always this shape

For infants (right hand graph) you have the different contrast sensitivity functions for different aged children. (imagine lines on the left hand graph)

At 1 month old its just the bit at the bottom of the left diagram that is visible to infants and as they get older they can slowly see more.

The shape is the same but the amount infants can see compared to adults is very different.

This sort of data comes from the tela acuity cards

Therefore, a lot of the world is not accessible to the infant visual system

Question 14

Image seen as an adult (bottom right) compared to infants of different ages

Answer 14

At 1 month- lots of the fine detail is missing

This progression for 6 months of life is a quick progression.

Cataracts- film covering eye and stops light entering.

Question 15

Cataract removal

Answer 15

Even though vision is poor in early stage, missing this window seems to have an impact in your perception across your whole life, particularly on face perception.

Face discrimination works in a different way compared to people that have never had cataracts.

Adults who had cateracts removed would struggle to discriminate between these two faces.

The immaturity of the infant visual system may provide the best learning ground for discriminating faces. Teaches the weighting of configuration of faces over local processing

Question 16

Cataract- demonstration of critical period

Answer 16

Missing this early window where your vision is blurry and in visual development means that you then pay more attention to local details rather than the global configuration of whole layout of face.

This is a demonstration of a critical period in development- time visual system is particularly sensitive to one sort of sensory stimulus. If you don’t have this experience, it tends to be something you can’t then relearn later in life.

Question 17

Looking at whether or not having poor visual early on has an advantage for face perception.

Neural net- Vogelsganag et al. 2018

Answer 17

They trained a neural net (like an AI) on telling apart faces and the neural net is better at telling apart faces if you’ve given it blurry faces to start with.

So having blurry images early in life can be beneficial for our face discrimination.

Question 18

Colour Perception:
Cones, infant retina and pathways to colour- what is present

Answer 18

Although all the cones are present, the infant retina and pathways to colour are immature at birth. But, infants can see some colour from birth, and by 3-4 months old are trichromatic.

When babies are born, they have all 3 colour preceptors but they are just very immature.

Question 19

Colour perception:
The way the information from colour receptors is combined in later stages.

Answer 19

Three channels for colour vision(red-green, blue-yellow, luminance)

Parvocellular (midget) : colour, high sf

Magnocellular (parasol) : motion, luminance, low sf

Question 20

Adams 1989
Brown & Teller 1989

Babies and lights

Answer 20

Its a common misconception that babies cannot see in colour. If when babies are born, you show them a very intense red light with a very intense white light, they’ll look for longer at the red light. But if you show them when they’re born a blue light and a white light, they’ll look for equally long at both of them.

However babies do not see colours in the same way adults do. Babies need colours to be very intense in order to be able to see them.

Perception before 3 months of recognition is different to what adults will see.

Question 21

Colour Perception:
What colours can infants see easier?
What happens when you enter teenage years?

Answer 21

Colours on the right are harder to see because they’re less intense and they’re easier to see on the right because they’re more intense.

Need intense colours for infants to be able to see readily

Colour discrimination thresholds half with every doubling of age, but the ratio of input of the cones is the same across the lifespan

The size of the difference keeps shrinking until you’re in your teenage years (when colour vision is at it’s best) and then it starts to get poorer again.

Question 22

What might shape colour perception?

Answer 22

Environmental factors

Question 23

Study by Laeng et al
Difference between visual environments and being born in summer / winter

Answer 23

If you’re born above the artic circle in winter, there is a period of time where the sun doesn’t rise above the horizon, so this would be as light as it would get (on the right)

If you’re born in the summer, the sun often doesn’t set below the horizon so it’s daylight all the time (on the right).

This means you have two different visual environments and its different in the illumination you come across. People born in the more polar night would have more artificial illumination and be indoors more. Whereas people who are born in the midnight sun have all natural illumination and they’re outdoors more.

When you test these people as adults, theres a difference in their colour discrimination abilities that appears to be related to the visual environment they had.

Question 24

Why does it matter?
Implications for?

Answer 24

• Early years (and beyond) education
• Arts
• Baby products- targeted at boosting your babies brain
• Theory

Question 25

Early preference for specific stimuli
Newborn preference
e.g. Fantz 1956, Fantz & Nevis, 1967
Head turns in utero
Reid et al., 2017
What do the materials look like?

Answer 25

Fantz 1956, Fantz & Nevis, 1967- 2 triangles made up of three black dots on white background- one upside down and one the correct way

Reid et al., 2017- 2 triangles made up of three red blurry dots on black background- one upside down and one the correct way

Question 26

Why is there a bias for this triangle?

(Fantz 1956, Fantz & Nevis, 1967 / Reid et al., 2017)

Answer 26

Faces are shaped like this. This configuration of dots mimics how faces are seen by our visual system.

Mimics configuration of faces as seen by an immature visual system

Attending to a face is a valuable thing because it is where lots of emotion is displayed and where social symbols (speaking) come from.

Question 27

Video of baby being passed between a mum and the mums identical twin

Answer 27

This child understands that face is important but doesn’t understand the concept of identical twins yet.

So an infant this age is able to recognise and have a preference for specific faces.

Question 28

Early preference for specific faces- summary results

Answer 28

At 4 days old, infants look longer at mum’s face than a stranger’s face….
…but not when it’s just the internal features
…and only after multi-modal exposure

Question 29

Early preference for specific faces
What is found in relation to presenting internal features, presence of mum vs stranger

Answer 29

Just presenting internal features- babies don’t look for longer at mums face compared to a strangers face. This suggests infants look at global shape of mum to work out who they are.

Once taking away other features, it makes it harder for babies to tell apart two people

Only find this effect of preference for mum vs stranger when theres been multi-modal exposure.

Babies were taken away from their mums straightaway after birth for a couple hours and then brought back and you find they can no longer pick out mum. There has to be more than one sensory interaction with mum. The type of exposure you have matters in determining whether you can recognise them compared to a stranger, just seeing them isn’t enough.

Question 30

What is perceptual narrowing?

Answer 30

Experience, or lack of experience, shapes expertise i.e. ‘use it or lose it’ / refinement

Question 31

Early environmental experience
- what aged children discriminate faces of other species
- what makes a difference
- what similar effects

Answer 31

• 6 month olds discriminate faces of other species, 9 month olds do not.
• But, training between 6 and 9 months makes a difference
• Similar effects ‘Other Ethnicity Effect’

Question 32

Early environmental experience:
what was found in a study discriminating faces

Answer 32

People tend to better at telling the top two faces apart compared to the monkey faces.

6 month olds are equally good at discriminating faces of any other species. But when they come back into the lab at 9 months, they can no longer do this.

If you send babies home with a book when monkeys are named, then at 9 months they are still able to differentiate them, therefore training them makes a difference. Labelling is a valuable thing that signals to the infant that this thing is important.

Question 33

Early environmental experience:
What else can you get perceptual narrowing for?

Answer 33

Perceptual narrowing is not just specific to faces

Also get it with colour perception and phoneme discrimination- infants can discriminate two sounds but adults can’t

Question 34

• who has a preference for faces?
• what shapes expertise in face discrimination?
• what alone isn’t enough?

Answer 34

• Even very young infants have a preference for faces

— Preference for face like stimuli
— Ability to discriminate socially important faces from a stranger

• Experience (or a lack of experience) shapes expertise in face discrimination…
  — Ability to discriminate face is not species specific until 9 months old
• …but exposure alone isn’t enough. The type of experience matters
  — Newborns need multi-modal experience with mum
  — Cues like labelling aid the ability to discriminate faces