week 2 - infant perception Flashcards
What is sensation?
information about the environment picked up by sensory receptors and sent to the brain
What is perception?
The brain’s interpretation of sensory input - our understanding of the world
Do newborns possess perceptual abilities?
yes, newborns possess many perceptual abilities
how can we test infant perception?
- preference technique
- habituation
- conditioning
- event-related potentials (ERPs)
What is the ‘preference technique’ used to test infant perception?
it involves presenting infants with two stimuli and measuring which one they look at longer to determine preferences
How does habituation demonstrate infant perception?
infants habituate to a stimulus (e.g. noise) over time, but their interest renews when a new stimulus is introduced
How does conditioning demonstrate infant perception?
- rewarded when infant turns head to the side (e.g. peekaboo)
- link reward with noise until habituated
- change noise
What are event-related potentials (ERPs) and how do they show infant perception?
most commonly used brain imaging technique used with infants
- e.g. Breen et al., 2014
- electrical activity from nervous firing when brain is active
- ERPs have good temporal resolution, poor spatial resolution
- good temporal resolution makes them useful for studying infants’ neural responses
ERPs can be used for measuring evoked potentials:
- brain activity time-locked to particular stimuli
- infants listened to words spoken correctly or with unusual stress patterns (Weber, Hahne, Friedrich & Friederici, 2004)
- 4-month old infants show ‘no suprise response’
- 5-month old infants do
At what age do infants begin to show a ‘suprise response’ to unusual stress patterns in speech?
at 5-months old, infants, like adults, show a ‘suprise response’ to unusual stress patterns in speech
When and how do fetuses respond to sound?
22-24 weeks, fetus responds to sound (Hepper & Shahidullah, 1994)
- measured by heart rate & movements
- Foetus can hear a low frequency range (250-500 Hz), which expands as the foetus matures (Hepper, 2005)
- sound that reaches foetus is distorted due to skin, muscle, and amniotic fluid, providing a noisy environment
How did DeCasper et al. (1994) study prenatal learning?
- mothers recited the same story to theur unborn babies three times a day for four weeks (33rd to 37th week gestation)
- foetus’ heart rate measured as DV
- test phase: target and control stories were played to foetus through mothers abdomen
- story 1 (30 secs) -> silent break (75 secs) -> story 2 (30 secs)
- heart rate decreased when target story played, regardless of order of presentation
- no change in heart rate when control story is played
What is the Non-nutritive sucking technique?
- rubber teat placed in infant’s mouth
- filled with fluid and connected to a pressure-sensitive device
- sound is played
- babies learn quickly that each time they suck they hear a sound
- after a while the infant habituated to the sound and suck less often
- when a new sound is played - the infant can discriminate the sound and will suck more frequently again
How did DeCasper & Spence (1986) revise their prenatal learning study?
- 33 pregnant women read a target story to their unborn babies twice a day during the last 6 weeks of pregnancy
- non-nutritive sucking technique used with new born infants
- infants preferred the story they had heart in utero to a control story, sucked harder to hear target/familiar story
- control group (infants matched for sex, age, ethnicity) showed no difference in responses to stories
Which sense is better after birth, auditory or visual?
Auditory acuity after birth is better than visual
- newborns turn head towards sound - showing they can locate sounds from or soon after birth
How do newborn’s react to their mother’s voice compared to a stranger’s (DeCasper & Fifer, 1980)
- newborns prefer their mother’s voice over a stranger’s, indicating prenatal learning of the mothers voice
- 3 day olds suck more to hear mum than stranger
- no preference between dad and stranger, suggests baby learnt mums voice prenataly
Do babies prefer mum’s voice before or after birth? (Moon & Fifer, 1990)
Prefer mum’s voice as heard in the womb (distorted) rather than after birth
What did Mehler et al. (1988) find about speech perception of known and unknown languages in babies?
- 40 4-day-old french babies from monolingual families
- speech stimuli (french-russian speaker talking about events from her life)
- 4 conditions: F-F, R-R, F-R, R-F
- non-nutritive sucking technique
- infants could discriminate between familiar & unfamiliar language
- infant preferred familiar language, sucked more to hear french
- no effect observed when experiment was repeated with infants where french was not the home language
What did Kitamura et al. (2013) find about infants’ ability to discriminate accents
6-month-olds show a preference for familiar accents, but by 9 months, infants are better at ignoring accent differences
What method did Kitamura et al. (2013) use to study infants’ ability to discriminate accents?
- explore the abilities of 6 and 9 month olds to discriminate between accented speech in their own native language (Australian English, American English, and South African English)
- Infant fixation-controlled serial preference procedure
- study 1: 6 month olds looked longer at AusE than SAE
- study 2: 9 month olds shown no significant difference in fixation time for AusE and SAE
- study 3: 9 month olds played accented speech (AuE v SAE) until there was a 50% reduction in fixation (becoming bored) then half played same accented speech and half played the other accented speech. No significant difference
- study 4: 6 month olds showed no significant difference between AusE and AmE fixation times
- study 5: 3 month olds fixated significantly longer on AusE than AmE
- 6 month olds discriminate between AusE and SAE but not AusE and AmE
6 month olds show accent preference, only when unfamiliar accent utilised
9 month olds ignore accent differences regardless of exposure
- when exposed to different accents earlier on, this developmental pattern shifts e.g. 6-month-olds ignore differences between AusE and AmE, high exposure due to tv, films, music in the home
- later in development, accents become more important for social reasons
By what age do children prefer their native accents versus foreign accents? (Kinzler, Dupoux & Spelke, 2007)
5 years old
What visual preference do newborns have compared to older infants?
- newborns have poor visual acuity (fuzzy and blurred, most deprived sense in utero)
- limited colour to detect colour in newborns (Adams et al., 1994)
- colour vision similar to adults by 4 months (Teller & Bornstein, 1987)
- infants under 2 months cannot track moving objects smoothly (jerky eye movements, Aslin, 1981)
newborns prefer less complex paterns, while older infants develop a preference for more complex stimuli as their visual acuity grows
How does infants ability to scan objects develop?
- to perceive objects, it is necessary to scan the object
- very young infants focus on part, not the whole
- 1 month olds start by focusing on a single feature and then tend to scan the outer edges of an object
- 2 month olds move in to scan the internal features (Salapatek, 1975)
- possibly indicates a shift from where things are to what things are (Haith, 1979)
How does infant pattern perception change with time?
- using a looking chamber, Fantz (1961) identified that infants show a preference for patterned over plain stimuli (e.g. stripes, checker)
- Fantz & Fagan (1975) found that as the visual system develops, a preference for complex stimuli increases
- 1 month prefer less complex (8x1” squares)
- 2 month prefer complex (32 smaller squares)
- could be due to increased visual acuity
How did Fantz (1961) study face perception in infants?
- 3 stimuli based on faces (face, scrambled face, non-face)
- 1 to 15 week old infants
- slight preference for natural face over others
- strong preference for face-like (real & scrambled) over non-faces
- (prefered because more complex?)
How did Maurer & Barrera (1981) study face perception in infants?
- 3 complex stimuli - one face, two scrambled faces (symetrical or asymetrical)
- timed how long 1 and 2 month old infants fixated on each
- results showed fixation was not due to complexity
- 1 month olds showed most preference for asymetrical scrambled face, then face, then symetrical scrambled face
- 2 month old showed large preference for face, then asymetrical scrambled, then symetrical scrambled
What do studies show on infant preferences for male and female faces?
- from 3-4 months, visual preference for female faces (Johnson et al., 2021) (Quinn et al., 2002)
- evidence from parental reports and observations indicates infants spend more time with females (Sudgen et al., 2014)
- infants have been found to process female faces as individual stimuli whereas male faces are processed at summary catagory level (Quinn et al., 2002)
How did Slater et al. (1998) study infant face perception in relation to ‘attractive faces’?
- infants show a preference for ‘attractive faces’ (judged by adults) by 2 months, regardless of sex, age, or race
- attractive faces may be most like the prototype we have for human faces
- i.e. infants are not judging based on attractiveness, but based on preference for a human face
How did Giffey & Little (2014) study infant preference for attractive faces? What did results show?
- facial symmetry, facial averageness and sexually dimorphic traits affect adult raitings of faces
- 64 infants, 12-24 months
- stimuli: male and female faces manipulated for 3 traits
- presented in pairs and fixatio measured via eye-tracking
results:
preference for non-average, symmetrical and feminised faces
- preference for non-average was suprising. though attractive faces were those that looked most like a template for a face. novelty. is the average face similar to faces seen in previous trials?
- preference for feminised faces reflects exposure to female faces during infancy and/or preference that infants have for more baby type faces (feminine more similar to these than masculine)
- broad agreement between infants and adults on attractiveness, experience with the world and the cognitive changes affect preferences
How did Pascalis et al. (1995) study face recognition in infants?
- can infants recognise their mother using only visual information?
- Study 1: 34 infants (72 to 120 hours old)
- live presentation of 2 female faces
- faces matched for complexion, hair colour, and style
- olfactory cues blocked
- infants looked at mother significantly longer than at a stranger
- Study 2: repeated with females wearing a pink headscarf
- infants no longer looked longer at mother’s face
- suggests babies use external face contours not internal features
How do face masks impact learning and face recognition? (Debolt & Oakes, 2023)
- adults and children impaired at learning and recognising masked faces (Stajduhar et al., 2022)
- utilised visual paired comparison task with 6 to 9 month old infants
- 2 (familiarisation stimuli: masked v unmasked) x 2 (test stimuli: masked v unmasked) design
- familiarisation phase (two identical images, masked or not)
- test phase presentation of familiar face with a novel face (masked or not)
- infants showed preference for novel faces only when faces during the test phase were not masked
- infants were relatively unaffected by faces being masked during the familiarisation phase
- infants also looked at the upper part of the face more when masks were present
- holistic face processing evident: recognise a whole face when initial encoding is only part of face but unable to recognise part of face (e.g. masked) when initial input was whole face
How did Pascalis et al. (2002) study infant abilities to differentiate between human and monkey’s faces?
- adults are poor at discriminating non-human faces
- 6 & 9 month old infants and adults
- habituation/novelty-preferrence paradigm
- 6 month olds distinguish between human faces and monkey faces
- 9 month olds and adults only discriminate human faces
How did Timeo et al. (2019) study the Own Race Effect?
other race faces remembered less well than own race faces (Meissner & Brigham, 2001)
- 5 & 9 month old caucasian infants brain activity measured using FNRIs
- shown male and female caucasian and african faces for a maximum of 4 minutes & parents completed a scale measuring experience with other races
- African faces resulted in greater brain activity than Caucasian
- 9 month olds activation occured in the right-hemisphere
- greater activation overall for 9-month-olds
- brain specialization occuring between 5 and 9 months
other studies have reported older children and adult’s greater activation for own race (Zhou et al., 2016), in infants, greater activation may be due to novelty
How did Bower (1965) study size constancy in 6 to 8 week old infants?
- infant conditioned to turn head and receive peekaboo as a reward
- infant then conditioned to turn head only when 30cm cube presented and receive peekaboo as a reward
- response to cube placed further away is then measured. 30cm cube, 3m away. if infant had size constancy, they would still turn head
- response to 90cm cube placed further away measured. If the infant does not have size constancy, they would still turn head
results showed that infant is 3x more likely to turn head to 30cm cube 3m away, than 90cm cube 3m away
How did Kellmen & Spelke (1983) study object separation in infants?
- when moving in unison, adults presume one object (a block moving in front of a rod)
- infants are shown habituation displays: the block and rod moving together
- test displays are done, showing a rod and a broken rod moving
- from 3 months (2 months in later studies), infants look more at the broken rod, suggesting they thought the rod was complete
- new-borns look more at the completed rod, suggesting they treated it as 2 separate objects (Slater et al., 1990)
How do infants develop depth perception, according to Gibson and Walk (1960)? The visual cliff paradigm
- infants aged 6-14 months (from crawling age)
- infant placed in the centre of the platform and encouraged to climb over the deep side
- if the infant does not have depth perception: expect to crawl across the deep side to get to mother
- if the infant has depth perception: expect to refuse to crawl over deep sides
- depth perception is evident in 6 month old infants
questions: is depth perception innate? has it been learned over the first 6 months?
How did Schwartz et al. (1973) test depth perception in infants?
- 5 and 9 month old infants
- placed over deep and shallow side of platform
- DV = heartrate
- 5 month old infants showed a decrease in heart rate
- they noticed a difference, but not fearful
- 9 month old infants showed an increase in heart rate
- they noticed a difference, fearful or excited?
- because of greater experience with the environment?
How does experience effect depth perception?
in humans, depth is not innate, it is learnt through experience
- providing young infants with experience in a baby walker led to increased reluctance to cross the visual cliff (Rader et al., 1980)
- infants with more than 3 months of experience of walking are more successful at combining sensory info with motor actions to enable them to negotiate an obstacle in their path
How does olfactory perception develop in infants?
- newbors turn head away from noxious substances e.g. ammonia (Riser et al. 1976)
- within first few days of life, infants will turn towards mother’s scent more often than another mother (McFarlane, 1975)
- within first 2 weeks, infants recognise their mothers scent (Cernoch & Porter, 1985)
- infants are soothed by their mother’s smell on clothes (Sullivan & Toubas, 1998)
but learning still takes place over development:
- many pre-schoolers do not find smells unpleasant than adults do
What is cross-modal perception (Meltzoff & Borton, 1979)?
- 1 month old infants given 2 dummies to suck
- different textures, smooth vs nobbled
- infants could not see dummies when placed in mouth
- in the second phase of the experiment, infants shown enlarged pictures of the two dummies
- most babies prefered to look at the dummy they had just been sucking
- i.e. had ability to match perceptual info across modalities
What is cross-modal perception (Bahrick, 1983)?
- 3 to 4 month old infants played two video clips side by side:
- concrete blocks banging together
- sponges squashed together
- then infants were played the sound that corresponded to one of the clips (i.e. banging or squashing)
- infants looked at the clip that corresponded to the auditory information
