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?)
