IV. Phonetic and Phonological Development Flashcards
What are some limitations researchers face when investigating speech perception in infancy? In other words, how might the capabilities of infants dictate the way we research speech perception?
Infants are very limited in their capabilities of what they can actually do and what researchers can measure.
- infants are not capable of communicating, pointing, lifting their heads, etc.; they cannot see very well
- researchers must research infants’ language comprehension through indirect, quantifiable measures such as heart rate, sucking, blood flow or electrical impulses or magnetic fields in the brain
high-amplitude sucking procedure
In which researchers insert a pacifier like device into an infant’s mouth to record sucking time as a measure for reaction to a stimulus
- infants have a sucking reflex that develops in the womb; when an object is inserted in their mouth, they will begin to suck on that object
- developed by Eimas et al. (1971) in their landmark study on speech perception in infants
What evidence shows that newborn infants have a preference for human speech?
Researchers (Vouloumanos & Werker, 2007) found that newborn infants at 104 days old had a preference for human speech over other sound
—used a high amplitude sucking procedure and found that infant’s sucking rates increased and slowed down for non-human speech, whereas they stayed high for human speech, indicating a higher interest in human speech
voice onset time (VOT)
the time between the release of a consonant constriction and when voicing starts on a following vowel
- voiced consonants have a negative VOT
What does it mean to say that adults have categorical perception of speech sounds? How does this differ from infants’ perception of speech sounds?
adults hear speech sounds as belonging to categories of sounds, rather than hearing a continua of sounds
- adults perceive phonemes; they are sensitive to across-category changes but not within-category changes
infants also hear across-category changes in speech sounds (e.g. from /ba/ to /pa/)
- Eimas et al. (1971) habituated 1-4 mo. old babies to speech sounds of one category and then changed the sound to either. a within-category or across-category sound; infants did not show a change in sucking rate for within-category changes, but they did show an increase in sucking rate for across-category changes
- infants, however, are more sensitive to differences in speech sounds than adults
What evidence is there for linguistic perceptual narrowing in infants? (Werker and Tees!)
Researchers (Werker & Tees, 1984) found that infants’ ability to distinguish between speech sounds not in their native language declines from 6 months to 12 months.
- Infants were tested on Salish and Hindi contrasts not found in English during test trials, and English contrasts during control trials
- Werker and Tees used a heard-turn paradigm, in which they conditioned children to turn their head to a change in speech sounds by rewarding correct head-turns with a dancing mechanical bunny.
- 60-80% of infants at 6 months “reached criterion”, whereas only 10-20% of infants at 12 months reached criterion
- evidence for perceptual narrowing
perceptual narrowing
the process by which we begin to disregard distinctions between stimuli that are not relevant to us.
- for language, this is the process by which we develop phonemic representations of sounds and stop hearing distinctions between sounds that are not relevant to our language(s)
- perceptual narrowing occurs across domains
- occurs during a critical period
—visual: perception of faces; e.g. babies are sensitive to changes in monkey faces
critical period
the period of early development in which the brain is especially sensitive to stimuli
- high neuroplasticity
- specialization occurs: infants develop a sense of what kind of information is relevant to their experience
theories of linguistic perceptual narrowing
- maintenance-loss view
- perceptual assimilation view
maintenance-loss view in linguistic perceptual narrowing
in which perceptual narrowing occurs due to “atrophying” of neural structures which respond to changes in speech sounds
- when distinctions between sounds are not relevant to an infant’s language, their brain stops responding to these distinctions and the neural structures responsible for recognising distinctions weaken
- weakness: adults can learn to distinguish between sounds later in life
perceptual assimilation view in linguistic perceptual narrowing
in which perceptual narrowing occurs due to the brain forming categories (phonemic representations) for sounds, and sounds not relevant in an infant’s language “assimilate” into those categories
- ability to perceive sounds is not completely lost
- supporting evidence: adults can develop the ability to perceive non-native speech sounds later in life
Is perceptual narrowing universal?
linguistic perceptual narrowing has not been investigated in infants for all of the world’s languages
- not all regions have been tested, and not all contrasts in all languages have been tested
- findings cannot be generalised to all of the world’s languages
What are some features of infant directed speech (IDS)?
- higher pitch
- repetition of sounds, words, or sentences
- slower
- pauses
- simpler sentences
- emotion and facial expressions
- back-and forth dynamics
What evidence is there to support why adults engage in infant-directed speech?
Research shows significant changes (facial expression, pitch of voice, speech rate) in IDS and regular speech. Adults engage in IDS for the following reasons:
1. heightened pitch: grabbing attention, conveying emotion
2. slower speech rate: acoustic clarity, allotting more time to process linguistic input
3. exaggerated facial expressions: attention grabbing, conveying emotion (perceptual support)
—providing cues for articulation: mouth and jaw movements cue infants into perceiving certain sounds
4. greater vowel space: acoustic clarity
5. simpler speech structures: less to process; increased predictability
How do researchers habituate infants to new stimuli? Why is it necessary for researchers to habituate infants to stimuli in studying phonetic development?
Researchers habituate infants to stimuli by measuring some continuous behaviour that changes in response to stimuli (e.g. sucking rate), and exposing infants to a particular stimuli until that behaviour returns to base level.
It is necessary for researchers to habituate infants in studying phonetic development so that researchers do not mistake an infants’ reactions to speech sound/sound in general for an ability to discriminate between speech sounds, or an ability to discriminate between human speech and regular sounds.
