Perceptual development -PD

• Perceptual abilities in infants can be inferred from measures such as head-turning, sucking, eye-tracking, heart-rate.
• Perceptual development research faces challenges due to attentional and motivational limitations, motor limitations, and linguistic limitations.
• Measures for perceptual development include preference method, habituation method, and conditioning method.
• Visual perception in infants is approximately 30 times worse than in adults due to a limited field of view, fixed focal length, and no stereoscopic depth perception before 4 months.
• Face perception is significant in the infants world as it aids in distinguishing people from other objects, identifying individuals, and interpreting others emotions.
• Fantz (1961) argued that there is an innate preference for faces.
• Maurer and Barrera found that 2 month-old infants preferred real faces more than complex symmetic forms.
• challenges of perceptual development research?

  • attentional and motivational limitations
  • motor limitations
  • linguistic limitations
• measures of infant perceptual abilities:

  • head-turning
  • sucking
  • eye-tracking
  • heart-rate
• methods of inferring perceptual abilities:

  • preference method
  • habituation method
  • conditioning method
• foetal visual perception

  • ultrasound studies reveal:
  • eyelids remain clsoed until week 26
  • eye movements at 18 weeks
  • can sense light sone on mothers abdomen. responds by moving and heart-rate increase
• newborn visual perception

  • acuity approx 30 x worse than adult
  • limited field of view
  • focal length fixed around 21 cm (muscles controlling lens permit accomodation)
• visual acuity

  courage and adams

  newborn: 30 times worse than adult

  2mo: 15 times

  4mo: 8 times

  8mo: 4 times
• faces have great significance in the infants wolrd:

  • distinguish people from other objects
  • identify individuals, thus facilitating caregiver attachment
  • interpret others emotions
• Fantz argued there is an innate preference for faces
• perceptual development

  face perception

  • but is there a true face preference, or rather, a preference for stimulus complexity and symmetry
  • Maurer and barrera: 1 and 2 mos
  • 2mo: preferred real face: more than just preference for complex symmetric forms
  • 1mo: no preference: no support for innate face preference
• does the fetus have a representation of the human face?

  reid et al - foetus from 29 weeks preferentially turns towards face-like stimulus
• can infants recgonise different faces?

  pascalis et al

  newborns - 4 days old

  can recognise mothers face from unfamiliar female face

  but not when scarves cover external features of face
• pascalis study suggests

  • newborns learn to recognise faces very rapidly
  • newborns use external, rather than internal facial features
  • perhaps newborns cannot use internal face features
• slater et al - attractiveness

  • adult rating face a: 57% face b: 42.9%
  • same external features, different internal features
  • suggests newborns are sensitive to internal features
• depth perception

  arterberry yonos and bensen

  5 & 7 MO

  • 2 objects at same phsycial distance monocular viewing
  • if use pictorial cues, should reach for lower object more often
  • 5 mo: reach for upper and lower equally
  • 7mo: reach for lower 72% of time
  • use of pictorial cues emerges between 5 and 7 mo
•  

  Foetal auditory perception

  • Much auditory stimulation while in womb e.g. loud external sounds, mothers internal organs, mothers speech
  • Initially, foetus responds (by moving and increased heart-rate) only to low-frequency range of adult hearing, but this range expands as the foetus matures
  • Foetal abilities can be inferred from behaviour at birth
  • Many studies show auditory perceptual development is influenced by auditory experience in the womb
• Newborn auditory perception

   at birth:

  • Prefer to listen to people
  • Prefer speech to other sounds
  • Respond most to tones
  • Prefer sounds with a range of tones (like speech)
  • Newborns will preferentially suck to hear voice recording
  • Less likely to suck for music or rhythmical non-speech sounds
• Speech perception

  • Evidence that the foetus can learn to recognise the mother's voice
  • DeCasper and Fifer
  • Mothers read from story book aloud, often, during final stages of pregnancy.
  • On the first day after birth, preferential sucking to hear same story read by either

  1. Mother or 2. female stranger

  Newborns preferred mothers voice

  
  

  But all infants had -12 hours postnatal exposure to mother
• DeCasper and Prescott - speech perception

  • 2 days olds showed no preference for father voice vs male stranger, despite hours of postnatal experience with father
• Infants are sensitive to the phonetic contrasts of all languages

  Werker et al

  • Examined 7 mo old and adult sensitivity to a hindi contrast
  • Almost all 7mo olds detect change
  • All native hindi speaking adults detect change
  • 1 in 10 native english speaking adults detect change
• • Why do infants lose ability to discriminate non-native phonemes?
  • Perhaps: auditory system develops greater sensitivity to sounds of native-language; allows accurate detection of same phoneme spoken by different people in different ways
• • Juscxyk et al compared pref. for common vs uncommon phoneme sequences in english (e.g. chun vs yush)
  • Jusczyk et al compared pref for common vs uncommon stress pattern in english
  • 6 month olds: equal pref
  • 9 month olds prefer listening to native-language speech sounds
  • Suggests innate speech predisposition; sensitivity to subtleties of native speech sounds improves through experiencemnb
• Perceptual development

  • The newborn is far from incompetent
  • Infant perception is limited but well suited to needs
  • Some perceptual abilities may be 'pre-wired': gives the newborn a 'head-start' e.g. evidence for innate sensitivity to faces and speech sounds
  • Some perceptual abilities are heavily dependent on experience e.g. visual acuity
  • Perception is well organised at birth, though very different from adult