Infant abilities and experimental techniques

• Experimental techniques for testing infants

  • Special techniques necessary for studying infants
  • Limitations of simply observing infants
  • Methods used
  • Dependent variables that can be measured
• Paul Bloom: '"It is difficult to learn about the mental life of any creatures that cannot use language, but a baby poses special challenges. Mature nonhumans, although nonverbal, are physically adroit. Chimpanzees can easily express their preferences through coordinated action; pigeons peck; rats run through mazes, and so on. But young babies just lie there, crying and gurgling".'
• What infants can do

  • Turn head and move eyes - Orienting reflex
  • Suck - Innate sucking reflex
  • Cry, feed and sleep
  • Engage with the world - reflexes
• Can we use these things to test what infants are capable of? Use reflexes they are born with and test of what they are capable of at a more cognitive level
• Methods for studying infants

  • Looking time methods
  • Spontaneous visual preference
  • Habituation - novelty
  • Violation of expectation
  • Preferential sucking
  • Eye movement
  • Physiological measures - EEG fMRI
• Spontaneous visual preference

  • Infant presented two visual stimuli, reasonably well spaced to left and right in the visual field
  • Stimuli often lead to preferential looking
  • Possible to measure which stimulus the infant looks at longest and therefore prefers/finds most interesting
  • Yields a measurable dependent variable
  • High contrast colours - when infants are young (black and white vision)
• Infants prefer faces (Fantz, 1963)
• Infants just 12 hours old found to prefer looking at their mother's face than a stranger's (Bushnell, 2003)
• When presented with their mothers face and a stranger's face, 4-day-old infants looked longer at their mother's face (but not when both wore a headscarf). Pascalis, de Schonen, Morton, Deruelle, & Fabre-Grenet (1995).
• These findings were replicated with infants of 19–25 days and older infants 35-40 days old. Both were able to make the discrimination with mother and stranger when they wore headscarves. Bartrip Morton & De Schonen (2001).
• Preferential looking

  • Fantz's 'Looking Chamber' pioneered the preferential looking method
  • Method reveals that infants can see and that they have preferences (pick their caregiver)
  • Led to lots of studies into infant perception - researchers realised infants COULD see, hear, smell etc and had preferences (c/f earlier view of William James)
• Preferential looking findings


  • Newborns prefer patterned rather than plain stimuli (Fantz, 1961)
  • As they age prefer more complex patterns (Banks & Salapatek, 1983)
  • Size Constancy - suggest to be innate ability (Slater, Mattock & Brown, 1990) and refined up to 11 years (Kellman & Banks, 1998)
  • Infants younger than 7 weeks of age probably cannot not process colour information, by four months of age children have colour vision similar to adults (Teller 1997)
• Infant preferences


  • Prefer face-like to non-face-like visual arrays (Johnson, Dziurawiec, Ellis & Morton, 1991)
  • Attracted to a prototypical eye-contact stimulus (prefer faces upright vs upside down (Grossmann, Johnson, Farroni & Csibra, 2007)
  • Prefer faces with eyes open vs. shut (Batki, Baron-Cohen, Wheelwright, Connellan & Ahluwalia, 2000)
  • Prefer facing forward vs. being averted (Farroni, Csibra, Simion & Johnson, 2002)
• The Visual Cliff task

  Infants who just began to crawl were more likely to crawl over the edge whereas other babies who crawled for longer are unlikely to probably because of the experience of the world they have and now they have depth of perception
• Habituation


  • The process in which attention to novelty decreases with exposure
  • Infants prefer to pay attention to novel sights, sounds, smells and temperatures rather than familiar ones
  • Present the same stimulus repeatedly until the infant habituates to it, introduce novel stimulus, which should re-engage their attention
  • Used to test infants' sensory abilities and memory
  • Habituation = evidence of memory: If infant looks for shorter periods over trials, implies progressively more of stimulus committed to memory
• Using the habituation method Bushnell et al. (1984) showed that infants as young as 3 weeks could remember information about stimuli they had been shown, including aspects such as colour/shape/size.
• Kellman & Spelke (1983) - Infants are habituated to the first experiment where it is only one rod moving and for experiment 2 two rods were moving which made infant pay more attention to it.
• Bertenthal, Campus & Haith (1980) - top-down process = from 3 months old and filling in the blanks and applying laws
• Habituation


  • Provides an indicator of familiarity - the infant has encoded the properties and stored them in memory
  • As typically-developing infants get older they habituate faster (Colombo et al, 2004)
  • Visual recognition memory indicates functioning of neural structures/pathways
• Habituation as a diagnostic tool

  • Habituation rate is an indicator of brain integrity and cognitive competence
  • Birth difficulties can result in slower habituation - may indicate neurological defects
  • Speed of habituation predicts IQ up to age 11 (higher IQ habituate faster)
  • ADHD – slower habituation, get bombarded with sensory stimuli as they cannot block it out
  • Early habituation speed predicts later IQ after up to 10 years (Bornstein & Sigman, 1986)
  • Visual recognition memory (degree of preference for novelty) predicts IQ at age 11 (Rose & Feldman,1985)
• Problems with habituation


  • How do you tease apart increased looking time due to novelty vs similarity?
  • Ensure habituation has occurred – 50% reduction in looking time
  • Avoid using test stimuli with a priori preference (e.g. Quinn et al., 2002 – male and female caregivers)
  • Use two test stimuli – new and original objects (show stimuli side by side)
• Object permanence


  • According to Piaget infants do not search for hidden objects before stage 4 (around 9 months)
  • Later psychologists argued failure to search for hidden objects stems not from a lack of object permanence but from an inability to perform coordinated actions
  • Baillargeon, Spelke & Wasserman (1985) developed method to test object permanence that did not rely on infants' manual abilities
• Violation of expectation


  • When something that an infant expects to happen doesn't happen, they show 'surprise'
  • Infant seen test trials of moving objects
  • Then presented with an 'impossible' and a 'possible' event
  • Surprise or visual preference for an 'unexpected outcome' = prolonged looking, increased heart rate
  • Allows us to measure object knowledge in very young infants and how they reason about physical events
  • Reveals infants as 'budding physicists'
  • Infants show impressive awareness of rules that govern physical entities
  • 3 and half months have object permanence unlike what Piaget suggested
• Infants look longer at the event they perceive as more novel or surprising.
• Infants show preference for unnatural event at 7 months but not at 5 months (Kim & Spelke, 1992).
• Baillargeon's Drawbridge task


  • Infants familiarized with repeated event - a flap rotated from flat on the table through 180 degrees
  • 2 types test event presented, in both a cube was placed in the path of the flap
  • 'Possible' test event: flap rotated but came to a stop when met the cube
  • 'Impossible': flap rotated full 180 degrees
  • Infants as young as 3 ½ months looked more at impossible event: Infants understand object permanence and know that one object cannot move through another
• Criticism of drawbridge task - Methods used previously to measure object permanence fail to rule out the effects of perceptual novelty and/or familiarity. (did not test until there was a 50% reduction and were definitely habituated)
• This has led to the search for alternative measures of infant expectation, such as eye-tracking methods (Dunn & Bremner, 2016) and brain indices of error detection (Berger, Tzur & Posner, 200)
• but not at 5 months (Kim & Spelke, 1992)
• Baillargeon's Drawbridge task


  • Infants familiarized with repeated event - a flap rotated from flat on the table through 180 degrees
  • 2 types test event presented, in both a cube was placed in the path of the flap
  • 'Possible' test event: flap rotated but came to a stop when met the cube
  • 'Impossible': flap rotated full 180 degrees
  • Infants as young as 3 ½ months looked more at impossible event: Infants understand object permanence and know that one object cannot move through another
• Taken from Baillargeon (1993)
• https://www.youtube.com/watch?v=hwgo2O5Vk_g Criticism of drawbridge task
• Methods used previously to measure object permanence

  Fail to rule out the effects of perceptual novelty and/or familiarity (did not test until there was a 50% reduction and were definitely habituated)
• Alternative measures of infant expectation


  • Eye-tracking methods (Dunn & Bremner, 2016)
  • Brain indices of error detection (Berger, Tzur & Posner, 2006)
• High Amplitude Sucking (HAS)

  • Sucking an innate reflex
  • Infants can vary rate and pressure at which they suck
  • Dummy is connected to a pressure transducer (measures how frequently they are sucking and at what pressure)
  • When it reaches a predetermined level a stimulus appears
  • Can be used in habituation procedures – they suck to hear a stimulus and once habituated the sucking becomes less intense
• HAS: Evidence


  • Eimas et al. (1971): 2 month olds can discriminate phonemes [p] in pat from [b] in bat
  • 6-8 month old infants in Japanese-speaking environments can discriminate [ra] and [la]
  • Newborns prefer their mother's voice (DeCasper & Fifer, 1980)
  • Newborns remember stories they heard in the womb (DeCasper & Spence, 86)
• Eye Tracking/Corneal reflection


  • Invisible infra-red light beams shone into eye
  • Reflected images picked up by tv camera
  • Possible to compute eye orientation from position of reflected beams relative to reference points on the cornea
  • Precise measure of where infant looking but invasive
• Salapatek (1975) was one of the first to study eye movements and to reveal how infants scan the human face, and how this changes as visual acuity improves
• Visual Perception and eye scanning

  • A newborn infant has poor visual acuity and views the world which is more fuzzy and blurred than an adult's
  • Infants younger than 2 months unable to track a moving object smoothly. Jerky eye movements (Aslin, 1981)
  • Salapatek (1975) looked at eye movements as they scanned geometric shapes. At one month tended to focus on a single feature or boundary
• The use of eye tracking


  Eye tracking is a promising technology for early identification of atypical learning and behaviour because it is feasible and valid in preverbal populations, provides and objective measures, can be used quantitatively and reduces reliance on parent report (Gillespie-Smith et al., 2016)