Basic Perceptual Abilities of Young Infants: Understanding Infant Perception and Cognition

1. HUMAN DEVELOPMENT 1PSYCHOLOGY 3050:Infant Perception and Cognition Ch 4 Dr. Jamie Drover SN-3094, 864-8383 e-mail – jrdrover@mun.ca Winter Semester, 2015

2. Basic Perceptual Abilities of Young Infants • It was once thought that infants were born deaf and blind and with limited pain sensitivity. • Although far from mature, all of the infant’s senses are functioning. • They even prefer some sights, smell, and sounds over others. • Infants are also sensitive to pain • ELBW infants’ response to pain is affected by repeated painful episodes.

3. Basic Perceptual Abilities of Young Infants • Vision and hearing develop rapidly over the first year. • Tactile stimulation is very important to infants. • Pre-term infants who receive massage gain more weight, spend more time awake, and display more advanced cognitive and motor skills than do normal treated preterm babies (Schanber & Field, 1987).

4. Basic Perceptual Abilities of Young Infants • The chemical senses (taste and smell) develop early. • Six-day olds prefer the scent of their mother’s breast pads over those of a stranger (Macfarlane, 1975).

5. Methodologies of Infant Perception • To assess infant perception, we must observe a behavior that an infant can control and use that to infer perception. Sucking Response • Researchers often use infants’ sucking rates. • DeCasper and Spence (1986) had pregnant women read one of three passages aloud twice per day.

6. Methodologies of Infant Perception • Shortly after birth, headphones were placed on the infants. • One of several passages could be played over the headphones based on sucking rates. • Infants would alter their sucking rates in order to hear the reading of familiar passages.

7. Methodologies of Infant Perception Visual Preference Paradigm • Fantz (1958, 1961) placed babies in a looking chamber and presented them several visual stimuli. • If they spend more time gazing at one pattern more than another, it is assumed they can discriminate between them.

8. Habituation/Dishabituation • Habituation: the decrease in response to a stimulus as a result of repeated presentations of that stimulus. • Infants can habituate to a visual stimulus. • The longer infants are exposed to a stimulus, the less time they will spend looking at it. • Habituation occurs when there is a substantial decrease in looking time following repeated presentation.

9. Habituation/Dishabituation • Often defined as when fixation to the stimulus is 50% of what it was initially. • If a new stimulus is then presented, the infant may show a sudden increase in looking time. • This is dishabituation. • Thus, the infant can discriminate between the two stimuli. • Also indicates that infants can remember the earlier stimulus.

10. Habituation/Dishabituation

11. Habituation/Dishabituation

12. Habituation/Dishabituation • Using this paradigm, Friedman (1972) found evidence that 1- to 3-day-old infants will habituate and dishabituate to visual stimuli. • Newborns are capable of visual memory.

13. The Development of Visual Perception • Infants can perceive light (pupillary reflex) but because of poor accommodation, much of what they see is blurry. • Accommodation is adult-like at 3 months. • Newborns can track a moving object, but the eyes do not always move in harmony. • Convergence and coordination are adult-like by 6 months.

14. Testing Infants’ Visual Acuity • Visual acuity of newborns is 20/600 to 20/400. • Can be tested using forced- choice preferential looking. • Infants are presented with rectangular cards that contain black and white stripes on one side of a central peephole, while the other side is blank. • Teller Acuity Cards

15. Testing Infants’ Visual Acuity • Given an infant’s preference for patterned stimuli over unpatterned stimuli, if he/she can detect the stimulus, he/she will fixate it. • A naïve observer must determine the location of the stripes based on the fixation of the child.

16. Testing Infants’ Visual Acuity • The thinnest stripewidth at which the observer can determine the location of the stripes provides a measure of visual acuity.

17. The Development of Visual Perception • Vision is poor at birth because the fovea is underdeveloped. • Point on the retina where vision is sharpest. Packed with cones. • The infant fovea contains large, less densely packed cones. • Newborns can discriminate between red and white, but can not differentiate blue, green, and yellow from white (Adams et al.1994).

18. The Development of Visual Preferences • Until 2 months of age, an infant’s visual preferences are affected by physical properties of the stimulus. • Babies prefer moving stimuli over stationary stimuli. • See Haith (1966) p. 193. • Infants prefer high contrast stimuli over low contrast stimuli. • See Salapatek and Kessen (1966) p. 193.

19. The Development of Visual Preferences

20. The Development of Visual Preferences • Infants at 1 month of age focus their attention primarily on the outside of a figure. • Externality effect.

21. The Development of Visual Preferences • At 4 months, infants start to show a preference for vertical symmetry. • They prefer to process stimuli that are vertical and symmetrical as opposed to asymmetrical and horizontal stimuli. • Curvature, or curvilinearity is a also important to infants. • Fantz demonstrated that infants sometimes prefer cuved stimuli over linear stimuli.

22. The Development of Visual Preferences • Infants as young as 3 to 4 months of age prefer the curvilinear and concentric stimuli (Ruff & Birch, 1974). • Even newborns prefer curvature.

23. Psychological Stimulus Characteristics • At around 2 to 4 months, psychological characteristics of a stimulus become important to infants. • Eg., familiarity and novelty • Kagan (1971) proposed that at 2 months, infants form schemas. • Sensory representations of a stimulus. • The similarity of a stimulus to a previously determined stimulus will determine attention.

24. Psychological Stimulus Characteristics • Infants are most attentive to stimuli that are moderately discrepant from a schema. • Discrepancy principle. • They are less attentive to stimuli that are highly familiar, or highly discrepant. • McCall et al. (1977) familiarized 2-4 month-old infants to stimuli and later showed them stimuli that varied in their similarity with the original.

25. Psychological Stimulus Characteristics • Stimuli that were highly similar, or highly discrepant to the original received less attention than those that were moderately similar or moderately discrepant. • There are instances when infants prefer similar, not novel, stimuli.

26. Psychological Stimulus Characteristics • Generally, young infants prefer familiar stimuli, then show no preference, then they prefer novel stimuli. • Takes time to create schemas.

27. The Development of Face Processing • Infants prefer vertical, symmetrical stimuli with curved lines making them well-suited to attend to faces. • A bias to human faces would make evolutionary sense and would facilitate attachment. • Johnson et al. (1991) showed newborns paddle stimuli which resembled faces, did not resemble faces, or were blank.

28. The Development of Face Processing • They presented these stimuli and moved them. • Measured how much infants followed the stimuli by moving their eyes and head. • Following this paradigm, infants will show a preference for face-like stimuli as early as 5 days of age.

29. The Development of Face Processing • There is evidence that newborns may be able to make discriminations between faces. • Look longer at photos of their mothers than at photos of other women (Bushnell et al., 1989) . • They will alter sucking rate to see a photo of their mother over another woman (Walton et al., 1992). • Babies also show a preference for attractive faces over unattractive faces (Langlois, 1987). • Infants as young as two months will look longer at attractive faces as opposed to unattractive faces.

30. The Development of Face Processing • This might be because infants prefer upright, curvilinear, symmetrical stimuli. • It might be evolutionary since symmetry is a sign of health. • Important for mate selection.

31. Auditory Development • Hearing develops substantially in the first year, but is not adultlike until about 10 years of age. • Auditory perception is well-developed in the newborns, particularly at high frequencies. • DeCasper and Fifer (1980) found that 1- to 3-day-old infants will alter their sucking rates to hear a tape recording of their mothers as opposed to that of a stranger.

32. Auditory Development • DeCasper’s and Spence’s (1986) earlier research on infants and sucking rate shows that they’re capable of auditory learning prenatally. • Studies measuring heart rate in response to familiar and novel passages during the third trimester reveals similar findings.

33. Speech Perception • Infants can perceive most and perhaps all phonemes found in all human languages. • Phonemes: the basic units of speech. • Eimas et al. (1971) repeatedly presented 1-month-olds with a phoneme along the ba/pa continuum until they showed a decrease in sucking rate (i.e., habituation).

34. Speech Perception • Infants would show an increase in sucking rate (dishabituate) if a phoneme was presented on the other side of the ba/pa continuum. • They use the same dividing line as older children and adults.

35. Speech Perception • Infants can make phoneme discriminations that adults can not make. • They can make discriminations in foreign languages that adults can not make. • However, this ability is quickly lost. • At the same time, they are able to make increasingly fine discriminations between phonemes in their mother tongue (Kuhl et al., 2006).

36. Speech Perception • This language flexibility is probably not adaptive after a certain age. • The brain should dedicate neurons to processing sounds in the language its exposed to. • Infants are able to recognize frequently heard sound patterns at least by 4.5 months of age.

37. Violation-of-Expectation Method • An infant’s reaction to an unexpected event is used to infer what he/she knows. • Uses infants’ looking behavior along with preference-for-novelty and habituation/dishabituation procedures. • If what they see differs from what they expect, they should look longer at this event.

38. Core Knowledge • Infants possess core knowledge. • They are born with a small set of distinct systems of knowledge that have been shaped by natural selection and upon which new skills and belief systems are built. • According to Spelke, there are three core knowledge systems in infancy. • Object representation, knowledge of people and actions, ability to represent numbers or quantities.

39. Object Representation • What infants know about the nature of objects. • Object Constancy: Knowledge that an object remains the same despite changes in how it is viewed. • As an object gets closer, its retinal image gets larger • We perceive it as getting “closer” rather than “larger” • Newborns possess object constancy (Slater, Mattock, & Brown, 1990). • Infants were habituated to an object of a particular size.

40. Object Constancy • Then shown one of two objects. • Same object as seen at a different distance • New object of a different size (yet retinal image is the same). • Infants remain habituated to the first object

41. Object Continuity and Cohesion • Individual objects are seen as cohesive wholes with distinct boundaries. • Kellman and Spelke (1983) tested this with 4 month-olds. • Habituated to a stick moving back and forth underneath a bar • Tested with one stick or two stick displays

42. Condition 1Habituation + 2 Object Test

43. Condition 1Habituation + 2 Object Test

44. Condition 1Habituation + 2 Object Test Condition 2Habituation + 1 Object Test

45. Condition 1Habituation + 2 Object Test Condition 2Habituation + 1 Object Test Don’t recover (dishabituate): expected Recover (dishabituate): unexpected

46. Object Continuity and Cohesion • 4-mo dishabituate to condition 1 but not condition 2 • But only if the object was moving • Not if stationary • 2- and 4-month-olds infer object unity in some situations, but not in others. • Newborns don’t appear to be born with continuation.

47. Objects Continuity and Cohesion • Baillargeon et al. (1995) investigated whether infants understood the notion of support.

48. Objects Continuity and Cohesion • 3-month-old infants weren’t surprised with the impossible outcome. • 6.5-month-olds expect the box to fall unless a large portion maintains contact with the platform.

49. Objects Continuity and Cohesion • Initially, infants believe that any contact between two objects is enough for one to support the other. • They progress until they reach an adult-like concept of support. • However, 2-year-old children will fail on a similar task (see Hood et al., 2000; p. 215).

50. Objects Continuity and Cohesion • Baillargeon proposed that infants possess the principle of persistence. • Objects exist continuously, remain cohesive, and retain their individual properties. • Yet this notion is underdeveloped at first, and later becomes enriched with experience.