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HUMAN DEVELOPMENT 1 PSYCHOLOGY 3050: Infant Perception and Cognition Ch 4 Dr. Jamie Drover SN-3094, – Winter Semester, 2015
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.
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).
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).
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.
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.
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.
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.
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.
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.
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.
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
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.
Testing Infants’ Visual Acuity The thinnest stripewidth at which the observer can determine the location of the stripes provides a measure of visual acuity.
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).
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 Infants prefer high contrast stimuli over low contrast stimuli. –See Salapatek and Kessen (1966) p. 193.
The Development of Visual Preferences
Infants at 1 month of age focus their attention primarily on the outside of a figure. Externality effect.
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.
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.
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.
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.
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.
Psychological Stimulus Characteristics Generally, young infants prefer familiar stimuli, then show no preference, then they prefer novel stimuli. Takes time to create schemas.
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.
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.
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.
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.
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.
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.
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).
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.
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).
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.
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.
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.
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.
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
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
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.
Objects Continuity and Cohesion Baillargeon et al. (1995) investigated whether infants understood the notion of support.
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.
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).
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.
Objects Continuity and Cohesion Hood et al. (2000) study with 2- and 2.5-yr-olds (a) (b) (c) Familiarize: Test event: Where is The ball?
Objects are Continuous, Solid, and Require Support Perhaps the difference in the nature of the tasks explain these findings. That is, 2-year-olds need to demonstrate an explicit understanding of spatial relations, whereas infants need only display an implicit understanding.
Object Permanence The understanding that objects continue to exist when they can not be perceived. According to Piaget, until 4 months of age objects exist merely as extensions of their perceptions or actions upon them. At 4 months, they will retrieve an object that is partly hidden. –Will not search for a completely hidden toy.
Object Permanence At 8 months, infants will retrieve a completely hidden toy. Yet, they can not solve the A not B task. At 12 months, they can solve A not B, but cannot do invisible displacement. –Object is hidden in one container and then in another container out of the vision of the observer. –Need to mentally represent objects.
A New Look at Object Permanence Infants as young as 3.5 months possess more knowledge than Piaget proposed. –Some believe object permanence is innate. Baillargeon (1987) studied this using the violation-of- expectation method (p 140) and 4.5-month-old infants were habituated to a screen moving 180° in space. A block was then placed behind the screen to produce an impossible event.
A New Look at Object Permanence
No differences were found for the control condition. In the experimental condition, infants looked longer at the impossible event. They believed the block continued to exist when out of their sight and were surprised when the screen dropped. They have knowledge of object permanence and that one solid can’t pass through another.
A New Look at Object Permanence Newcombe et al. (1999) buried a toy in a sandbox in front of 5-month-olds, and then dug it out 10 sec later. After multiple trials, the object was dug out from 6 inches away. Infants looked significantly longer at these trick trials. They weren’t surprised when a different object was dug out of this location.
A New Look at Object Permanence Even when using the traditional A not B task, infants as young as 7.5 months will search correctly on B trials. –The delay must be short. –Thus, inhibition is likely involved.
Early Number Concepts Numerosity: the ability to determine the number of items in a set without counting. Ordinality: a basic understanding of more than or less than. Infants as young as 10 months can distinguish between two boxes containing different amounts of crackers.
Early Number Concepts Infants as young as 6 months of age can tell the difference between arrays, but the ratio must be relatively large.
Simple Arithmetic Wynn has used the violation-of- expectations method to show that infants can add and subtract small quantities.
But, it’s not clear exactly what’s going on here. Maybe infants are not responding to number, but the total amount of substance present.
Arguments Against Core Knowledge Bogartz et al (1998) argue that it is not necessary to use innate knowledge of objects to explain infants’ looking behavior. Infants acquire object knowledge through perceptual experience.
Arguments Against Core Knowledge This perceptual processing produces the looking patterns others interpret as innate knowledge. Perceptual processing takes time. Novel events (impossible events) simply take longer to process because initial encoding of the stimuli needs to be done. This takes time and results in longer looking times.
Category Representation Babies show preferences indicating that they have some form of visual memory. This implies that they form categories. Items from similar categories are treated as being the same.
Measuring Categorization Often measured using habituation/dishabituation. Stimuli are varied slightly during habituation trials. Eg., when habituating infants to faces, multiple faces can be used. –Infants will still show decrease in looking times. Cohen and Strauss (1979) did this with 30-week-olds. –Infants can form a human face category. –Human face is distinct from other perceptual categories.
Measuring Categorization Infants as young as 3 months can form categories (see Eimas and Quinn, pp 147-8). But do these categories exist when infants enter the lab? Or can infants merely distinguish the physical features necessary to discover the categories in the experimenters’ minds? –It’s probably a little of both.
The Structure of Infants Categories Category Prototype: An abstract representation of a category. A best example of a category. Infants appear to form category prototypes –See Roberts and Horowitz, p 149. –Infants will form a category for the concept of birds when habituated to highly typical exemplars. –The same is not the case when atypical exemplars are used.