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Perceptual Development

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1 Perceptual Development
Chapter 5 OBJECTIVES: What senses do newborn babies have? Do their senses work like adults? How do Infants perceive the world?

2 The Senses begin to function early in life
The Senses begin to function early in life. But how can we actually know what an infant senses? Since infants can’t tell us, researchers have devised ways to find out.

3 Sensation To understand what an infant can sense researchers often present two stimuli and record the baby’s response. For example a baby is given a sweet tasting substance and a sour tasting substance If the baby consistently responds differently to the two stimuli then the infant must be able to distinguish between them.

4 A technique called Habituation is often used in researching infant preference
This is the process of getting used to something. Click on the baby to view a video clip (also provided in your textbook DVD)

5 Can infants use their senses like adults?
NO, we do not arrive with all of our senses fully functioning. This is yet another area that will develop and mature with the infant.

6 Smell Infants have a keen sense of smell and respond positively to pleasant smells and negatively to unpleasant smells (Menella, 1997). Honey, vanilla, strawberry, or chocolate: relaxed, produces a contented-looking facial expression Rotten eggs, fish, or ammonia produce exactly what you might expect…infants frown, grimace or turn away Newborns can differentiate salty, sour, bitter, and sweet: Infants prefer sweet  infants will nurse more after their mother has consumed a sweet-tasting substance like vanilla Newborns prefer sweet. However, at 4 months, infants will have a salty preference – they will start liking salt which was aversive to them as newborns.

7 Did you know… Young infants recognize familiar odors
Newborns will turn toward of a pad that is: Saturated with their own amniotic fluid Saturated with their own mother’s milk or her perfume (Porter & Winburg, 1999). Isn’t that amazing?

8 Taste Newborns also have a highly developed sense of taste. They can differentiate salty, sour, bitter & sweet tastes (Rosenstein, 1997). Do you think infant’s have a favorite taste?

9 Taste Most infants seem to have a “sweet tooth”.
Infants will nurse more after their mother has consumed a sweet-tasting substance like vanilla (Menalla, 1997) Newborns prefer sweet. However, at 4 months, infants will have a salty preference They will start liking salt which was aversive to them as newborns.

10 Touch Newborns are sensitive to touch, many areas of the newborn’s body respond reflexively when touched What do YOU think? If babies react to touch, do they experience pain? Babies behavior in response to a pain-provoking stimulus suggest that they experience pain Pain expression: Lowering of eyebrows Pursing of lips Opening mouth to cry Showing signs of agitation – moving arms, hands, and legs

11 OUCH!? The infant’s nervous system is definitely capable of experiencing pain Receptors for pain in the skin are just as plentiful in infants as they are in adults. Babies behavior in response to a pain-provoking stimulus suggests that they experience pain.

12 What Do Infants See? Vision is the least mature of all the senses at birth because the fetus has nothing to look at, so visual connections in the brain can’t form until birth. Lack of visual acuity is due to the lack of cone development Acuity improves as cones elongate and migrate – they move closer together to form the fovea

13 Newborn visual acuity is 20/400 to 20/800
20/200 or worse defines legal blindness in adults By 6 months, infant visual acuity is 20/25 By 1 year, infant visual acuity is at adult levels (20/20) Click on the baby to see like an infant!

14 What is the clarity of infant vision and how can we measure it?
Visual acuity is defined as the smallest pattern that can distinguished dependably. Infants prefer to look at patterned stimuli instead of plain, non-patterned stimuli To estimate an infant’s visual acuity, we pair gray squares with squares that differ in the width of their stripes. By measuring the width of the stripes and their distance from the infant’s eyes, we can estimate acuity – being able to detect thinner stripes indicates better acuity

15 When the infant looks at the two stimuli equally long, it indicates they are no longer able to distinguish the stripes of the patterned stimulus from the solid gray square There comes a point at which the black and white stripes become so fine that they simple blend together and appear gray – just like the solid gray pattern

16 As for acuity: The improvements in contrast sensitivity is due to the elongation and tighter packing of cones in the retina and is associated with development of the visual cortex Improving contrast sensitivity: This picture provides a gray scale representation of how an infant might see contrast information at 3, 6, and 9 months compared to an adult. The infant is increasingly able to see fine detail, low contrast elements in their environment At birth, infants’ sensitivity to fine, high-spatial frequency gratings, like their acuity, is very poor but improves steadily with age.

17 Light Sensitivity Newborns begin to see the world not only with greater acuity but also in color At birth, infants have the greatest sensitivity to intermediate wavelengths (yellow/green) and less to short (blue/violet) or long (red/orange).

18 Newborns can perceive few colors, but By 3-4 months newborns are able to see the full range of colors (Kellman, 1998). In fact, by 3-4 months infants have color perception similar to adults (Adams, 1995).

19 At 1 week, the infant can discriminate the desaturated red from gray
At 2 months, the infant can discriminate the desaturated blue from gray At 1 week, the infant is likely to perceive the desaturated red to be different from the gray. However, a difference between the desaturated blue and the gray is not likely to be perceived until about 2 months

20 What do babies hear? Hearing is the most mature sense at birth. In fact, some sounds trigger reflexes even without conscious perception. The fetus most likely heard these sounds in the womb during last trimester Sudden sounds startle babies-making them cry, some rhythmic sounds, like a heartbeat/lullaby put a baby to sleep. Yes, infants in first days of life, turn their head toward source of sounds and they can distinguish voices, language, and rhythm.

21 Auditory Threshold The fetus can hear in utero at 7-8 months, so it is no surprise that newborns respond to auditory stimuli but, do infants hear as well as adults?? No they cannot. The Auditory threshold refers to the quietest sound that a person can hear. The quietest sound an newborn responds to is about 4 times louder than the quietest sound an adult responds to. Hearing is not at adult levels until 5-8 years of age Signs of hearing impairment: Infant never responds to sudden, loud sounds Infant has repeated ear infections Infant does not turn head in direction of sounds by 4-5 months Infant does not respond to his/her own name by 8-9 months Infant does not imitate speech sounds and simple words by 12 months

22 Do infants hear like adults?
Research reveals that adults hear better than infants because adults can hear some very quiet sounds that infants cannot. Research shows that infants hear sounds best that have high pitches in the range of human speech (Jusczyk, 1995). Can differentiate vowels from consonants At 4 months, can recognize own name Infants also use sound to locate objects and estimate distance.

23 How DO Infants Perceive the World?

24 Perceptual Constancies
An important part of perceiving objects is that the same object can look very different Infants master size constancy very early on They recognize that an object remains the same size despite its distance from the observer

25 You can recognize that the woman in this picture has not shrunk…she is just farther away

26 Depth Perception Infants are not born with depth perception, it must develop. The images on the back of our eyes are flat and 2-dimensional To create a 3-D view of the world, the brain combines information from the separate images of the two eyes, retinal disparity Visual experience along with development in the brain lead to the emergence of binocular depth perception around 3-5 months of age

27 Perception in infants Can infants process sensory information accurately? This was a question posed by Walk and Gibson in 1960 The Visual cliff experiment was designed to provide the illusion of a sudden drop off between one horizontal surface and another

28 Face Recognition Infants enjoy looking at faces, a preference that may reflect innate attraction to faces, or a fact that faces may attract infant’s attention. At birth, infants are attracted to the borders of objects When looking at a human face a newborn will pay more attention to the hairline or the edge of the face (even though the newborn can see the features of the face)

29 By 2 months of age, infants begin to attend to the internal features of the face – such as the nose and mouth By 3 months of age, infants focus almost entirely on the interior of the face, particularly on the eyes and lips. At this age, infants can tell the difference between mother’s face and a stranger’s face. Theorist’s believe that infants are attracted to human faces because faces have stimuli that move (eyes and lips) and stimuli with dark and light contrast (the eyes, lips and teeth).

30 Infants readily look at faces, a preference that may reflect an innate attraction to faces or the fact that faces have many properties that attract infant’s attention

31 Perceiving Faces Infants are particularly interested in looking at human faces, but focus on different areas of the face depending on their age

32 Motor Development

33 Test your Knowledge At what age can at least 50% of children begin to display each of these behaviors? Pedal a tricycle Sit without support Walk unassisted Stand on one foot for 10 seconds Roll over Kick a ball forward Crawl 2 years (90% by 3 years) 5-6 months (90% by 7-8 months) 11-12 months (90% by months) 4.5 years 3 months (90% by 5 months) 20 months (90% by 2.5 years) 7 months (90% by 9 months)

34 How Did You Do? Roll over 3 months, 90% by 5 months.
Pedal a tricycle 2 years, 90% by 3years Sit without support 6 Months, 90% by 7-8 months. Walk unassisted 12 Months, 90% by 14 months. Stand on one foot for 10 seconds 4 ½ years Roll over 3 months, 90% by 5 months. Kick a ball forward 20 months, 90% by 9 months. Crawl 7 months, 90% by 9 months

35 Motor Milestones 50 percent 90 percent Roll over 3.2 months 5.4 months
Grasp rattle 3.3 months 3.9 months Sit without support 5.9 months 6.8 months Stand holding on 7.2 months 8.5 months Pincer grasp 8.2 months 10.2 months Crawl 7.0 months 9.0 months Stand alone 11.5 months 13.7 months Walks well 12.3 months 14.9 months Build tower (2 cubes) 14.8 months 20.6 months Walk steps 16.6 months 21.6 months Jump in place 23.8 months 2.4 years Copy circle 3.4 years 4.0 years Rolls from side to back – average at 2 months, 90% at 5 months Rolls from back to side – average at 4.5 months, 90% 7 months Pulls to stand – average at 8 months, 90% as 12 months Walks on tiptoe – average at 25 months, 90% at 30 months

36 Head Control At birth infants can turn their heads from side to side while lying on their backs By 2-3 months they can lift their heads while lying on their stomachs By 4 months infants can keep heads erect while being held or supported in a sitting position Hold chin up while on stomach: around 1 month Hold chest up while on stomach: around 2 months

37 Before you walk, you must learn to….
At around 6-8 months, infants become capable of self-locomotion To master walking (around months), infants must acquire distinct skills Standing upright Maintaining balance Stepping alternately Using perceptual information to evaluate surfaces

38 Crawling Begins as belly-crawling
The “inchworm belly-flop” style Most belly crawlers then shift to hands-and-knees, or in some cases, hands-and-feet Some infants will adopt a different style of locomotion in place of crawling such as bottom-shuffling while some infants skip crawling altogether Due to the “back-to-sleep” movement, infants spend less time on their tummies which may limit their opportunity to learn how to propel themselves Start around 6 months: Over the next couple months, the infant learns to move confidently from the sitting position to being on all fours The infant realizes that he/she can rock back Around 9-10 months: Pushing off with knees gives the boost needed to get mobile With practice, the infant will learn to go from sitting to crawling With practice, infant will learn “cross-crawling” – moving opposite hand and leg rather than arm and leg from same side of the body By 12 months – competent crawler

39 Belly-crawling Hands-and-knees crawling Hands-and-feet crawling

40 Walking – Stepping Children do not step spontaneously until approximately 10 months because they must be able to stand in order to step Maintaining balance when transferring weight from foot to foot seems to be key Thelen and Ulrich (1991) found that 6- and 7-month-olds, if held upright by an adult, could demonstrate the mature pattern of walking of alternating steps on a treadmill Called a toddler around months: stands alone and can “toddle”

41 Gross motor skills Emerge directly from reflexes.
These are physical abilities involving large body movements and large muscle groups such as walking and jumping. Involve the movement of the entire body- Rolling over, standing, walking climbing, running

42 Fine Motor Skills After infancy fine motor skills progress rapidly and older children become more dexterous because these movements involve the use of small muscle groups These consist of small body movements, especially of the hands and fingers. such as drawing, writing your name, picking up a coin, buttoning or zipping a coat.

43 Handedness Young babies reach for objects without a preference for one hand over the other The preference for one hand over the other becomes stronger and more consistent during preschool years By the time children are ready to enter kindergarten, handedness is well established and very difficult to reverse Handedness is determined by heredity and environmental factors Approximately 10% of children write left-handed Two right-handed parents will have right-hand children. If a parent is left-hand then there is a possibility for a left-handed child Culture: School desks, scissors, and can openers are designed for right-handed people Islam religion dictates that the left hand is unclean – the religion forbids people from using their left hand to eat or to greet others Writing with the left hand is cultural taboo in China

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