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See Ch5 for info on object knowledge, illustrative examples, smell and taste
Infant Research Designs
Preferential Looking Paradigms
Method for studying visual attention in infants ● Since we cannot ask questions, we use implicit measures The two items/patterns/faces are presented to the infant at the same time: ● Measure the looking time at each item ● Longer looking time at one item indicates: a. Infant can discriminate between the items b. Infant has a preference for one of the items (assumed ● This can be coded manually (frame by frame) or using eye tracking technology Ex. If a baby looks longer at a regular human face, rather than one with scrambled up features, we can infer that they are more drawn to the human face/prefer it. ● Doesn’t prove a preference in the same what that you would ask an adult straight up ● Eye tracking can catch where and how long the infant is attending to the stimulus, can narrow down what about the stimuli the infant is focusing on
Habituation Paradigms
Babies getting bored = habituation ● Ex if they see something that’s very close to the original stimulation they will still get bored ● Allows us to see if infants can differentiate between different types of categories ● Can also tell us about subtle differentiation, such as shades of color ● If it piques their interest, it shows the baby can discriminate ● Also helpful in speech research, can tell if baby can discriminate between different types of sound ("d" in mud vs. "dg" in judge) ● Habituation shows us how the baby's memory is functioning (habituation = baby remembering stimulus and getting bored)
Vision and Perception
(General Info, Visual Scanning, Face Perception, Object and Depth Processing)
Read Ch. 5 for more info on: Object knowledge; illustrative examples; smell & taste ● Sensation – detecting and processing of basic information in the environment/external world ○ Sensory organs (eyes, ears, tongue, nose, hands) will pick up signals (sounds, chemicals, electric waves) and these will travel and be sent to the brain ○ Input stage, detecting ○ Ex. Light hitting the retina ● Perception – how we organize, interpret, and make sense of this incoming information ○ Builds subjective understanding and mental representations of the world
○ Once the brain has the info, it assigns meaning to the raw information ○ Ex. Seeing the tree vs recognizing the tree ○ Making sense of what we are detecting
Vision in Infancy
● Initially, infants very poor vision (20/120 vision) ○ Immature cone cells only catch 2% of light ○ Cone cells in retina responsible for detecting fine details and color are quite immature ● Low Visual Acuity ○ Infants see the world as blurry and low contrast in the first couple weeks ○ Sharpness of visual discrimination ● Poor Contrast Sensitivity ○ They can see black and white (contrast), and general shapes, but no fine details ○ Struggle to detect subtle differences in light and dark areas in a visual pattern ○ Ex. Infant toys are bright contrast and simple detail ○ Cant sense a light gray on a dark gray background – can't tell difference, looks the same ● Adult-like vision at around 8 months ○ Clear vision allows you to interact with the world, and get milestones ○ Coordinates eye movements, recognizes caregiver Testing Visual Acuity ● Take two paddles and show them to the infant side by side, ● Decreases the thickness of strikes until its similar to the solid paddle ○ Makes it increasingly lower contrast ● This can tell us where their visual acuity is at
Colour Perception in Infancy
First month: ● Infants can only see shades of muted tones in the first month Two months: ● Vision is almost identical to that of adults – can see full spectrum of colors Do infants represent colors in categories even before they learn language? ● Kind of ● Harder time within category distinctions ● Can distinguish between categories Five months: ● Evidence of categorical discrimination ○ Brain responds differently to shifts between categories (green --> blue) ○ No evidence within category (light --> dark blue)
Habituation Paradigms
Babies raised in homogenous race homes are better at discriminating own race ● Babies raised in racially diverse homes can discriminate equally well between the races they are frequently exposed to ● This is the Other Race Effect (ORE) Early experiences shape perceptual abilities and prepares us for the environment we will be in ● We become good at perceiving the stimuli that is the best for us or we are more familiar with ● We become so specialized that we become worse at perceiving stimuli that we are not familiar with
Object Perception
Even though what we see is changing every second, we perceive the world to be stable ● Perceptual constancy – perception that objects are constant in size, shape, color, properties despite the retinal image (what you perceive) changing ○ ex. A water bottle looking the same regardless of the position it is in or you are in ○ Even though the image on the retina may change, we can perceive it maintains the true size ○ The ability does not depend heavily on experience, suggesting it is at least partially innate or hardwired ○ Understands that something remains the same size even if the size is changing in your retina
Cube Study and Object Segregation:
● 2 cubes – cube A (small) is shown to the baby over and over ● Then they would put cube A close to the baby on a board and then take cube B (larger) and put it further away ● On the retina, they appear to be the same size ● If babies only cared about the image on the retina, babies would perceive no difference in sizing ● What they found was babies would look longer at cube b (larger) They could detect real world size and they could understand that physically in the real world, cube B is bigger
Object Segregation
● Infants would see a box and a rod and then would show the rod moving being the rod ● They would then present a full rod and a broken rod ● The baby looked more at the broken rod, as they were most surprised since they assumed the full rod was behind the box
● They would repeat this, but now showing the rod moving in 2 pieces. This time the baby looked more at the full rod. ● Used common movement (physical or visual cues) to help them understand the object segregation ● If something moves together, they assume it is one thing
Infants using cues of physics and gravity to influence their view of object segregation ● Could be 2 objects (both resting on the ground), must be 1 object because tube cannot suspend itself in the air
Depth Perception
Need to interpret a 2D retinal image as a 3D representation of the world ● One month old – blinks when an object appears to be coming towards their face ○ Optical expansion – cue in which an approaching object occludes increasing more of its background ● Four month old – brain uses the difference between the image of an object in each eye to calculate depth ○ Binocular disparity ● Seven month old – uses monocular (one eye) depth cues ○ Relative size, interposition, texture gradient ● Very young children show sensitivity to depth ● Optical expansion, we sense something is coming closer to us
Motor development Main 6 neonatal reflexes ● Some are more automatic in babies, but some may be used more if they are hungry or want to communicate (ex. rooting: opening mouth and turning head in direction of touch) ● Most are developmental (ex. Sucking, startling), but some researchers don’t know why they occur (ex. Tonic neck)
● Around 2-5 months, infants will support once they are stationary and prone (front facing) ● 4-10 months, sitting and standing with support ● 9.5-14 months, standing and walking independently ● Motor milestones are not universal! ○ They vary significantly as a function of individual experiences, often due to culture, parental practices that can encourage or hinder development ○ In some cultures, caregivers will engage infants in stretching and massages – thought it strengthen coordination and muscles ■ Walk and stand at an early rate ■ 92% sit on their own at 5 months (cameroon) ○ In Western culture – parents use supportive devices so they are not using all their muscles ■ 17% sit on their own at 5 months in USA, 0% in Italy ○ Voluntary reaching seems to play the biggest role in infant development – infant motivation
Gross motor skills involve large muscle movements
● Walking, running, and jumping Fine motor skills require small, precise movements from small muscles, such as those in the fingers and hands ● Reaching, grasping ● Writing, buttoning clothes, and manipulating small objects The difference is the groups of muscles used
Psychology is WEIRD ● No representative of the whole world and are often outliers due to all the resources they can benefit from ● Findings based on WEIRD samples are thought to be universal ● Ex. Visual illusions: people who are raised industrialized settings are more susceptible to the Mueller illusions ● Moral reasoning – fairness, punishment will vary depending on culture, government ● Attachment, motor and social skills can look very different Western Educated Industrialized Rich Democratic
Learning through Action
Evolving Views of Motor Development ● Early pioneers' perspective: brain maturation is key ● Current Theorists' viewpoint: Both environment and experience and interactions play a critical role ○ Environment is also important ● Factors influencing motor development are varied: ○ Improving strength, posture control, balance, body proportions, motivations ● Discovery of affordances – the possible actions "afforded" by an object or situation ○ Ex. Small objects allow the child to practice grasping reflex ○ Flat dry surfaces afford infants learning to walk to practice doing so
Integrating Perception and Action Big challenge: learn the boundaries of what can and cannot do with their bodies Ex. ○ Visual cliff experiment – shows that individuals need to relearn how to use visual depth perception every time they use a new skill (crawling, cruising, walking, etc.)
Integration Error ● Scale Errors: when children attempt to do something with an object that is much too small for them ● Grasp Errors: infants will try to pick up an object that is 2D, like a photo in a book
● Mirror neurons fire when observing someone else does an action the same as they would if you were completing the action
Statistical Learning Detecting regularities in the environment ● What will happen based on my past experiences
Characteristics of Statistical Learning: ● Fast ● Incidental ● Effortless ● Instinctive Can pick up on these skills without being explicitly told
Two month old infants show surprise when infrequently paired items are shown in sequences
As we discussed in Chapter 4, Piaget believed that young infants’ understanding of the world is hindered by their inability to think about anything that they cannot currently see, hear, touch, or otherwise experience. Piaget based his theory in part on his tests of object permanence, which led him to infer that when an infant fails to search for an object that has disappeared from sight, it is because the object has also disappeared from the infant’s mind. However, as also noted in Chapter 4, skepticism gradually arose about Piaget’s explanation of this fascinating phenomenon. Clever studies since Piaget’s time have established that out of sight is not out of mind, even for young infants.
Darkness provides a real-world situation in which infants might need to remember objects that they cannot see. And indeed, when young infants are shown an attractive object and the room is then plunged into darkness, they reach to where they last saw the object, indicating that they expect it to still be there (Perris & Clifton, 1988; Stack et al., 1989). Young infants even represent the size of objects they cannot see. In one study, when 6-month-olds sitting in the dark heard the sound of a familiar large object, they reached towards it with both hands; but they reached with only one hand when the sound was that of a familiar small object (Clifton et al., 1991).
Other studies have used the violation-of-expectancy procedure to study infants’ object knowledge. The logic behind this method is that if infants observe an event that is inconsistent with what they know about the world, they will be surprised—or at least interested. Thus, an unexpected event should evoke a greater response (such as longer looking or a change in heart rate) than an unsurprising event. The violation-of-expectancy technique was first used in a classic series of studies investigating infants’ representations of non-visible objects (Baillargeon, Spelke, & Wasserman, 1985). Infants were habituated to the sight of a solid screen rotating back and forth through a 180-degree arc (see Figure 5.6). Then a box was placed in the screen’s path, and the infants saw two test events. In the possible event, the screen rotated upwards, occluding the box as it did so, and stopped when it contacted the box. In the impossible event, the screen continued to rotate a full 180 degrees, appearing to pass through the space occupied by the box.
As you learned in Chapter 2, sensitivity to taste and smell develops before birth. Infants vary in the flavours they are exposed to early in life as a function of maternal diet (if they are breast-fed) and choice of formula (if they are formula-fed). Those early experiences can have long-lasting consequences. Early exposure to bitter flavours—before the age of 6 months—increases the likelihood of a later preference for those flavours (Nehring et al., 2015). However, data regarding the long-term effects of early exposure to sweet and salty flavours are mixed, with some studies showing effects and others not. The timing of early exposure can also influence later taste preferences. For example, prenatal exposure to garlic increased children’s intake of garlic-flavoured foods at age 8 to 9 years, whereas exposure to garlic in breast milk did not predict children’s later preferences for garlic flavours. Preferences for smells are also present very early in life. Smell plays a powerful role in how a variety of infant mammals learn to recognize their mothers. It probably does the same for humans, as shown by studies in which infants chose between the scent of their own mother and that of another woman. In one such study, a pad that an infant’s mother had worn next to her armpit was placed on one side of the infant’s head and a pad worn by a different woman was placed on the other side. Two-day-old infants spent almost twice as long oriented to the pad infused with their mother’s unique scent (Marin, Rapisardi, & Tani, 2015). Newborns outfitted with a specially adapted skateboardlike device called a Crawliskate®, which they can use to propel themselves on their stomachs, will crawl farther in response to the smell of their mother’s breast odour compared to a control odour (Hym et al., 2021).
Smell and taste are an important component of the nutritional behaviours discussed in Chapter 3. One such behaviour is food neophobia, wherein children avoid unfamiliar foods. Researchers were interested in whether individual differences in the strength of toddlers’ reactions to different tastes and smells could explain their degree of food neophobia (Monnery-Patris et al., 2015). Interestingly, toddlers’ degree of reactivity to food odours, but not food tastes, predicted their degree of food neophobia. Thus, children’s negative reaction to novel foods may
be more strongly influenced by smell than by taste—a result that is consistent with many parents’ frustration that their children regularly reject new foods before tasting them.
