Body Growth Height increases 50% by age 1, 75% by age 2 Weight doubles by 5 months, triples by 1 year Individual and group differences in size and rate of growth © Monkey Business Images/Shutterstock

Body Growth During First Two Years Figure 4.1 Body growth during the first two years Figure 4.1

Individual and Group Differences in Growth male/female ethnic Individual differences Skeletal age: best estimate of physical maturity © Oksana Kuzmina/Shutterstock

Changes in Body Proportions Growth Trends Changes in Body Proportions Cephalocaudal “Head to tail” Lower part of body grows later than the head Proximodistal “Near to far” Extremities grow later than head, chest, and trunk

Neurons and Their Connective Fibers Nerve cells that store and transmit information Synapses Tiny gaps where fibers from different neurons come together but do not touch Neurotransmitters Chemicals that are released by neurons and cross the synapse Figure 4.2

Methods for Measuring Brain Functioning Electroencephalogram (EEG) Event-related potentials (ERPs) Functional magnetic resonance imaging (fMRI) Positron emission tomography (PET) Near-infrared spectroscopy (NIRS)

Regions of the Cerebral Cortex Figure 4.4 The left side of the human brain, showing the cerebral cortex Figure 4.4

Prefrontal Cortex Region of the cerebral cortex responsible for thought, especially: consciousness inhibition of impulses integration of information use of memory, reasoning, planning, and problem-solving strategies Undergoes rapid growth in the preschool and school years, and in adolescence

Lateralization of the Cerebral Cortex Left Hemisphere Verbal abilities Positive emotion Sequential, analytic processing Right Hemisphere Spatial abilities Negative emotion Holistic, integrative processing

Brain Plasticity At birth, hemispheres have already begun to specialize Highly plastic cerebral cortex has high capacity for learning If part of cortex is damaged, other areas can take over its tasks Older children and adults retain some plasticity, but less than in young children

Sensitive Periods in Brain Development Appropriate stimulation is vital for brain growth Experience-expectant growth: depends on ordinary experiences Experience-dependent growth: additional growth resulting from specific learning experiences © Andy Lim/Shutterstock

Changing States of Arousal Sleep–wake pattern moves to night–day schedule during first year By age 2, total sleep time declines from 18 to 12 hours per day Sleep patterns are affected by social environment, cultural values © Michael Pettigrew/Shutterstock

Influences on Early Growth Heredity Nutrition: breastfeeding vs. bottle-feeding risks of overfeeding Malnutrition © stefanolunardi/Shutterstock

Benefits of Breastfeeding Correct balance of fat and protein Ensures nutritional completeness Helps ensure healthy physical growth Protects against disease © Pixel Memoirs/Shutterstock

Malnutrition Type Consequences Marasmus (diet low in all essential nutrients) Lasting physical damage; learning and behavioral effects; risk of death Kwashiorkor (diet very low in protein) Lasting physical damage; learning and behavioral effects Food insecurity Effects on physical growth; learning problems

The Steps of Classical Conditioning Figure 4.5 The steps of classical conditioning Figure 4.5

Operant Conditioning Reinforcer Punishment Increases probability that behavior will occur again by presenting desirable stimulus removing unpleasant stimulus Punishment Reduces probability that behavior will occur again by presenting unpleasant stimulus removing desirable stimulus

Using Habituation to Study Infant Memory and Knowledge Figure 4.6 Using habituation to study infant perception and cognition Figure 4.6

Imitation Infants are born with primitive ability to imitate Mirror neurons provide biological explanation Powerful means of learning © Seleznev Oleg/Shutterstock

Motor Development Sequence and Trends Gross-motor development: crawling, standing, walking Fine-motor development: reaching, grasping Sequence is fairly uniform Large individual differences in rate of motor progress © S.Borisov/Shutterstock

Motor Skills as Dynamic Systems Mastery involves acquiring increasingly complex systems of action with each skill Each new skill is joint product of central nervous system development the body’s movement capacity the child’s goals environmental supports for the skill

Cultural Variations in Motor Development Rates and patterns of development affected by early movement opportunities environmental stimulation child-rearing practices © XiXinXing/Shutterstock

Milestones of Reaching and Grasping Prereaching Ulnar grasp Transferring object from hand to hand Pincer grasp © StockLite/Shutterstock

Developments in Hearing 4–7 months Sense of musical phrasing 6–7 months Distinguishes musical tunes based on variations in rhythmic patterns 6–8 months “Screens out” sounds not used in native language 6–12 months Detects sound regularities in human speech 7–9 months Begins to divide speech stream into wordlike units

Visual Development Supported by rapid maturation of eyes and visual centers in brain Improvements: 2 months: focus 4 months: color vision 6 months: acuity, scanning, and tracking 6–7 months: depth perception © Payless Images/Shutterstock

Milestones in Depth Perception 3–4 weeks Sensitivity to motion cues 2–3 months Sensitivity to binocular depth cues 5–7 months Sensitivity to pictorial depth cues

The Visual Cliff Reveals link between crawling and depth perception Figure 4.11 The visual cliff Figure 4.11

Milestones in Pattern Perception 2 months Becomes sensitive to contrast in complex patterns; prefers them to simple patterns 2–3 months Thoroughly explores a pattern’s features, pausing briefly to look at each part 3–4 months Detects pattern organization, integrating pattern parts into organized whole 12 months Detects familiar objects represented by incomplete drawings

Subjective Boundaries in Visual Patterns Figure 4.12 Subjective boundaries in visual patterns Figure 4.12 (Adapted from Rose, Jankowski, & Senior, 1997.)

Milestones in Face Perception Birth– 1 month Prefers simple facelike pattern to other stimuli 2–4 months Prefers complex facial pattern to other complex stimulus arrangements Prefers mother’s detailed facial features to another woman’s 3 months Distinguishes features of different faces 5–12 months Perceives emotional expressions on faces as meaningful wholes

Early Face Perception Figure 4.13 Early face perception Figure 4.13 (From Cassia, Turati, & Simion, 2004; Johnson, 1999; Mondloch et al., 1999.)

Milestones in Intermodal Perception Birth Perceives amodal sensory properties 3–4 months Matches faces with voices on basis of lip–voice synchrony, emotional expression, and speaker’s age and gender 4–6 months Perceives and remembers unique face–voice pairings of unfamiliar adults

Differentiation Theory Infants actively search for invariant features of the environment notice stable relationships among features of a stimulus, detecting patterns such as individual faces gradually detect finer and finer features