Development over the Lifespan
Developmental Psychology : Issues and Methods
Four issues guide developmental research:
1. Nature and nurture: to what extent is our development the product of heredity (nature)
or the product of environment (nurture)?
2. Critical and sensitive periods:
• Critical period: an age range in which certain experiences must occur for
development to proceed normally or along a certain path.
• Sensitive period: is an optimal age range for certain experiences, but if those
experiences occur at another time, normal development will still be possible.
3. Continuity versus discontinuity: is development continuous and gradual, or
discontinuous, progressing through qualitatively distinct stages?
4. Stability versus change: do our characteristics remain consistent as we age?
Developmental functions: portray how different processes change with age
• No change: an ability present at or before birth that remains relatively constant across the
• Continuous change: an ability not present, or very immature, at birth that develops
gradually over months or years and then remains constant over age
• Stages (discontinuity): an ability that progresses in stages, with relatively rapid shifts
from a lower level of performance to a higher level.
• Inverted U-shaped function: an ability that emerges after birth peaks, and disappears
• U-shaped function: an ability that is present early in life, disappears temporarily, and
Cross-sectional design: compare people of different ages at the same point in time (test each
person only once and compare how well the different age groups perform).
• Drawback: cohorts (different age groups) grew up in different historical periods
Longitudinal design: tests the same cohort as it grows older.
Sequential design: combines the cross-sectional and longitudinal approaches.
Three stages of prenatal development of physical growth:
1. Germinal stage
• The first two weeks of development, beginning when one sperm fertilizes a
• Zygote: fertilized egg
• Through repeated cell division the zygote becomes a mass of cells that attaches to
the mother’s uterus about 10 to 14 days after conception
2. Embryotic stage • The end of the second week through the eighth week after conception
• Mass cell is now called an embryo.
• The umbilical cord and placenta develop during this stage
• Placenta: located on the uterine wall, allow nutrients to pass from the mother’s
blood to the umbilical cord.
• The umbilical cord contains blood vessels that carry these nutrients and oxygen to
the embryo, and waste products back from the embryo to the mother.
• Embryotic cells divide rapidly and become specialized.
• Body organs and systems begin to form, and by week 8 the heart of the embryo is
beating, the brain is forming, and facial features (eyes) can be recognized.
3. Fetal stage
• At the 9 week of conception the embryo is called a fetus.
• Lasts until birth
• Muscles become stronger and other bodily systems continue to develop
• 24 weeks: the eyes open
• 28 weeks: attains the age of viability (it is likely to survive outside the womb in
case of premature birth)
Genetics and Sex Determination
• At conception, an egg and a sperm unite to form a zygote (23 pairs of chromosomes)
• The 23 pair of chromosomes determines the baby’s sex.
• A genetic female’s 23 pair contains two X chromosomes, and the 23 chromosome in
the egg is always anrd. rd
• A genetic male’s 23 pair contains an X and Y chromosome (XY). The 23 chromosome
contains a specific gene, known as the TDF (testis determining factor) gene, that
triggers male sexual development.
• 6-8 weeks after conception the TDF gene initiates the development of testes. Once
formed, the testes secrete sex hormones called androgens that continue to direct a male
pattern of organ development.
• Teratogens: environmental agents that cause abnormal prenatal development. The
placenta prevents many dangerous substances from reaching the embryo and fetus, but
some harmful chemical molecules and diseases can pass through.
o If the mother contracts rubella, it can cause blindness, deafness, heart defects, and
mental retardation in the infant.
o STD’s can produce brain damage, blindness, and deafness.
o Fetal alcohol syndrome (FAS): a group of severe abnormalities that results from
prenatal exposure to alcohol. FAS children have face abnormalities and small,
malformed brains. Psychological symptoms of FAS may include intellectual and
fine- and gross-motor impairments and poor adaptive functioning.
o Nicotine increases the risk of miscarriage, premature birth, and low birth weight.
o Babies of pregnant mothers who use cocaine and heroin are often born addicted
and experience withdrawal symptoms after birth. • Relatively loud sounds elicited reliable increases in fetal heart rate and body movements
during the third trimester of pregnancy.
• Fetuses learn to stop responding to repeated presentations of vibroacoustic and auditory
stimuli, reflecting short-term memory.
• Fetuses have a long-term memory for sounds they hear repeatedly during fetal
• Newborns prefer sounds that become familiar to them during their last months of fetal
development (e.g. mother’s voice).
• Fetuses learn about odours from their pregnant mother’s diet. The newborns of mothers
who habitually consumed anise-flavoured foods and drinks also preferred anise odours.
Infancy and Childhood
The Amazing Newborn
Newborn Sensation and Perception
• Preferential looking procedure: to study infants’ visual preferences.
o Placed infants on their backs, showed them two or more stimuli at the same time, and
filmed their eyes to record how long they looked at each stimulus.
o Infants preferred complex patterns, such as realistic or scrambled drawings of a
human face, to simple patterns and solid colours.
• Infants have poor visual acuity
o Newborn’s resolution threshold at about 20/800, or 40 times worse than normal
adult acuity of 20/20.
• Visual habituation procedure: used to establish a new visual preference. The same
stimulus is presented repeatedly until infant looking time declines.
o Infants usually look longer at a novel rather than familiar stimulus.
• Auditory habituation procedure: to study infant memory. Recorded 2-day-olds’ head-
turning toward an off-centered, recorded speech sound. After about 16 presentations,
infants stopped turning to face the now familiar sound.
o Newborns rapidly learn to associate particular sounds with particular objects (e.g.
mother’s face and voice)
• Newborns can learn through classical and operant conditioning and imitation.
• Newborn’s visual field in each eye expands almost to adult size by 6 months of age.
• 3-4 months, infant pattern perception is organized according to certain Gestalt principles
(closure and proximity), while other Gestalt principles appear later in a steplike fashion
• U-shaped function exists for sound localization-the remarkable ability of newborns to
turn toward sounds at birth disappears in the 2 month of life and returns again at 4-5
months of age.
• Auditory patterns perception is also relatively advanced in young infants, who can detect
tiny changes in adult speech sounds that differentiate one word from another by 1-2
months of age.
• Good at detecting changes in phonemes not found in their parents’ language • Good at detecting changed in phonemes not found in their parents’ language. They lose
this ability by 12 months, as they began to speak words in their native language.
• Infants appear to perceive extensive music as adults do.
• 2 months of age, infants remember a short melody after listening to it repeated 15
Physical, Brain, and Motor Development
• Maturation: the genetically programmed biological process that governs our growth.
• Cephalocaudal principle: reflects the tendency for development to proceed in a head-to-
o The head of a fetus is disproportionately large because physical growth
concentrates first one the head.
• Proximodistal principle: states that development begins along the innermost parts of the
body and continues toward the outermost parts. The fetus’s arms develop before the
hands and fingers and at birth infants can control their shoulders, but not their arm or
The Young Brain
• At birth, the newborn’s brain is far more mature and has reached only about 25% of its
eventual adult weight. By 6 months, the brain reaches 50% of its adult weight.
• Motor skills develop rapidly
• The last areas to mature is the frontal cortex.
• Follow a stagelike sequence
• Reflexes: automatic “inborn” behaviours elicited by specific stimuli (e.g. breathing)
Environmental and Cultural Influences
• Malnutrition stunts general growth and brain development and is a major source of infant
• Depriving well-nourished rat pups of normal physical contact with their mothers stunts
• Massaging human infants accelerates their weight gain and neurological development
• Infants, when raised in cultures in which parents restrict walking experiences, walk later.
• Infants, when raised in cultures in which parents exercise their walking, walk sooner.
• Experience plays a critical role in the development of sensory, perceptual, motor, and
• Three points that apply across the realm of human development:
o Biology sets limits on environmental influences (the best nutrition will not enable
most people to grow 2.5 metres taller)
o Environmental influences can be powerful (Nurturing environments foster
physical, sensory-motor, and psychological growth).
o Biological and environmental factors interact (Enriched environments enhance
brain development. In turn, brain development facilitates our ability to learn and
benefit from environmental experiences) Cognitive Development
Piaget’s Stage Model
• Proposed that children’s thinking changes qualitatively with age, and that it differs from
the way adults think.
• Believed that cognitive development results from an interplay of maturation and
• Cognitive development occurs as we acquire new schemas, and as our existing schemas
become more complex. Two key processes are involved:
1. Assimilation: is the process by which new experiences are incorporated into existing
2. Accomodation: is the process by which new experience cause existing schemas to
4 major stages of cognitive growth
1. Sensorimotor stage: from birth to age 2, infants understand their world primarily
through sensory experiences and physical (motor) interactions with objects.
• 8 months: object permanence (the understanding that an object continues to exist
even when it no longer can be seen.
• Infants begin to acquire language after age 1
• 2 years: plan, form simple concepts, solve some problems mentally, and
communicate their thoughts to others.
2. Preoperational stage: At around age 2, they represent the world symbolically through
words and mental images but do not yet understand basic mental operations or rules.
• The preoperational child does not understand conservation (the principles that
basic properties of objects, such as their volume, mass, or quantity stay the same
even though their outward appearance may change)
• Thinking at this age displays irreversibility: it is difficult for them to reserve an
• Preoperational children exhibit centration; they focus on only one aspect of the
• Preoperational children’s thinking also reflects egocentrism (difficulty in viewing
the world from someone else’s perspective. Belief that other people perceive
things in the same way they do).
3. Concrete operational stage: 7 and 12 years old, could perform basic mental operations
concerning problems that involve tangible (concrete) situations.
• Grasp the concept of serial ordering (easily arranging a set of objects along
• Formed mental representations of a series of actions (drawing a map showing the
route to get to school)
• Difficulty with hypothetical problems or problems requiring abstract reasoning
(rigid types of thinking).
4. Formal operational stage: begins around 11-12 years of age, individuals think logically
about both concrete and abstract problems, form hypotheses, and systematically test them
• Begin to think more flexibly. Assessment of Piaget’s Theory
Piaget’s universality principle
• Proposed a universal theory for cognitive development
• The general cognitive abilities associated with Piaget’s four stages occur in the
same order across cultures.
Early understanding of the physical world
• Children acquire knowledge earlier than Piaget proposed.
• Violation-of-expectation-experiment: test an infant’s understanding of basic concepts by
seeing what they pay their attention to (pay more attention to events that violate their
understanding of the world).
o 4 months: basic understanding that solid objects can’t be in the same place at the
same time (rudimentary sense of object permanence)
o 5 months: ability to add and subtract small numbers of objects.
Vygotsky: The Social Context of Cognitive Development
• Highlighted how sociocultural context interacts with the brain’s biological maturations.
• Zone of proximal development: the difference between what a child can do
independently and what a child can do with assistance from adults or more advanced
• Continuous, gradual process in which the same set of information-processing abilities
becomes more efficient over time.
• Older children are better able to search systematically for relevant information.
Processing speed, attention, and response inhibition
• The speed in which children process information becomes faster with age.
• Children’s attention span and ability to inhibit impulsive responses to distracting stimuli
also improve with age.
• Younger children have a problem with cognitive flexibility and selective attention.
Working memory and long-term memory
• Working memory improves with age.
• Older children can retain and manipulate visuospatial information in working memory
more effectively than younger children.
Theory of Mind: Children’s Understanding of Mental States
Theory of mind: refers to a person’s beliefs about the mind and the ability to understand other
people’s mental states.
• Piaget believed that children younger than 6 or 7 had difficulty recognizing what people
Lying and deception
• People with a false belief understanding are more likely to lie, starting as early as 3 years
Perspective taking and e