Psych 315: Childhood and Adolescence

Biology and Behavior

Physical, Perceptual, and Motor Development

Announcements: Teaching Assistants:• Jeremy Frimer (Section 002)• Office: Kenny Bldg. Room 1101 (corner of West Mall and University)• Office hours: Tuesdays 3:30-4:30pm or by appointment• E-mail: jeremyfrimer@gmail.com

• Kathryn Dewar (Section 001)• Office: Kenny Bldg. Room 1101 (corner of West Mall and University)• Office hours: TBA or by appointment• E-mail: kathrynd@psych.ubc.ca

• Text ( on reserve), • additional readings will be assigned the week

before.

Genetic and Environmental Forces

Model Components:• Genotype: The genetic material we inherit from our parents.• Phenotype: The observable expression of the genotype, including bodily characteristics and behavior.• Environment: Every aspect of an individual’s surroundings other than the genes themselves.

Development

Development is a joint function of genetic and environmental factors. The four numbered relations are discussed in detail in the text.

Parents’ Genotype Child’s Genotype Every cell has 46 chromosomes (23 pairs), except germ

cells (23 chromosomes) ½ of genetic inheritance comes from mom and the other ½

from dad Sex Determination by Sex Chromosomes

Females XX Males XY—presence of the Y chromosome determines male sex

Diversity1. Mutations—random spontaneous errors2. Random assortment of chromosomes in egg and sperm (over 8

million possible combinations)3. Crossing over—chromosomes swap some DNA sections

Child’s Genotype = ~100% Nature (+ mutations which can sometimes be the result of environment)

Child’s Genotype Child’s Phenotype• A child will not express every characteristic in its genetic makeup.

• E.g. some traits, such as straight hair, require matching “recessive” alleles, others, such as curly hair, require only one “dominant” allele which overrides recessive from other parent.

Mendelian inheritancepatterns

GenotypePhenotype

• Few patterns are as simple as Mendelian inheritance• Regulator genes control the activity of other genes.• Most traits and behaviors of interest to behavioral

scientists (e.g. shyness, aggression, risk-taking behavior, and empathy) involve contributions by several genes = polygenic.

Child’s Environment Child’s Phenotype

•Depending on the environment–genotype relationship, numerous phenotypes may result

•Genotypes are expressed differently in varying environments. The norm of reaction is the range of all possible phenotypes in relation to all possible environments. (e.g. revisit oak tree analogy)

e.g. intelligence

• Parents’ role—highly literate parents may have more books in the home, exposing children to more literature

Child’s Phenotype Child’s Environment

1. They actively select surroundings and experiences conducive to their interests, talents, and personality characteristics (increasing influence with age).

2. They evoke certain responses from others

(e.g. temperament, appearance).

Phenotype Environment E.g. Appearance

• Humans (adults and children alike) behave differently toward more attractive individuals– E.g. halo effect

• Even newborns prefer to look at attractive faces

• Attractive mask study = more pleasure, more active and involved in play, less withdrawal than less attractive mask.

+ =

*What makes a face attractive?To us, and to a baby

• Symmetry?• Smooth/blemish-free complexion?• Darker skin?• Baby-facedness?• Contrast?• Average-ness?Why might infants be predisposed to attend to (prefer)

attractive faces? How might such a preference influence their development?

N&N Interactions• The influence is bi-directional.

• Transactional Model = continuous interaction between N&N– e.g. Temperament = risk or protective factor (starts a

chain of events)

• Direct vs. Indirect Effects – Direct: (e.g. fearful/inhibited leads to social withdrawal)

– Indirect: (e.g. fearful/inhibited leads to social withdrawal which leads to poor social understanding)

• Most people get a “double whammy” (share both their genes and their environment with parents) – (e.g. parents that like to read)

Behavioral Genetics• area of psychology concerned with how variation in behavior

and development results from the combo of genetic and environmental factors.

• Heritability = an estimate of the proportion of measurable difference/variability on a given trait (e.g. intelligence), in a given population (living in a particular environment at a particular period of time), is due to genetic differences

• All behavioral traits are heritable to some extent– Substantial heritability: infant activity level, antisocial behavior,

reading disabilities, divorce, tv viewing• Note: genes do not code specifically for behavior patterns but they can affect

underlying processes that predispose us to attend to certain things more, find some things more interesting/stimulating than others etc. (e.g. novelty seeking/easily habituated increase chances of divorce)

Behavioral Genetics

• 3 types of designs:– 1. Twin Studies

– 2. Adoption Studies

– 3. Twin Adoption Studies (Rare)

Environmental Effects

• Shared Genetic Effects: Heritability estimates rarely exceed 50%, indicating the large contribution of environmental factors.

• Shared Environmental Effects: can be tested among adoptive siblings/biologically unrelated people who grew up together.

• Nonshared Environmental Effects: (those unique to the individual) can be measured by identical twins who grew up together.

Brain Imaging

•Positron Emission Tomography (PET scan)Radioactive sugar is traced

Functional Magnetic Resonance Imaging (fMRI)iron in blood is tracedNot typically done until the child is 6 years old

Brain Imaging

Electrophysiological Recording (EEG) or Event-related Potentials (ERPs)

electrical impulses/activity, Popular method to use on children

ERPs (Video clip!)

The Neuron

The human cerebral cortex

Oversimplification:

Occipital ~ Vision

Temporal ~ Auditory, Emotions, Visual recognition, memory?

Parietal ~ Spatial processing, sensory integration from PSC

Frontal ~ “executive” tasks (e.g. planning, organizing, working memory, inhibition),

--last to fully develop Frontal Lobe Dev./Inhibition Video

The human cerebral cortex

• Contralateral processing• Left ~ Linear/sequential• Right ~ Holistic/global Severed Corpus Collosum (lateralization) Video!

Developmental Processes

Neurogenesis—proliferation of neurons through cell divisionOccurs from the 3rd/4th week to the 18th week

Myelination—insulation around the axonOccurs prenatally through late adolescence

Synaptogenesis—each neuron forms 1000s of connectionsOccurs prenatally, with rapid development right before

and after birth

Synapse Elimination— “pruning” of excess synapsesOccurs prenatally through adolescence

The Brain and Experience• Plasticity: The capacity of the brain to be

affected by experience.• Critical/sensitive periods (time window where

input can organize the brain, when the sensitive period ends, neural organization is typically irreversible)

– E.g. near vs. far–sightedness– E.g. Strabismus—“lazy eye”– E.g. Signers (auditory cortex is put to a better purpose)– E.g. cellists/violinists (extra cortical representation of fingers)– E.g. Ability to hear all phonemes of the world’s

languages

Pruning and Conditioned Head Turn Procedure (Werker video)

Brain Plasticity and Braille Study Video

Brain Damage and Recovery

• “worst time” to suffer brain damage = very early stages of prenatal development and first year after birth (neurogenesis is occurring).

• “best time” = early childhood when synapse generation and pruning are occurring (Plasticity is highest)

Brain Damage and Recovery

Perceptual, Physical, and Motor Development:

The Basics

The Body—Physical Growth and Development

• humans undergo a long period of growth and development.

• Growth spurts are steep in first two years of life and in early adolescence.

• Adolescent girls experience growth burst earlier than boys.

• Body composition (the proportion of fat and of muscle) changes with age (gender dependent).

• Failure to thrive (FTT): infants become malnourished and fail to grow or gain weight for no obvious medical reason; associated with disturbances in mother–child interactions/emotional bond (e.g. orphans).

Importance of Proper Nutrition• 40% of world’s young children

under/malnurished (result of poverty or poor education)

• Proper Nutrition is vital to proper physical and cognitive development – direct (e.g. illness, brain damage)– Indirect (e.g. low energy lack of exploration of

environment, underdeveloped appearance treated as ‘younger’ by peers/adults)

• Breast-feeding provides antibodies against infectious agents

Prenatal PerceptionSensory structures are present relatively early in prenatal

developmentHearing - last trimester fetus’ heart rate responds to external

noises (e.g. voices)Taste - preference for sweet flavors (e.g. DeSnoo treatment for

women with excess amniotic fluid)- at 5 months preferred carrot juice if Mom drank carrot

juice frequently near end of pregnancyTouch - some tactile stimulation in womb Smell - can likely smell coffee, curry etc in amniotic fluid, at

birth prefer the familiar scent of Mom’s amniotic fluidVision - limited visibility, but will orient to external light

Visual Perception• Infants prefer high contrast (e.g Black and white checkerboard)

• poor color vision for the first 3 months

• ~8 months = adult’s vision

• Role of environment (e.g. Genie, college students)

Depth Perception: The Visual Cliff

Depth Perception and Fear

• 1 month olds lowered over the cliff have decelerated heart rates over the deep side indicating they perceive the difference but are interested -- not afraid!

• New crawlers will cross the deep side of the cliff• Experienced crawlers won’t cross the “visual

cliff”• Role of active experience with depth.

Sound, Smell, and Touch

SoundAuditory localization = the ability to identify the location of

a sound source (e.g 10 mins after birth)

Children are slightly “deaf” compared to adults until age 5-8Smell• 2 week-old infants prefer own mother’s breast milk scent to

another mother’s.Touch• Oral exploration dominates in the first 4 months

Putting it all together: Intermodal Perception

• Intermodal perception = combining info from two or more sensory systems (modalities)

• Important skill for integrating sensory info (e.g. looking at a soft thing and knowing how it will feel, or feeling something and knowing how it will look)

• 29-day old infants were given either a round pacifier or a nubby pacifier and did not see it. Later, when they were shown both pacifiers they looked longer at the one they had sucked on

Intermodal Perception

Intermodal Counting

Perception & Motor Development

• At each new locomotor “stage” they have to learn to integrate their perceptual info with their new motor skills

• (e.g. “gap” experiments)

Aspects Involved in Motor Development• Brain maturation and body proportion

changes (Nature)• Physical strength, posture, and balance

(both Nature and Nuture)• Perceptual skills (both N&N)• Motivation (both N&N)• Cultural and Environmental Factors (back vs

belly sleepers, e.g. Malian babies) (Nurture)

Malian Baby Exercises Facilitate Motor Development

“To Walk” Video