5 Infancy

What does developmental psychology study?

Human psychological changes across the lifespan (physical, cognitive, social, moral).

What is the nature vs. nurture debate?

Whether development is driven more by biological maturation or experience and learning

What is the difference between continuous and stage-based development?

Continuous development is gradual; stage-based development occurs in distinct steps.

What is a cross-sectional study?

Research comparing different age groups at a single point in time.

What is a longitudinal study?

Research tracking the same individuals across multiple time points.

What are the Ecological Systems Model

development influenced by multiple environmental systems (CONTEXT)

Transactional Model

nature and nurture constantly influence and change each other

• t is in both 

What is equifinality?

Different causes can lead to the same outcome.

What is multifinality?

The same cause can lead to different outcomes.

When does prenatal development begin and end?

Begins at conception and ends at birth.

What are teratogens?

Environmental agents (e.g., alcohol, lead, mercury, insecticides) that cause physical or neurological abnormalities.

During which period are teratogens most dangerous?

When the developing tissue (especially brain) is undergoing rapid formation.

What major events occur in Weeks 1–4 of pregnancy?

Ovulation, fertilization, mitosis, implantation.

What forms during Weeks 5–6?

Neural tube (future brain and spinal cord), eyes begin forming, heart may start beating.

What major brain development occurs during Weeks 7–8?

Brain divides into hemispheres; 100 nerve cells created per minute.

When is the embryo considered a fetus?

Week 9

What develops in Weeks 10–11?

Dendrites and synapses; head is half of the body.

By Week 12, what is true about the brain?

All major structures have formed; it will continue to grow.

What happens in Weeks 13–21 (2nd trimester)?

Baby reacts to noise, develops sleep cycles, sex can be detected.

What is the youngest week of gestation with recorded survival?

Week 21.

apoptosis

Programmed cell death

when does apoptosis occur?

begins around Week 23 (40–60%)

When is a fetus considered viable?

Around Week 24.

What major developments occur Weeks 25–28?

Rapid axon/dendrite growth; baby senses sound, light, and flavors; weighs >2 lbs.

What happens in the third trimester (Weeks 29–40)?

Myelination begins; temperature regulation improves; lungs mature; baby doubles in size.

When is a baby considered full-term?

37 weeks.

What behaviors are reflexive at birth?

Rooting, sucking, blinking, Babinski, palmar grasp, Moro reflex.

When is synaptic production at its peak?

During the first year of life.

What is synaptic pruning and when does it occur?

Elimination of unused connections; begins in infancy and continues to ages 4–6.

What voice can infants recognize at birth?

Their mother's voice.

What language ability do newborns have related to prosody?

Can distinguish native vs. non-native languages if rhythms differ

What type of stimuli do infants prefer?

Social stimuli.

What is the High-Amplitude Sucking Paradigm?

Method where babies suck harder in response to new or changed stimuli.

What is the Preferential Looking Paradigm?

Babies look longer at interesting or surprising stimuli; used to measure preference and recognition.

When do non-reflexive motor movements appear?

Around 1 month old.

When do planned motor movements begin?

Around 4 months.

cephalocaudal

proximodistal rules

development from the center outward.

When do crawling and walking typically emerge?

Between 6–9 months.

What is infant amnesia?

Inability to form lasting memories before ~8 months.

How long can infants retain memories at 8 months?

About 24 hours

How long can 2-year-olds retain memories?

Up to one year.