Lifespan Development I: Physical, Cognitive, and Emotional Development in Infancy and Childhood

Developmental Psychology

Introduction to Developmental Psychology

Developmental psychology is the scientific study of how human physical, cognitive, social, and behavioral characteristics change across the lifespan. It examines the processes and factors that influence growth from conception through old age.

• Life periods:

  • Infancy: birth–2 years

  • Childhood: 2–12 years

  • Adolescence: 12–22 years

  • Early Adulthood: 22–45 years

  • Middle & Late Adulthood: 45–60 years & 60+ years

• Early Adulthood: Often involves forming long-term relationships, possibly having children, completing post-secondary education, and launching a career.

Chronological Age and Development

Chronological age refers to the number of years since birth, but it does not directly cause development. Other important dimensions include:

• Biological age: Functioning of body and organs

• Psychological age: Adaptive thinking and coping abilities

• Socioemotional age: Connectedness with others

Research Methods in Developmental Psychology

• Cross-sectional study: Data collected at one point in time from different age groups

• Longitudinal study: Data collected repeatedly over time from the same individuals

• Considerations:

  • Cost and participant attrition

  • Cohort effects: Differences due to being born in different time periods, not necessarily development itself

Infancy: Physical Development

Zygotes to Infants

• Germinal stage (0–2 weeks):

  • Conception: sperm + ovum = zygote

  • Zygote divides, becomes implanted in uterus as blastocyst

  • Blastocyst divides into fetus and placenta

• Embryonic stage (2–8 weeks):

  • Formation of physical structures

• Fetal stage (8 weeks–birth):

  • Development and specialization of skeletal, organ, and nervous systems

Sensory Development

• Babies can respond to and remember auditory stimuli experienced in the womb (e.g., The Cat in the Hat study)

• Preference for mother's voice over others

• Crying with an accent (influenced by prenatal auditory experience)

• Visual acuity is poor at birth but infants are highly responsive to faces and can perceive depth (visual cliff experiment)

• Taste and olfaction (smell) are relatively well developed at birth

Motor Development

• Reflexes: Automatic reactions to stimuli (e.g., rooting, sucking)

• Gross motor skills: Large muscle actions such as crawling and walking

• Fine motor skills: Small muscle actions, such as finger dexterity (e.g., picking up objects)

• Sticky mittens experiment: Early simulated experiences with reaching enhance infants' object exploration skills

Infancy & Childhood: Cognitive & Emotional Development

Piaget’s Cognitive Development Theory

Jean Piaget proposed that cognitive development occurs in stages, each characterized by different abilities and ways of thinking.

• Assimilation: Fitting new information into existing belief systems

• Accommodation: Modifying belief systems based on new experiences

Stages of Cognitive Development

• Sensorimotor stage (0–2 years):

  • Thinking and exploration based on immediate sensory and motor experiences

  • Development of object permanence (understanding that objects continue to exist even when out of sight)

• Preoperational stage (2–7 years):

  • Language development, use of symbols, and pretend play/rs' perspectives

  • Struggles with conservation (understanding that quantity remains the same despite changes in shape or appearance)

• Concrete operational stage (7–11 years):

  • Logical thinking and manipulation of numbers

  • Transitivity problem: Understanding relationships among elements (e.g., if A > B and B > C, then A > C)

  • Seriation: Ability to order objects by a property (e.g., size)

• Formal operational stage (11 years onward):

  • Advanced cognition, including abstract reasoning and hypothetical thinking

  • Ability to solve logical problems and understand complex relationships

Attachment

Attachment refers to the close emotional bond that infants develop with their caregivers, which is crucial for social and emotional development.

• Harlow’s (1958) monkeys: Demonstrated the importance of comfort and security in attachment, not just food provision

• Ainsworth’s (1979) Strange Situation: Identified different attachment styles based on infants' reactions to caregiver separation and reunion

Attachment Style	Description
Secure	Caregiver as secure base; mild distress at separation, happy at return
Insecure avoidant	Little engagement with caregiver, indifferent to return
Insecure anxious/ambivalent	Clingy, distressed by separation, not easily comforted at return
Disorganized	Dazed, confused, fearful, inconsistent behavior

Infants with insecure attachments are more likely to have less effective emotion regulation strategies later in life.

Attachment Styles in Adulthood

• Secure: Positive view of relationships, easily get close to others

• Avoidant: Hesitant about beginning relationships, distance themselves

• Anxious: Demand closeness, less trusting, emotional, jealous, possessive

• Disorganized: Lack of coherent behavior, desire closeness but also fear intimacy

Attachment & Parenting

• Attachment behavioral system vs. caregiving behavioral system: Parenting involves helping children feel loved and secure, not just teaching right from wrong

• Conditioning and discipline:

  • How does it affect children's behavior and self-esteem?

  • Is love and security something that must be earned?

  • Inductive discipline: Explaining the consequences of a child's actions on others to activate empathy

References & Further Reading

• Needham, A., Barrett, T., & Peterman, K. (2002). Sticky mittens and infants' exploratory skills. Infant Behavior & Development, 25(3), 279–295.

• Piaget & conservation, Harlow’s monkeys, and other referenced studies

Additional info: For more on attachment styles, see attachmentproject.com.