Human Development and Psychological Growth Principles
Habituation and Dishabituation
Habituation refers to getting used to something. When you show the same stimulus repeatedly, looking time decreases with each presentation. This means the infant recognizes or remembers the stimulus, essentially thinking, “I’ve seen this already.”
Dishabituation is the act of noticing something has changed. First, you habituate the infant to a stimulus, then you show a new or different stimulus. If looking time increases again, the infant has detected the difference. Dishabituation always requires habituation first.
Senescence and Cellular Aging
Senescence is the normal deterioration of cells as we age. Telomeres are protective pieces of DNA at the ends of chromosomes. Every time a cell divides, its telomeres become shorter. Eventually, they become too short for the cell to safely divide, so the cell enters senescence and stops dividing. Telomerase is an enzyme that can rebuild and maintain telomeres.
LTP and LTD: Synaptic Plasticity
LTP (long-term potentiation) happens when a synapse is activated frequently, causing the connection between neurons to become stronger. This can promote synaptic growth and is important for learning and memory. LTD (long-term depression) is the opposite: lower-frequency activity causes the connection to become weaker, which can contribute to pruning unnecessary synapses. In simple terms, LTP strengthens useful connections, while LTD weakens less-used connections.
The Eight Lifespan Stages
The eight lifespan stages describe the major periods of human development:
- Prenatal
- Infancy/Toddlerhood (0–2)
- Early Childhood (3–6)
- Middle Childhood (7–11)
- Adolescence (12–18)
- Emerging Adulthood (19–25)
- Adulthood (26–65)
- Late Adulthood (66+)
Basically, development continues throughout your entire life, not just during childhood.
Cognitive Development and Piaget’s Theory
Piaget may have underestimated how capable children actually are. A child might say the wrong answer but gesture the correct answer; this is called a gesture-speech mismatch. This suggests the child understands more than their verbal answer shows, meaning cognitive development may not fit into Piaget’s strict stages as neatly as he proposed.
Suggestibility and the Misinformation Effect
Suggestibility: Children who can give more detailed and accurate verbal descriptions of an event are less suggestible, meaning they are less likely to have their memory changed by misleading information afterward. This connects to the misinformation effect, where information learned after an event can alter a person’s memory of the original event.
Kohlberg’s Stages of Moral Development
Pre-conventional Morality
Pre-conventional morality is based on yourself and consequences. In Stage 1, you behave to avoid punishment: “I won’t steal because I’ll get punished.” In Stage 2, you act out of self-interest or reward: “I’ll help you because I’ll get something in return.”
Conventional Morality
Conventional morality is based on society and its rules. In Stage 3, you behave according to social norms and approval: “I won’t steal because people will think I’m a bad person.” In Stage 4, you focus on law and order: “I won’t steal because stealing is against the law and laws keep society functioning.”
Post-conventional Morality
Post-conventional morality means you think beyond simply following laws. In Stage 5, you see laws as a social contract designed to benefit society, but you recognize that unfair laws can be changed. In Stage 6, decisions are based on universal ethical principles such as justice, equality, and human rights, even when those principles conflict with laws.
Expertise, Wisdom, and Adolescent Risk-Taking
Expertise: Deep, organized knowledge in a specific domain. Wisdom: Knowledge and intelligence guided by ethics and the common good. Adolescent risk-taking: The limbic reward and emotion system matures before the frontal lobe, which is responsible for judgment and impulse control.
Walker’s Cycle of Violence
Walker’s Cycle: Tension building → Explosion/abuse → Honeymoon/reconciliation → Repeat. A healthy outcome requires breaking or leaving the cycle.