AP® Psychology · Unit 3 · Topic 3.1
Stability, Change, and Continuous Development
Developmental psychologists debate whether growth happens in distinct, qualitatively different stages or as one smooth, continuous ramp of gradual change, and separately ask whether early traits stay stable or shift over a lifetime.
Picture a skill, like logical reasoning, measured from age 2 to age 16. A stage model predicts a staircase: long flat stretches where ability barely changes, then a sudden jump when a child reorganizes how they think, then another plateau. A continuous model predicts a ramp: a steady upward slope with no sudden jumps, just more of the same kind of thinking, done better and faster with practice and brain maturation. Same skill, same age range, two different predicted graphs, that is the actual disagreement.
The stage view says development is qualitative. At each stage the person thinks in a fundamentally different way, not just a better version of the old way. The continuous view says development is quantitative. Skills accumulate gradually, and what looks like a jump is really just the smoothing-over of many small steps measured too coarsely. Neither side denies that people change. They disagree about the shape of the change.
A second, related theme runs across a whole life rather than one skill: stability versus change. Take one person and ask whether their traits at 15 predict their traits at 75. Stability would mean a shy teenager stays a reserved elder. Change would mean life events, relationships, and new roles substantially reshape personality, so early traits predict little decades later. This theme connects to stages and continuity because both questions ask the same underlying thing: does the early blueprint fix the outcome, or does the organism keep rewriting itself. The next topics in the unit, on conditioning, show one mechanism for that rewriting.
Key terms
- Stage model
- A view of development as a sequence of qualitatively distinct periods, each with its own characteristic way of thinking or behaving.
- Continuous model
- A view of development as a gradual, steady accumulation of skills and knowledge without sudden qualitative shifts.
- Qualitatively distinct
- Different in kind, not just in amount or degree, such as a new way of reasoning rather than a faster version of the old way.
- Stability versus change
- The developmental theme asking whether a person's traits established early in life stay consistent or shift substantially across the lifespan.
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End of topic.