Much of classical developmental psychology, particularly early in the field's history, focused heavily on childhood and adolescence, implicitly treating adulthood as a relatively fixed, already-completed endpoint rather than a period of continued genuine psychological development. Erik Erikson's stage theory pushed back against that framing directly, proposing that psychological development continues across the entire human lifespan, all the way through old age, with each distinct life stage organised around its own specific psychosocial challenge or question that a person works through during that particular period of their life.
Eight stages, each built around a specific tension to resolve
Erikson's theory describes eight sequential life stages, each characterised by a specific central tension between two opposing outcomes — trust versus mistrust in infancy, for instance, or identity versus role confusion during adolescence — with how a person navigates that stage's particular tension shaping their psychological development going forward into later stages. Crucially, Erikson didn't stop this framework at adolescence or early adulthood the way many earlier developmental theories effectively had; his later stages address challenges specific to middle and older adulthood, including generativity versus stagnation, broadly concerning whether a person feels they're contributing meaningfully to future generations, and integrity versus despair, concerning how a person makes sense of and evaluates their life as a whole as they approach its natural end.
Later stages depend on how earlier ones were navigated, but aren't fixed by them
A key feature of Erikson's model is that the stages build on each other sequentially: how a person navigates an earlier stage's central tension can influence how well-equipped they are to navigate later ones, without that influence being simply deterministic or irreversible — someone who struggled significantly with an earlier stage's central challenge isn't thereby permanently locked out of successfully navigating a later one, since Erikson's framework treats each stage as offering its own fresh, largely independent opportunity to develop the psychological strength that stage is specifically organised around, rather than treating a person's entire subsequent development as rigidly fixed by how any one earlier stage happened to resolve.
What we're still unsure about
Erikson's eight-stage framework and its historical significance in shifting developmental psychology's attention beyond childhood and adolescence toward the full lifespan are well documented in the history of psychology. What's more genuinely debated among developmental psychologists today is how precisely age-bound and universally sequential Erikson's specific stages actually are in practice, given how much individual life circumstances, culture and historical period can shape when, and even whether, a person confronts a given stage's central psychosocial question in the particular form and timing Erikson originally described — later researchers have proposed various modifications and extensions to the original model, and there's no single fully settled consensus on exactly how rigidly age-linked the theory's stages should be treated as being.
This sits inside Lifespan Development & Ageing, one of seven topics in Developmental Psychology, one of four domains in Psychology, one of seventeen subjects the app can quiz you on.