Psychologists today recognize childhood as a separate stage of life which can only be understood in its own terms, and they wonder why the Western world took so long to see the folly of regarding children simply as small, inadequately socialized adults. Most psychologists, however, persist in regarding people 70 to 90 therefore, to acknowledge that serious research into the unique psychology of advanced age has become indispensable.
What this question is testing
Conclusion
The author wants psychologists to take old age seriously as a distinct stage and study it accordingly.
Evidence
Two key facts. First: psychology already accepts childhood as a separate stage. Second: society's economic organization treats old age as fundamentally different too.
Evaluate
To strengthen this with a principle, we need a rule that connects the economic-organization fact to the call for distinct research. Something like: when society treats two age groups as fundamentally different in how its economic life is organized, those groups have their own distinct psychologies and should be studied accordingly.
Goal
Find the principle that bridges economic-organization → distinct psychology.
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