Final answer:
In nonindustrialized countries, the concept of middle age is often undefined, with adults referred to as young or old, unlike in the United States where detailed age categorizations like middle adulthood exist.
Step-by-step explanation:
Cross-cultural studies show that in nonindustrialized countries, the concept of middle age may not be as precisely defined as it is in industrialized countries. In such cultures, adults are often referred to simply as young or old, indicating a lesser degree of differentiation within the adult life stages. Industrialized nations like the United States, on the other hand, offer more detailed age categorizations within adulthood, such as middle adulthood which begins in the mid-30s and continues until the mid-60s. During this stage, individuals often achieve career goals, raise families, and begin to experience signs of physical aging and increased health risks. Conversely, nonindustrial societies may not have established terms or social constructs for stages like the young-old, middle-old, and old-old. Sociological factors such as life expectancy, access to healthcare, and economic development influence these cultural perceptions and distinctions of aging.