Final answer:
Developmental psychologists identify two types of cognitive abilities: fluid intelligence and crystallized intelligence. Fluid intelligence may decline in late adulthood, while crystallized intelligence typically remains stable or improves over time.
Step-by-step explanation:
Developmental psychologists have studied cognitive abilities and have delineated between two types: fluid intelligence and crystallized intelligence. Fluid intelligence, the ability to see complex relationships and solve problems, tends to decline in late adulthood. This decline can be mitigated to some extent by engaging in mentally and physically stimulating activities which can reduce the incidence of cognitive decline. In contrast, crystallized intelligence, characterized by acquired knowledge and the ability to retrieve it, remains relatively steady or may even improve with age. Adults often show stable or increasing scores on intelligence tests until their mid-30s to mid-50s.
The relationship between aging and these forms of intelligence aligns with the broader spectrum of cognitive development theories, ranging from the work of Cattell to more contemporary cognitive developmental researchers.