Final answer:
Raymond Cattell and John Horn concluded that fluid and crystallized intelligence are the most crucial aspects of intelligence. Crystallized intelligence is acquired knowledge and the ability to retrieve it, while fluid intelligence involves solving complex problems and recognizing patterns.
Step-by-step explanation:
The two researchers who concluded that fluid and crystallized intelligence are the most crucial aspects of intelligence were Raymond Cattell and John Horn (b). In Cattell's theory of intelligence, he divided general intelligence into two components: crystallized intelligence and fluid intelligence. Crystallized intelligence refers to acquired knowledge and the ability to retrieve it, while fluid intelligence encompasses the ability to see complex relationships and solve problems.