Final answer:
Intelligence is best defined as the ability to think and reason clearly, and to act purposefully and effectively when adapting to the environment. This definition encompasses both fluid and crystallized intelligence, capturing the multifaceted nature of cognitive abilities.
Step-by-step explanation:
The best definition that describes intelligence, among the options given, is 'c. The ability to think and reason clearly and to act purposefully and effectively in adapting to the environment'. This inclusive definition captures the essence of both fluid and crystallized intelligence, elements fundamental to understanding what intelligence entails. Fluid intelligence is the capacity to see complex relationships and solve novel problems, and is crucial for adapting to new situations and thinking abstractly. On the other hand, crystallized intelligence involves the use of acquired knowledge and the ability to retrieve and apply this knowledge effectively, a critical aspect in tackling concrete factual problems.
Additional concepts related to intelligence include creative intelligence, which highlights the ability to produce novel solutions or ideas, and analytical intelligence, characterized by the ability to analyze and evaluate problems, often used in academic settings. A comprehensive understanding of intelligence also considers cognitive psychologists' perspectives, theories like the Cattell-Horn-Carroll theory, and the integration of diverse cognitive abilities within hierarchical models.
It is noteworthy that problem-solving strategies and obstacles such as mental set and confirmation bias are also part of the intelligence discourse, considering their impact on effective decision-making and creative thought.