How many primary mental abilities did Louis Thurstone identify?

Louis Thurstone identified 7 primary mental abilities, rejecting the idea of a single general intelligence (g) that was dominant in other theories of intelligence at the time. Instead, he proposed that intelligence consists of multiple distinct factors. These primary mental abilities include verbal comprehension, numerical ability, spatial relations, perceptual speed, word fluency, memory, and reasoning. Thurstone's work laid the groundwork for a more nuanced understanding of intelligence, emphasizing that people may excel in certain mental abilities while performing average or poorly in others. This multifactor approach provides a framework for assessing cognitive strengths and weaknesses in educational and psychological evaluations.