Formal:
* Astuteness: This word emphasizes a keen and shrewd understanding of people and situations.
* Discernment: This word focuses on the ability to make fine distinctions and judgments.
* Sagacity: This word implies wisdom and good judgment, often gained through experience.
* Perceptiveness: This word emphasizes the ability to notice and understand subtle cues and details.
Informal:
* Sharp: This word implies a quick and alert mind.
* Clever: This word suggests an ability to think creatively and solve problems.
* Insightful: This word emphasizes the ability to see beyond the surface and understand the deeper meaning of things.
The best word to use will depend on the specific context and what you want to emphasize.