wise, fast learner
聰 centers on sharp mental perception: being wise and quick to understand, like a fast learner who grasps things clearly.
聰 combines 耳 (ear) with 悤, which likely contributes both sound and the idea of quick understanding. The right side 悤 contains 心 (heart/mind), reinforcing the mental aspect. The exact historical development of 悤 is uncertain.
An ear 耳 beside a shape that includes a heart 心: imagine listening with your whole mind, absorbing knowledge quickly and becoming wise.
For ソウ, picture a wise soul (ソウ) whose fast learning comes from deep listening: soul -> ソウ, and the ear 耳 catches every word.