そうですか。それは知りませんでした。 — Is that so? I did not know that. (Cultural · Communication, Universal, JLPT N4)

Gesture & etiquette

A slight raise of the eyebrows and forward lean with rising intonation expresses genuine surprise. A simple nod with falling intonation signals calm acknowledgment. The combined phrase adds genuineness — admitting you did not know something shows openness and humility.

So desu ka' is one of the most versatile Japanese responses — it can express surprise, confirmation, understanding, or polite acknowledgment depending on tone and pitch. A rising intonation signals genuine surprise; a falling intonation signals calm acknowledgment. Overusing it can seem dismissive — vary with 'naru hodo' or 'honto desu ka?'