かと思うと details
write + (past) + just when it looked like X — and straight away something else, usually the reverse
kaita katoomouto
just when it looked like X — and straight away something else, usually the reverse
泣いているかと思うと、もうけらけら笑っている。
naite iru ka to omou to, mou kerakera waratte iru.
One minute he's crying, and the next he's cackling away. neutral
帰ってきたかと思ったら、もう出ていったよ。
kaette kita ka to omottara, mou dete itta yo.
He'd barely got home before he was out the door again. casual
- colloquial
Examples
just when it looked like X — something else follows on the same breath, usually its reverse, and the speaker is watching it happen
泣いているかと思うと、もうけらけら笑っている。
naite iru ka to omou to, mou kerakera waratte iru.
One minute he's crying, and the next he's cackling away. neutral
帰ってきたかと思ったら、もう出ていったよ。
kaette kita ka to omottara, mou dete itta yo.
He'd barely got home before he was out the door again. casual
社長はお戻りになったかと思うと、すぐにまたお出かけになりました。
shachou wa o modori ni natta ka to omou to, sugu ni mata o dekake ni narimashita.
The president had barely returned before he went out again. formal
Formation
{V-ta}かとおもうとattaches to た-form{V-te}いるかとおもうとattaches to て-form
Variant notes
- たかと思ったら — the spoken default, and the only one that comfortably takes a first-person discovery — 開けたかと思ったら空だった.
Notes
planned act does not fit, and no request or command can follow.
Related patterns
Similar
とたんに reports the second event as a consequence of the first, however unexpected; かと思うと requires it to land as an abrupt turn, most often the reverse (泣いているかと思うと、もう笑っている) — a smooth, expected continuation gives it nothing to jolt against (?座ったかと思うと、本を読み始めた).
Lookalikes
The 思う in かと思うと is nobody's stated opinion — the frame is frozen and takes no politeness or negation (×かと思いませんと), while と思う is a real predicate the speaker inflects at will (と思います, と思わない); learners read the first as "I think that…" and lose the reversal entirely.