在一次长途飞行中，他在信手圈圈点点之后发现，即使没有极端的种族歧视，现代城市中常见的极端种族隔离现象也可能出现。
On a long flight , his doodles with noughts and crosses convinced him that the extreme racial segregation often seen in modern cities could arise without extreme racial prejudice .
圈圈点点