The last time I took a flight, I watched a funny-ish sitcom called Black-ish, about an African American family that has managed, against all odds, to become middle class and live in a posh neighbourhood.

The father, terrified of becoming "too white" and losing touch with what he thinks of as "Africa" (hopping around a drum dressed in tie-dyed sheets), nevertheless sends his son to a predominantly white school. On the boy's first day, the father is dismayed to hear he didn't give other black students "the nod".

"It's your duty to give 'the nod'," he admonishes. "Even in the most extreme circumstances we always find a way to let each other know: 'I see you, bro.'"

That made me think about the tricky inter- laowai (Caucasian) etiquette in China. To nod or not to nod?

Just because we're both in China and are vaguely the same colour, should I acknowledge other Westerners ("Mr Laowai-stone, I presume?") or should I studiously ignore them?

In my experience, there are two basic types of laowai: the "avoid eye-contact with similar-looking people at all costs; what are they doing here? This is my China, I discovered it" type, and the "dear similar-looking person, thank you for saving me, please let me speak English, let me speak many, many words and tell you everything I know about China" type.

For years, I belonged fiercely to the first category and found my match in eye-contact avoidance only in my friend L, who would shout, "Enemy at 12 o'clock!" whenever a beige-ish person hove into view. On trains and buses, in towns and on great walls, L and I would avoid "the only other white in the village" as if he were insulting us deeply merely by being on the same continent.

But once even we had to get over ourselves and yield to a Livingstone-style greeting. In a crowded temple square in Lhasa, Tibet, a ginger-haired German, burned to a cinder and looking like one of those cartoons of a guy dragging himself through the desert croaking "water, water", came up to us and whispered in a voice rusty from disuse that he had driven to Tibet from Shanghai on a motorbike. Without the requisite permission, he had hidden in his helmet at innumerable police roadblocks and let his Chinese girlfriend do the talking - and the bribing.

He was so sick of Putonghua, so starved of a European tongue and beige faces (forgetting his own face was now burgundy) that we had to take pity on him and have a chat - or rather, listen to him raving on and on.

Nowadays, I often do the nod. In fact, I initiate it. With a smile!

And sometimes, the laowai nods back.