Perhaps you are impressed by the idea of young children being taught good manners, or perhaps you wonder if there is toilet paper stuffed inside that beautifully iced cake.

Besides, who defines good manners? Often young children are told to look at adults when spoken to but, as one of my young black clients said: "If I look at my father when he's scolding me, there'll be trouble." One person's act of politeness is another's insolence.

Eye contact is one of those behaviours that perfectly illustrates the occasional complexity of manners. Research shows that when being taken to task, most women will make longer, more frequent eye contact to gauge the situation or even to placate, whereas men tend to look away more. In a bar you might see a table of women looking at each other as they talk, and a group of men at the bar all staring at the opposite wall while they swap stories. Who's acting appropriately - the people looking or the people looking away?

People who feel shame often avoid eye contact, which is not just appropriate but perhaps an evolved behaviour. My Labrador Jack will look down or away when he is chastised for wolfing down the newly baked loaf of banana bread or an entire slab of butter.

What is regarded as polite practice also changes over time. For evidence, look at Hunting Lice by Candlelight, painted by Andries Both in the 1600s, which depicts what was then common practice of people removing head lice from each other's hair.

When we bemoan the lack of manners in today's world it is first of all important to place manners in their cultural and historical contexts.

Nevertheless, we don't have to be too politically correct. Some behaviours are just plain impolite and rude: couldn't-be-bothered shop assistants, name-calling customers, aggressive drivers, passengers who throw litter out of their cars, or children who don't greet you or thank you. Most adults are particularly offended by disrespectful children and teaching good manners is of great concern to parents. After all, it's one thing to laugh off a rude adult, but another to swallow the idea of a child set on a lifetime-long path of disrespect. Good behaviour is important to adults because it demonstrates that we have done our work well and that the golden age (that is, whatever age it was when we were children!) is not yet over.

Good manners are vital for two reasons: they are a useful social skill that opens doors and earns acceptance from others, and they tell others that we have noticed them.

Manners are also relatively easy to teach. Children respond well to frequent verbal reminders. Some fundamental things to be firm about: greeting and saying goodbye when visiting; saying please and thank you, including to those with perceived lower social status such as waiters; offering a seat to an older person; not littering; waiting your turn and not pushing or grabbing; and being respectful of other people's places, from homes to restaurants.

Teach etiquette in a calm tone, preferably before the fact, rather than in a heated or embarrassing situation. Be specific: tell your child to "say thank you" rather than to ''behave politely". And remember that some behaviours are age-appropriate, so that it is unrealistic to expect a two-year-old to sit quietly for long periods in an upmarket restaurant.

Remember also the difference between form and substance, between a homely cake and the fancy one filled with toilet paper. My friend's son left his well-mannered school after one year because she soon discovered a rigid, intolerant environment that was not respectful of her son's needs. Ambrose Bierce, a US writer and satirist, described this form of politeness as 'the most acceptable hypocrisy'.

Don't be fooled that true respect is skin deep. A normal teenager will sometimes forget his manners when he feels guilty, but in the same situation a psychopath will look you straight in the eye because he doesn't feel any guilt.

Value and teach good manners, not to create a polite facade, but to demonstrate our regard for others and to help build a more thoughtful, helpful society.

• Ancer is a Johannesburg-based psychologist