A BBC series is asking influential figures around the world about the defining moments in their life.
Lessing is a three-time Booker Prize nominee
Author Doris Lessing is one of the most respected names in literature. Her most famous books include The Grass Is Singing and The Golden Notebook. In 2001 she won the David Cohen literature prize in recognition of her lifetime's achievement.
I was probably about 13 or 14 - a very brash and pert white girl in a mission down in what is now called Mutari.
And I was chattering away, chatter chatter, showing off to some men who I now see were probably not as old as I thought they were then.
And they listened to all this chatter and then one of them said to me, "You see," he said, "you are very young, and I am very old".
And this was like a slap across the face.
And I know it doesn't sound important but it changed me completely in certain of my attitudes to the blacks.
I mean, don't forget how I was brought up - I was brought up inside the old Rhodesia.
It was the wonderful dignity of it and the sense of it, and the way I was very gently put in my place with great humanity and humour.
Yes, it changed me.
Defining Moments will run until 23 July on BBC World Service's World Today programme. You can also read people's recollections on BBC News Online.