"Sam Vimes could parallel process. Most husbands can. They learn to follow their own line of thought while at the same time listening to what their wives say. And the listening is important, because at any time they could be challenged and must be ready to quote the last sentence in full. A vital additional skill is being able to scan the dialogue for telltale phrases such as "and they can deliver it tomorrow" or "so I've invited them for dinner?" or "they can do it in blue, really quite cheaply."