"Very," I tell her. "And I bet you use it more than you think."
These days, all methods of communication are used just to try and keep contact with family and friends - and I mean the ones you live with - never mind the emails to your sister in Oz, the SMS chat to girlfriends, Christmas cards to ex-colleagues, letters to your Granny, texts to your lover and phone calls to your mum.
I thought back to Sunday. As I got up in the morning, I saw a note under my bedroom door; it was from my daughter who wanted me not to wake her as she'd had a late night. Going downstairs, I noticed a pair of men's boots in the kitchen. More communication, intentional or not, telling me that her boyfriend had stayed over. Further "objects of reference' in the kitchen told me my son had had a pizza and a few beers and the scrawl on the chalk board was asking if I would wake him if I was going shopping. I communicated with him by banging on his bedroom door and interpreted the grunts and groans as meaning would I wait five minutes while he got dressed. As I waited I watched the news, listening to and watching correspondents from across the globe transmitting events, feelings and analysis through pictures and sound.
Jim was ready so off we went, obeying all the symbols and signs en route.
In a happy mood, I began to sing. Jim turned on the radio. Nothing more needed to be said. At the market car park, I indicated with a nod and a coin that Jim should go and get the ticket while I listened to the rest of The Archers. We shuffled around the busy market, observing other shoppers'
body language so that we didn't actually bump into anyone. It was noisy so I signed to Jim: "Tea?" He nodded his assent. "You get it mum," he shouted.
"I'll just check out these DVDs". I followed the smell of bacon to the tea stall but inevitably got lost amongst the shoppers, signs and posters.
Luckily we both had our mobiles on and soon met again under the clock - the traditional meeting place. My daughter texted me: "Get me stripey sox plz."Although she'd taken all the vowels out of "please" I knew what she meant. The man at the sox stall spoke little English but we made the transaction using gestures. Jim tapped his watch and nodded towards the car park. It was time to go.
"Total communication - is it easy to learn?" asked my visitor. "Oh yes," I said, "most people do it without even thinking!"
Maria Corby is deputy head of a special school for pupils with severe and multiple learning difficulties. She writes under a pseudonym