And then, I think it was perhaps in 2005, I got a letter. So many of my... I don’t know what to call them, house calls, neurological adventures, have come, as they came for Sherlock Holmes, when there’s a knock at the door, or a letter arrives. Of course, for me it can also be a phone call, which I don’t think it could be for…  I don’t think the telephone ever exists in the Sherlock Holmes…

Interestingly, of course, the Holmes stories started to be written at the end – the long novels – at the end of the 1880s. They were written into the mid 1920s, by which time telephones did exist, but Conan Doyle remarks this in his preface to the collective works, that you cannot date them, and in fact, they are all in a changeless London of the 1890s. Where was I? I’ve lost my train of thought. Yes, so I received a letter from someone whom I had met nine years earlier. Her husband was an astronaut, Dan Barry, and at that time – and still I was – very, very interested in... in astronauts, and the shuttle, and spaceflight. I was going to write about this, and in a way which I still find heartbreaking, my big notebook, which was full of notes I took at the multiple launches and landings, got lost. Actually it got stolen. It was in an attaché case with other things of mine, and it got... there was a break-in to a hotel room in London and it was stolen – useless to the thief, disabling for me.

But anyhow, it was at a launch party for Dan Barry. He wasn’t there, of course, because he was preparing to go in the capsule, but his wife, Sue, was there, and... I don’t know how we got on to this, I think she came up to me and said, 'You’ve been looking at me'. I said, 'No, I haven’t,' and she said, 'Yes, you have'. She said, 'You think there’s something askance with my eyes'. Well, she was right, I did think so. She said... she says, 'Cosmetically they’re perfect, but they are not quite in alignment, are they? And I said, 'Well, now you mention it I agree, they are not quite in alignment'. And she told me then that she had been born with a squint, or strabismus, cross-eyed, that there had been surgery to correct vision when she was two, and again when she was four, and again when she was seven, or whatever, but functionally the eyes were independent. Both were good eyes. Sometimes, if people have a squint the brain suppresses information from one eye, which becomes effectively blind. This hadn’t happened with her. Both eyes were good, but she was either using one eye or the other, but never both of them together. And this meant for me, that she did not have stereoscopic vision, which depends on using both eyes together, and the brain’s... computation of distance from the disparity between these two images. And I asked Sue... I asked Sue whether she could imagine stereovision? And she said, 'I think so'.  She said, 'I’m a professor of neurobiology'. She said, ‘I’ve read Hubel and Wiesel’s papers'.  Hubel and Wiesel had written groundbreaking papers about the elementary vision, including stereovision, in the 1960s, and she had, you know, she had studied these when she was in college. She said, 'I think I can imagine it'. I said, 'Okay'.

 
Nine years later I got a letter from her, in which she recalled this conversation, and her saying that she could imagine stereovision, and she said, 'I was wrong'. And she went on to say that in fact – and she described in detail how it had happened – in fact, to her own amazement, she had acquired stereovision in her 50th year.