I was walking down a narrow alleyway from a car park to High Street in Coleshill. An elderly man whom I didn't know was walking towards me. He smiled at me as we came close. I smiled back. Why was there this exchange of expressions? Presumably he felt, subconsciously, that he was in a dangerous position and wished to ensure that I meant him no harm. My returned smile meant that I meant that I had no evil intent and so we could each pass the other without further fear. It seems, incidentally, that it is actually quite difficult to frown at someone who is smiling at you. You have to make a real effort. And once you have smiled at someone it is, I would imagine, difficult to go on to attack them in an unprovoked way, unless you are a psychopath.

Smiling is a sort of challenge to the other person to smile back. It has to be used in a nuanced way, however, as smiling at everyone you see would probably get you locked up in a mental hospital. It is though is one of those things which obviously enables us to live socially without too much concern about our safety. It is not obvious, however, that it should work and it is not obviously rational, but we and other primates (Chimpanzees have 16 different sorts of smile - we have only 13) rely on this rapid form of non-verbal communication in default of a better way of expressing our intentions.

This year we have decided, unusually, to let one of the student houses to individuals rather than a pre-formed group. We were contacted by a Vietnamese who was in Birmingham and who decided to take a room. We have tried very hard to help her, granted that her English was not of the highest quality. Then we were contacted by e-mail by a French Erasmus student. She had seen pictures of the house on our web-site. We were in France at the time and our initial response was in French. Then we were contacted by a Spanish girl on the Erasmus programme, again by e-mail. We put her in touch with the other two. So we still had two bedrooms to fill. Sandra then took the lead in trying to fill the other rooms - obviously it benefits the tenants, as they all share the household bills. She put a notice on the University student site. She has been saying that we are ‘nice landlords' (although she has never even spoken to us) and that we responded to e-mails quickly. Since the notice has gone on, her recommendation of us has obviously worked wonders, as we have had lots of responses from people wanting rooms.

Why? Well obviously when faced with many similar properties on the university web-site, it is very difficult to decide which one to choose. There is a lack of data about the important things, such as - "Are the Landlords nice people?". Once an independent party has given you a good review, then that shifts the balance in your favour. Is it rational? Well not really. We could have paid her to do it, or she could simply be pretending that we are nice in order to get others to share the cost of living there with her. It just goes to show that, as the advertising industry knows very well, where there is almost no way of making a rational decision, we grasp at anything which can help us to make a choice, even if it is not very rational. I should add, of course, that we are very nice indeed.

And then there is the matter of Fred West's Cardigan. Fred West was a notorious serial murderer in the 70's. A psychologist giving a paper at a scientific conference asked those present if they would be willing to put on a cardigan which he produced. A lot of hands went up. Then he said that it was Fred West's cardigan and asked the same question. Almost no hands were raised. When people are asked if they would be willing to accept a transplant of organs from murderers and rapists, lots of people say "No".

Clearly we have a fear that we might catch something from the transplanted organ or cardigan, even though we know that it is quite irrational to think so. Or at least we know now. In the old days, by which I mean before the last 100 years, when we really did not know how things worked, we had all sorts of ideas as to what the different organs did. Falstaff speaks of the predicament that "a man of his kidney" was in. By which he meant a man of his temperament - in other words, the kidneys were thought to affect a persons character.