The human mind is a weird and wonderful creation. I've been learning recently how our brains automatically fill in gaps in our knowledge and embellish memories using imagination. Psychologists agree that this filling-in process takes place but they don't seem to have agreed on a name for it. I just realised that I have the word they need. It was invented 25 years ago by a 4-year-old boy.

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The word is prophicating and it was created by one of my sons. He noticed, very perceptively, that what his mother was confidently telling him was perhaps not entirely supported by the facts. He looked up at her and said, not accusingly but more with the air of a student learning a key lesson, "You're prophicating, aren't you!" The word has been part of the family vocabulary ever since.

My wife has a vivid imagination and a strong urge to teach. One result of the combination of these two gifts is a tendency to speak about details that she doesn't actually know herself. Retelling a phone conversation in which she has heard about a friend's new dog, she will gesticulate to demonstrate the exact size of the animal even though she has seen it only in her imagination. I have always considered my wife unusual but apparently this behaviour is more normal than I thought. We all do it to some extent and most of the time we can't see the join between imagination and reality.

The word prophicating is an attractive description of the imaginative filling-in process partly because of its allusions to three other words:

prophesying - speaking words that come not from the conscious mind but from divine or other inspiration

fabricating - making stuff up, telling lies

pontificating - speaking confidently and dogmatically

To prophicate is to speak from the imagination, believing it to be real. It sounds bizarre but it is, in fact, normal behaviour. This has profound implications for risk communication, indeed for any communication at all. We all prophicate, including experts on whom we rely for information about risk. The scientist is the high priest of the scientific age. Non-scientists are often called lay people. But we should not forget that scientists are human. Their decisions are influenced by their emotions and they prophicate like the rest of us. They do not have any special powers. Science is a method for evaluating hypotheses against evidence, not a religion.

When we receive communication about risk, we need to be alert. How much are the experts speaking from the evidence and how much are they prophicating?