Déjà vu

The term is French for "already seen"; it's only been around since the 1870s in a formal sense but no doubt everyone from pre–historical times on has experienced it.

Last year psychologist Alan Brown of Southern Methodist University in Dallas published a book on the subject entitled "The Déjà Vu Experience," in which he took a look at prevailing theories as to the cause of the phenomenon.

He noted four main theories holding sway at present:

1) The experience is simply a misfiring in our brain cells, somewhat akin to a muscle spasm.

2) Information travelling from our eyes, ears and other sensory organs takes a number of routes to the regions in the brain where it's processed. If one track is blocked for a fraction of a second, we may not be able to tell that the duplicates arrived milliseconds apart, rather than months.

3) Implicit memory, which refers to the fact that our senses gather information of which we are unaware that can influence our later reactions without us knowing why we have these reactions.

4) The brain may make connections between a current experience and fragments of implicit memory lurking in our minds, bits which are similar but not precisely the same.

That's all well and good but it seems to me Brown omits a far more likely cause: that all experiences — which we arbitrarily divide into past, present and future — exist permanently.

We simply move, for the most part, in one direction through them, giving each of us a sense of a beginning and an end and a "flow" of time.

But as Michael Crichton put it, "Time doesn't flow; we flow."

Once in a while there's a hiccup, a jammed gear in the machine, and we seem to run an experience through the projector a second time.

Or a third.

If we could get a better handle on this we could travel freely in time.

Alas, that will be the among the pleasures only of those who come after us.

Unless someone really smart gets busy really soon.

[via Stephen Pincock and the Financial Times]