One of psi-sceptics' most popular arguments that anecdotal evidence can't be relied on. If you agree with that, you can ignore much of the case for psi - the whole human experience bit. With that out of the way, the experimental data can be waved away on the grounds of methodological flaws and wishful thinking.
I've been reading up on neuroscience recently, and started to notice how often the Phineas Gage story crops up. This is the nineteenth century railway worker who miraculously survived an explosion in 1848 that sent an iron bar 43 inches long and more than an inch in diameter right through his skull. Although Gage suffered massive damage to his frontal lobes, he remained conscious and eventually recovered, still able to function normally in most respects (although it did for him in the end - he died 11 years later). However he underwent a major personality change - having been a solid, dependable sort he now became roguish and disreputable, given to drinking and swearing, to the extent that his friends no longer knew him as the man he had been.
The story is told to demonstrate the dependence of the personality on the brain, and, more specifically, the frontal lobe as the seat of emotion. It's a colourful piece of evidence given in support of the orthodox view that the mind is what the brain does. If the structure of the brain is compromised, then so too will the personality be.
The case is big in popular culture - apparently there are rock bands named after him. It's also much referred to in academic books about cognitive psychology and neuroscience: I did a quick search on Questia and came up with 122 mentions. I can't tell in detail what each mention there consists of, but from the excerpts the majority seem to raise it as demonstrating the dependence of personality on the brain. And it continues to be influential - for instance it's a key piece of evidence in Damasio's controversial recent book Descartes' Error, which proposes that rationality is largely guided by emotions.
But how true is the story? According to author and psychologist Malcolm Macmillan, who did some sleuthing, the before-and-after contrast has been greatly exaggerated.
The main testimony comes from Dr John Harlow, the physician who attended Gage an hour after the accident and more or less put him back together. In 1868, eight years after his patient's death, he wrote:
The equilibrium or balance, so to speak, between his intellectual faculty and animal propensities, seems to have been destroyed. He is fitful, irreverent, indulging at times in the grossest profanity (which was not previously his custom), manifesting but little deference for his fellows, impatient of restraint or advice when it conflicts with his desires, at times pertinaciously obstinate, yet capricious and vacillating, devising many plans of future operation, which are no sooner arranged that they are abandoned in turn for others. His mind was radically changed, so decidedly that his friends and acquaintances said that he was 'no longer Gage.
Yet Harlow said little about any of this when he first publicly talked about the case, when Gage was still alive. In 1850, two years after the accident, a Harvard professor of surgery stated that he was "completely recovered in body and mind", making no mention of any personality change.
In subsequent accounts by other writers Harlow's later testimony was embellished. Gage was now said to have become a drunkard and a boastful exhibitionist, as well as suffering an absolute lack of foresight - all unmentioned by Harlow. In fact most of what has been said about Gage subsequent to his physical recovery, Macmillan says bluntly, is "fable".
Coincidentally, I've been reading Marilynne Robinson's excellent Absence of Mind , an attack on the view of humanity represented in what she calls the "parascientific literature" of Dawkins, Wilson, Pinker, Dennett, etc. (She's actually a novelist - not one I've read, but after this I'll certainly be checking out her fiction as well). On the subject of Gage she asks whether it is really so remarkable that a man who has had a crowbar pass through his brain should not start to act in ways that other people find less than reasonable.
Are we really to believe that Gage was not in pain during the years until his death? How did that terrible exit wound in his skull resolve? No conclusion can be drawn, except that in 1848 a man reacted to severe physical trauma more or less as a man living in 2009 might be expected to do...
(Actually comic writer Rich Hall makes pretty much the same point, in a lol way, in a sketch in Things Snowball. I'd quote from it, but think I threw the book out because I kept reading it when I was supposed to be working.)
As for the attention the story gets from neuroscience, Robinson says, "It's as if there were a Mr. Hyde in us all that would emerge spluttering expletives if our frontal lobes weren't there to restrain him."
Anecdotal evidence - that's to say, reported human experiences - are absolutely valid in scientific discourse. Surely most scientists accept this - psychology and medical science in particular wouldn't get far without it: it's just in anti-psi writing that it's so suspect. What matters is that a story be properly validated. That's not the case here, and it's interesting to see such a key element of the materialist worldview being illustrated by a story with such slender foundations.