There's an internet rumor that I imagine most people are familiar with that usually goes something like this:

The phaonmneal pweor of the hmuan mnid, aoccdrnig to a rscheearch at Cmabrigde Uinervtisy, it denos't mtater in waht oredr the ltetres in a wrod are, the olny iprnoatmt tihng is taht the frist and lsat ltteer be in the rghit pclae. The rset can be a taotl mses and you can sitll raed it wouthit a porbelm.

Tihs is bcuseae the huamn mnid deos not raed ervey lteter by istlef, but the wrod as a wlohe. Amzanig huh?

I don't know much about the truth value of the counter claims, since I was just pulling some heresay out of my long-term memory, but the latter part is definitely something we can test. I slapped together a quick javascript applet to help, so any old text can be pasted in and shuffled about.

Short words make reading scrambled text a lot easier, because any word with less than four letters remains in its unscrambled form, and all four letter words merely have two adjacent letters swapped. English has enough short germanic words that you can get away with most of your words being some six letters or less, which keeps all of the letters from straying very far from their correct locations. However, if you scramble the words in more formal writing that tends toward longer words, I think it starts to break down. I'll go find the first two news stories that pop up on Google News and scramble their first paragraphs:

Wtih the srgtlgue oevr haelctrahe eteirnng an eevn tgheuor pshae, Prenidset Ombaa has hit btoh a milnotese and a seped bmup in his deul pusiurt of a moajr ohauverl of the ninota's miaedcl sstyem and a rietrbh of pvigsssorriem in Acriema. Husoe appoavrl of the liltsogeain Sradtuay eevn if Dmaeotcrs cluod mvoe it no freahtr--was a sgianl acmcpmilheosnt taht has eedlud pntdieesrs for daceeds. But the cosle vtoe and the extroneis it took to srucee a mojitray wree leadn wtih wnnirag snigs as the isuse moevs to the Stnaee. Eevn thoguh the Hsoue is a batosin of lesailbirm, the heltah crae oeruhval was a tgeuhor slel tahn etpecxed and the blil tnured out to be mroe ctearosvvine in its prcie tag, mroe liimted in the socpe of its gnoernvemt-run inuarcsne ooptin, and tihetgr in its rtnisitreocs on aotrobin funindg tahn mnay Drtacemos had hoepd

An Amry chpaialn aeksd mnoerurs Sanduy to pary for the aeucscd Frot Hood steohor, cianllg on tehm to fcous lses on why the tegardy hppeaend and mroe on hleping ecah oethr toguhrh "the vllaey of the sdaohw of dknarses." "Lrod, all tsohe anurod us sercah for mivote, sercah for maineng, serach for sitemnhog, soenmoe to bmlae. Taht is so fntrusriatg," Col. Farnk Jacsokn tlod a gourp of aobut 120 ppeole getehrad at one of the pos'ts chpael. "Taody, we psuae to haer form you. So Lrod, as we pary totgeher, we fcuos on tnighs we konw."

So go scramble some long-worded passages, show them to your friends, and convince them that not being able to read it indicates some kind of brain damage.