Little Green Footballs' commenter Bordm contributes this to a discussion about a pretty cloud.
fi yuo cna raed tihs, yuo hvae a sgtrane mnid too. Can yuo raed tihs? Olny 55 plepoe out of 100 can.
i cdnuolt blveiee taht I cluod aulaclty uesdnatnrd waht I was rdanieg. The phaonmneal pweor of the human mnid, aoccdrnig to a rscheearch at Cmabrigde Uinervtisy, it dseno't mtaetr in waht oerdr the ltteres in a wrod are, the olny iproamtnt tihng is taht the frsit and lsat ltteer be in the rghit pclae. The rset can be a taotl mses and you can sitll raed it whotuit a pboerlm. Tihs is bcuseae the huamn mnid deos not raed ervey lteter by istlef, but the wrod as a wlohe. Azanmig huh? yaeh and I awlyas tghuhot slpeling was ipmorantt! if you can raed tihs forwrad it.
I remember this research coming out. There seems to be some doubt as to its origin. Matt Davis, who works at the MRC Cognition and Brain Sciences Unit at Cambridge University, says no-one at Cambridge is responsible and that it may in fact date back to 1976 and a PhD by Graham Rawlinson at Nottingham University.
Davis also shows that it's not as simple as stated (is it ever?), that certain transpositions make it very difficult indeed to work out the meaning, especially if the transposition makes a new word (see the example below). And it doesn't work for all languages; for instance, Hebrew.
This may reflect a interesting property of the Hebrew writing system. Since vowels are not written in the text, there is a lot less redundancy in written Hebrew. It may be that readers are already using some inference processes to work out what words are written, the extra load added by jumbling letters creates an additional, excessive level of difficulty. It's also possible that written words are more confusible in Hebrew - that is, many more words are like "salt" and "slat" in which letter transpositions create other words.