A while ago, there was this e-mail going around:

“Arocdnicg to rsceearch at Cmabrigde Uinervtisy, it deosn’t mttaer in waht oredr the ltteers in a wrod are, the olny iprmoatnt tihng is taht the frist and lsat ltteer are in the rghit pcale. The rset can be a toatl mses and you can sitll raed it wouthit pobelrm. Tihs is buseace the huamn mnid deos not raed ervey lteter by istlef, but the wrod as a wlohe.”

This was in fact was a test for something completely different (how fast an e-mail can travel around the globe), and these cited studies had never been done. People bought it up though as it did seem to be true. During my research for the phd I came across a study that looked at this phenomena and the results are as such: you can read the text with jumbled letters that are within the word boundary but with reduced reading speed. Your reading speed decreases more if the jumbled letters are at the end of the word, and even more if they are at the beginning (Rayner, White, Johnson, & Liversedge, 2006). You can see the results.
Rayner, K., White, S. J., Johnson, R. L., & Liversedge, S. P. (2006). Raeding Wrods With Jubmled Lettres. Psychological Science, 17(3), 192-193.