Actually astonishing that German is AFAIK the only language with capitalization of substantives. Reading this question, I remembered this little experiment, TRY to read it! :)
inner letters mixed
I cnduo't bvleiee taht I culod aulaclty uesdtannrd waht I was rdnaieg.
Unisg the icndeblire pweor of the hmuan mnid, aocdcrnig to rseecrah at
Cmabrigde Uinervtisy, it dseno't mttaer in waht oderr the lterets in a
wrod are, the olny irpoamtnt tihng is taht the frsit and lsat ltteer
be in the rhgit pclae. The rset can be a taotl mses and you can sitll
raed it whoutit a pboerlm. Tihs is bucseae the huamn mnid deos not
raed ervey ltteer by istlef, but the wrod as a wlohe. Aaznmig, huh?
Yaeh and I awlyas tghhuot slelinpg was ipmorantt! See if yuor fdreins
can raed tihs too.
inner + first letter mixed
I dloucn't ebeilve taht I lcuod utllaacy tsnredanud awht I was
irdenag. sUnig hte eidbcrline poewr of the umhan nimd, ccrdiaong to
aecrersh at biCagmdre eivUnirsty, it esdon't eattmr in hawt droer the
teltres in a rwod are, the lnoy ropamintt nthig is that hte rfsit nad
alst eltetr be in the hgrit aclpe. The rest acn be ttoal mses and oyu
acn tilsl aerd it ouithwt a rebplom. hiTs is ecuasbe hte muahn mind
does ont ared every leettr by iletsf, but hte orwd as a hlwoe.
maiAzng, uhh? Yeah nad I lwyaas hugthot lisneplg was mprnotait! eSe if
oyur nridfes acn raed iths oto.
all letters mixed
I onlucd't ieebvel ttah I udloc talyulac rsddetanun hwat I swa
radgeni. sngiU eth inrdebelic rweop fo hte nmauh imdn, dorcincga ot
arceehsr ta meaiCrgbd yvisUntier, it deson't ramtet in athw rored eth
erlttes ni a rwod rae, hte noyl atomirnpt nhgti si ttha hte tsfir and
last letert eb in het girth leacp. eTh sret anc be tolta ssem dna ouy
cna litsl eard it wohutti a elrpomb. ishT is secbaeu het mahun mnid
dose tno aerd verye leettr yb efsilt, btu hte orwd sa a leohw.
agzmnAi, huh? Yhea nda I awlyas utgtohh lgniespl aws optnrimta! eSe if
uoyr resfdin acn eadr siht oto.
I couldn't believe that I could actually understand what I was reading. Using the incredible power of the human mind, according to research at Cambridge University, it doesn't matter in what order the letters in a word are, the only important thing is that the first and last letter be in the right place. The rest can be total mess and you can still read it without a problem. This is because the human mind does not read every letter by itself, but the word as a whole. Amazing, huh? Yeah and I always thought spelling was important! See if your friends can read this too.
It works better with text in your native language, because your are more used to look/shape of words. It also shows clearly how important the first & last letter is. Its a very good proof to me that the capitalization in German is highly useful, kind of syntax-highlighting ;)
It also make Speed Reading much easier to me, its not so easy to mix up a adjective/participle with a substantive, you can better scan the text for keywords (mostly substantives) and its easier to localize redundant fill words (e.g. of the,...)
Here some further links I had on this interesting topic:
http://www.ruediger-weingarten.de/Texte/Capitalization.pdf also mentioning the Bock study from Oregon answer
Maybe the English studies you were looking for, but behind pay wall
Someone should write a script with auto capitalization of all English substantives in a webpage. On my way to the patent office...