The difference in error rates is in large part due to the to the difference between dictated speech and spontaneous, informal conversational speech. Switchboar

The difference in error rates is in large part due to the to the difference between dictated speech and spontaneous, informal conversational speech. Switchboard (http://www.ldc.upenn.edu/Catalog/CatalogEntry.jsp?catalogId=LDC97S62 http://www.ldc.upenn.edu/Catalog/CatalogEntry.jsp?catalogId=...) is a set of telephone conversations between two people. Speakers tend to say a lot of "ums", abruptly restart an utterance in progress, talk past the telephone handset, etc. Dictated speech, especially when speakers know they're talking to a computer, has less acoustic and linguistic noise.