I am looking for ways to automatically assess the language register of a person's speech: formal, informal, ... or through some grading mechanism that would associate a 'score' depending on the person's level of language. Imagine Homer Simpson compared to John Steinbeck.
I've read about readability tests such as Flesch-Kincaid or SMOG but find their approach too simple. Counting words and syllables does not account for idioms, vocabulary, sentence structure,...
Is there something beyond comparing the speech with a list of simple words such as the Dale-Chall 3,000 Word List?
Edit: I would like to analyze the transcripts of the GOP and democrats debate and see if anything stands out in the way the candidates express themselves. I'm looking at different things, topic modeling, simple sentence metrics, ... . And Informality analysis seems to be an interesting path to follow and may help emphasize differences between the candidates. The fact that there is no 'settled' metric is all the more interesting since I'll to design and train the method. The paper from Mosquera and Moreda cited by Dominik is exactly what I'm looking for. Very grateful for all your comments and help