[lttlrck]

If I listen to the radio (speech) and then start to read and try to simultaneously listen to the radio it becomes incomprehensible. Quite weird.

[wh313]

Funny, it still works for me. Could it be an attention thing instead?

[pharke]

Probably has more to do with how you process written vs audio information. Richard Feynman had an anecdote about discovering that he couldn't read and count in his head at the same time but others could, turned out the person who could counted in his head by visualizing the numbers rather than 'hearing' them in his inner monologue which allowed him to continue reading.