Claude Shannon (of the information theory fame) did a similar research with his 1951 paper "Prediction and Entropy of Printed English". He used a particularly c

Claude Shannon (of the information theory fame) did a similar research with his 1951 paper "Prediction and Entropy of Printed English". He used a particularly clever idea, leaving out words or letters from English text, he then measured how accurately people could predict the missing text. And then used those numbers for statistical information-theoretical analysis to estimate the information density at about 9-11 bits (IIRC) per letter.