1. A computer-implemented method of determining a difficulty level of a text, comprising: determining with a processing system a number of cohesive devices present in a text; determining with the processing system a number of cohesive devices expected in the text, wherein determining the expected number of cohesive devices includes: for each sentence in the text having a preceding sentence in the text, determining a total number of words in that sentence and a sentence preceding that sentence to generate a sentence pair total; determining a sum of the sentence pair totals; and determining the expected number of cohesive devices based on the sum of the sentence pair totals; calculating with the processing system a cohesiveness metric based on the number of cohesive devices present in the text and the number of cohesive devices expected in the text; and identifying a difficulty level of the text based upon the cohesiveness metric.