11. A non-transitory computer-readable storage medium for measuring a user's comprehension of subject matter of a text, the computer-readable storage medium comprising computer executable instructions which, when executed, cause a processing system to execute steps comprising: receiving a summary generated by the user, the summary being a constructed response that summarizes a text; parsing the summary with the processing system to identify a number of sentences contained in the summary and to identify in the summary a plurality of multi-word sequences; processing the summary and a reference summary with the processing system to determine a first numerical measure indicative of a similarity between the summary and a reference summary, the reference summary having been designated as representative of the subject matter of the text; processing the summary with the processing system to determine a second numerical measure indicative of a degree to which a single sentence of the summary summarizes an entirety of the text; processing the summary and the text with the processing system to determine a third numerical measure indicative of a degree of copying in the summary of multi-word sequences present in the text; and applying a numerical model to the first numerical measure, the second numerical measure and the third numerical measure to determine a score for the summary indicative of the user's comprehension of the subject matter of the text, the numerical model including a first variable and an associated first weighting factor, the first variable receiving a value of the first numerical measure, a second variable and an associated second weighting factor, the first variable receiving a value of the second numerical measure, and a third variable and an associated third weighting factor, the third variable receiving a value of the third numerical measure.
14. The non-transitory computer-readable storage medium of claim 11 , wherein the computer executable instructions cause the processing system to execute the steps comprising: processing the summary with the processing system to determine a fourth numerical measure indicative of a number of discourse markers included in the summary; and applying the numerical model to the fourth numerical measure to determine the score for the summary, the numerical model including a fourth variable and an associated fourth weighting factor, the fourth variable receiving a value of the fourth numerical measure.