The C-test as a measure of comprehension knowledge.

Baghaei, P., & Tabatabaee, M. (2015). The C-Test: An Integrative Measure of Crystallized Intelligence. Journal of Intelligence, 3(2), 46-58.‏

This is a short and clear paper about the C-test, a closure test.  In classical closure tests, every n-th word in the text is omitted.  The child is required to complete the missing words.

The C-test is a new kind of closure test.  The test consists of four to six text paragraphs.  In each paragraph, beginning from the second word in the second sentence, the second part of each second word is omitted.  There are usually 20 to 25 part words in each paragraph.  In order to give the child enough context, the first and last sentence in each paragraph remains intact.  For each correct word that is completed the child gets one point.

Here is an example of a C – test paragraph:

If you were to ask most people who Charles Darwin was, many of them would reply that he was the man who said that we were descended from monkeys. They wo___ be wr___. Darwin d___ no mo___ than sug___ the possi___. What h___ said, a___ proved b___ thousands o___ examples, w___ that ov___ millions o___ years ani___ and pla___ have cha___. This he called evolution.

What does the test measure?

The test measures verbal ability in the first and second language.  Scholars argue that the processing done in this test resembles natural language processing.

The test also measures integration of knowledge about the context (general information), semantic knowledge (knowledge about meaning and content), grammatical knowledge, morphological knowledge (knowledge about the meaning units that make up words), lexical knowledge (vocabulary), and orthographical knowledge (spelling rules).

There's no doubt this test is affected by reading and reading comprehension skills, as well as by fluid ability and short term memory.  The larger the segment of text the child reads in order to complete a word, the higher his score on the C-test.

Difficulties on this test can arise from hasty closure (ending a sentence before it ends), narrow focus (using only the immediate context), wrong spelling, mismatch of singular and plural forms, choosing a wrong word out of a right category, relying too much on genera knowledge (completing according to general knowledge and not according to the text's requirements), inattention to grammatical nuances, automatic completion using highly frequent words and difficulty retrieving lexical items.  It's harder to complete words in long and complex sentences, since it's more difficult to understand these syntactical structures and they load working memory.