Several researchers have claimed that “morphological instruction” is an effective way to improve students’ vocabulary and reading proficiency (Carlisle, 2010; Nagy, Berninger, & Abbott, 2006).
The theory is that once you know the parts of words (prefixes, roots, suffixes), you will be able to “transfer” your knowledge of morphology to learn new words. A bigger vocabulary will in turn improve reading comprehension.
The proposed relationship goes something like this:
Morphological Instruction (Latin/Greek roots, affixes) –> Vocabulary –> Reading Comprehension
It’s a nice little theory. The problem is that it assumes that teaching kids word parts will result in them actually using that knowledge to build their vocabulary.
There are lots of studies of morphological instruction, and they all roughly find this:
(a) Kids given morphological instruction do well on morphology tests, such as identifying the meanings of root and prefixes.
(b) These same students also do well on the vocabulary words that are used in the training, so-called “taught” words.
(c) But trained students do NOT do better on tests of new vocabulary words or reading comprehension tests.
When you look at meta-analyses of studies of morphological training, you’ll often see a small but significant effect on “vocabulary.” The problem with this finding is that the researchers usually conflate test scores on taught words with scores on transfer words.
It is no surprise that when you teach vocabulary to Group A but not to Group B, Group A will do better on a test of those words (although not necessarily on reading comprehension).
That’s not the claim morphological instruction makes, however. It isn’t just supposed to help kids learn taught words, but figure out new, transfer words.
It doesn’t. The results of Baumann, Edwards, Font, Tereshinski, Kame’enui, and Olejnik (2002) are typical. Baumann et al. gave morphological instruction to a group of middle school students for 10 hours. They tested the kids immediately after the training, and then five weeks later. Students were tested on morphology, the taught words, and the transfer (new) words.
What did they find? The morphology group did much better than the control group on tests of morphology. The morphology group also did better on the taught words, again with large effect sizes* (d = .81).
But on the transfer words, the story was different. On the immediate post-tests, the morphology group did moderately better than the controls (d = .49), but a little over a month later, there was no difference (d = .05).
The results of morphology training are similar to those of phonics instruction. You get a big bump on the skill taught (morphology, phonics), but a small and fading one on what we actually care about (vocabulary, reading).
More to follow on morphological instruction in a later post.
*= Effect sizes (here, Cohen’s d) measure the differences between groups in (fractions of) standard deviations. An effect of .20 or less is generally considered small, .50 moderate, and .80 and over large.
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