Can we measure the effectiveness of ‘morphology instruction’?

MorphologySpelling

19 Sept

In this blog post, I take a look at a 2024 review and meta-analysis by Colenbrander et al. exploring the effectiveness of morphology instruction. I conclude that ‘morphological instruction’ encompasses such a range of approaches that conceptualising it as a single entity is unlikely to lead to practical insights for literacy educators.

Morphology as an instructional tool

I really enjoy using morphology (the study of word structure) as a tool for teaching literacy. It lies at a fascinating intersection between phonology (the sound systems of languages), semantics (meaning) and orthography (spelling), and it has close links to vocabulary and etymology (word origins).

I’ve designed and used lots of materials that have a strong emphasis on morphology, and I’ve personally seen adolescent students really ‘take to’ the approach by using word sums and morphological matrices. So, I was keen to read this paper by Colenbrander et al. to find out about the latest research on morphology instruction, and whether there were any insights into the best ways to implement it.

It turns out that there’s an awful lot we still don’t know – and this paper made me think more deeply about why drawing conclusions about morphological instruction is tricky.

Why morphology instruction should work

There are many reasons why morphology instruction should have a positive impact on reading, spelling, vocabulary and comprehension.

English has a morphophonemic spelling system, which means that spellings are not governed purely by sounds, but are also influenced by morphemes (meaningful word-parts such as prefixes, roots/bases and suffixes). For example, the suffix <‑ed> can be pronounced as /d/ (wailed), /t/ (laughed), or /ĭd/ (waited). Explaining to students that this variation in pronunciation does not affect the spelling of the past tense suffix <‑ed> should help them to spell it correctly. And, from a reading perspective, it should help them to connect the <‑ed> on the page to the word’s pronunciation and its meaning.
Individual morphemes contribute to the meaning of words. For example, if a word begins with the prefix <re‑>, it probably links to the notion of doing something again (e.g. refill). If students are taught (and retain) the meanings of morphemes, it ought to help them to figure out the meaning of unfamiliar words that include the taught morphemes.
Following on from the point above, learning about morphology could be particularly useful for English because it has many words that are derived from Latin, and these words often have bound bases. Bound bases are morphemes that can’t be used as words on their own, so they can be hard to spot, but they contribute a lot to the meaning of words. For example, <rupt> (meaning ‘break’ or ‘tear’) is not a word on its own, but it contributes to the meaning of many words e.g. erupt, interrupt, rupture, disrupted. Explicitly drawing attention to these word-parts should help students to read, spell and understand words that share the same base.
Logically, if morphology helps students to understand the meanings of words, it ought to improve comprehension, which relies on understanding the meaning of individual words (among many other things).
There may also be a wider benefit of giving students a new ‘word attack’ strategy to decode unfamiliar words by identifying morphemes. For example, if a student spots a known prefix and suffix, they can then focus on decoding the base.
Many adolescents who struggle with literacy are frustrated at what they perceive to be the irregularities of English spelling. Morphology can explain many of these seeming irregularities (e.g. double letters, dropped <e>, <y> changing to <i>, and syllable spellings such as <tion> and <cian>). Teaching them how the writing system actually works may help students to develop a more positive attitude to reading and spelling.

So, there are lots of reasons why including morphological instruction in literacy interventions seems a good idea. But what does the evidence say?

What does the meta-analysis show?

A meta-analysis brings together research from lots of studies into one big statistical analysis, to try to provide an overview of what the research can tell us about a certain topic.

This review and meta-analysis by Colenbrander et al. combined the data from 28 studies. The authors concluded that “this meta-analysis provides evidence that morphology instruction is effective for improving reading and spelling outcomes, particularly for words that are directly taught”.

So far, so good. But it turns that this meta-analysis can’t tell us much more than that. As the authors admit: “current research seems to indicate that morphology instruction works, but provides very little clear information regarding for whom it works, under what circumstances, or what features make it effective”.

Let’s take a look at why we know so little. There are several reasons why it was difficult to draw detailed conclusions from the meta-analysis. Below, I’ve categorised the difficulties into three main areas:

Difficulties in assembling data
Difficulties defining morphological instruction
Difficulties measuring the impact of morphological instruction.

1. Difficulties in assembling data

There were some limitations that relate to the data that was included in the meta-analysis:

Meta-analyses in education research inherently have to contend with combining data from diverse studies that used different approaches, different methods of assessment and different participants (listen to this ERRR podcast episode for an interesting and accessible discussion on this topic).
The authors also mention issues due to a lack of information about certain aspects of the studies, including dosage (how much time was devoted to the intervention), fidelity and the content of the interventions.
There were limits in terms of the number of studies that included certain subject groups – for example, only three studies investigated ‘beginner readers’, so it was difficult to draw clear conclusions about effectiveness for pupils of different ages. (This meta-analysis only included students within their first seven years of formal schooling, so – unfortunately from my perspective as a secondary practitioner – adolescents weren’t included.)
The meta-analysis showed bigger effects for trained words (for reading and spelling outcomes) than untrained words, and some evidence of transfer to untrained words (for spelling outcomes). (‘Trained words’ are those that were taught during the intervention, and ‘untrained words’ were not taught.) However, the authors state that “the majority of studies did not distinguish between trained and untrained words in their outcome measures”, so many studies weren’t included in this part of analysis. This lack of data is a problem because a fundamental reason for teaching morphology is that learning should transfer to new words.

2. What is morphological instruction?

Another reason that the meta-analysis did not show much about how to teach morphology is that morphology inherently overlaps with phonology, semantics, orthography and etymology. This means that it can be taught in many different ways, including a meaning-based approach, a spelling-rule approach or an etymological approach – and it can’t be fully separated from phonics either. So, there are clear difficulties with defining ‘morphological instruction’ within an intervention.

The authors’ criteria for inclusion was that the “primary aim of the intervention/instruction must be to teach one or more aspects of morphology (e.g. prefixes, suffixes, bases/roots, derivations, inflections) in oral and/or written language”. The studies that contribute to this analysis have a variety of intervention methods, ranging from Structured Word Inquiry to spelling-rule approaches, a focus on multisyllabic word reading, and some oral interventions.

With such a range of intervention approaches, it’s debatable whether it’s sensible to think of ‘morphological instruction’ as a single entity at all, and it’s perhaps unsurprising that the meta-analysis reveals little about exactly what works.

One issue mentioned by the authors is the proportion of the instruction that is devoted to morphology in these studies. Although they included only studies in which morphological instruction constituted 50% or more of total instructional time, many of the interventions included several types of instruction, and this made it difficult to identify the ‘active ingredients’.

3. How do you measure the impact of morphological instruction?

Measuring the impact of a morphological intervention is tricky – after all, what gains are expected, in what activities, and compared to what?

Perhaps of some concern is that the meta-analysis showed that experimenter-designed reading and spelling tasks showed significant positive effects of morphology instruction, but standardised reading and spelling tasks and reading comprehension tasks did not. The lack of an effect of morphological instruction on standardised tests raises the question of what we expect successful morphology instruction to look like, and I discuss that more below.

Assessments should reflect the goals of instruction

To measure the effectiveness of morphological instruction, we need to know what it’s aiming to achieve, and we need measures that can test whether that outcome has been achieved. However, the goal of instruction will depend on the age and stage of pupils.

For example, a morphological intervention for very young children who are still learning basic decoding would presumably teach children to use information from common affixes (such as the suffix <-s>) to help them to decode and possibly spell simple words. A basic reading and spelling assessment might be appropriate to assess progress.

In contrast, pupils with a competent decoding level might be taught to use morphological information to help understand the meaning of unfamiliar words and assist the spelling of long words. Progress could be measured with some kind of vocabulary assessment and a spelling test that includes long, affixed words.

For older pupils, we might want to investigate whether teaching Latin and Greek bases assists students trying to comprehend vocabulary in science textbooks (e.g. photosynthesis, hydrology). A reading comprehension task on an appropriate science text could measure progress.

It's debatable whether standardised reading and spelling tests are a useful measure of the effectiveness of morphological interventions because so much is likely to depend on the exact words that occur in the test, and their relationship to the taught material. It’s similar to the difficulties that researchers have when they try to assess the effect of knowledge-rich curricula on comprehension – you’d expect a very gradual build-up of knowledge over time that may not be measurable in a single assessment.

Control groups tasks need careful consideration

We also need to consider what the control groups are doing. The meta-analysis found that there were significant effects of morphological instruction for studies that used ‘business-as-usual’ control groups, but not for those in which the control group did a language-based intervention. Generally, I don’t think morphological interventions are considered to be a replacement for phonics or comprehension interventions, so it may not make sense to compare them. On the other hand, comparing a morphology-intervention group to ‘business-as-usual’ group won’t give us information about what types of language intervention could be most effective.

To complicate things further, the relative effects of different kinds of intervention will depend on the stage of the pupils.

For example, if we compared a morphology intervention with a phonics intervention by testing young children who are still learning basic decoding, we might expect phonics to have a relatively large impact because it targets the decoding skill that the children are rapidly developing.

In contrast, if we compared a morphology intervention to a phonics intervention by testing older pupils who have already mastered most grapheme-phoneme correspondences, phonics would have a relatively small impact on decoding (because pupils are close to ‘ceiling’ level), and morphology would have a relatively large impact – assuming the assessment included challenging, morphologically-complex words.

So, comparisons between different types of intervention really only apply to quite specific contexts.

Where next with ‘morphological instruction’ research?

With all these difficulties coming into play, it’s worth asking whether a meta-analysis on ‘morphological instruction’ can actually give much useful information to educators.

My view is that, rather than thinking about ‘morphological instruction’ as a whole, it’s more useful to think about the effectiveness of specific morphological tools in specific contexts. For example:

Is teaching spelling rules effective at improving spelling of suffixed words for Years 5 and 6?
Are word sums useful tools for analysing word-meaning for 8-yr-olds?
What impact does building morphological matrices have on vocabulary knowledge for Key Stage 4 pupils?
Does the ‘peeling affixes’ strategy help multisyllabic word-reading for teenagers with low reading ages?

Indeed, Colenbrander et al. conclude that “carefully designed studies are needed in order to answer important questions about the key ingredients of morphology instruction, as well as patterns of knowledge transfer and retention.”

What does this mean for educators?

So, does this paper have any implications for how educators should implement morphology instruction? Well, we have evidence that ‘morphology instruction’ works in some cases. However, as there are no clear patterns relating to exactly what works, how much is needed, and who it works for, you’ll have to look at individual studies to figure out whether there’s evidence to support particular strategies that are relevant to your students.

I’d recommend that if you’re trying to teach something and you think that analysing word structure will help to make sense of it, you should try a morphological approach.

For example, if my teenage students want to learn how to spell musician, I can see that a morphological explanation in terms of a word sum (music + ian —> musician) is much more efficient than trying to devise a mnemonic or break it down into individual phonemes or syllables. And there’s the added bonus that if I teach them about the suffix <-ian>, they might be able to apply that to other words.

English is a morphophonemic language, and so if you’re trying help students to understand the writing system, it surely makes sense to teach it as it is! Hopefully further research in this area will provide more information about when and how are the best ways to do that, but in the meantime this paper provides some useful food for thought.

Original paper: Danielle Colenbrander, Alexa von Hagen, Saskia Kohnen, Signy Wegener, Katherine Ko, Elisabeth Beyersmann, Ali Behzadnia, Rauno Parrila and Anne Castles (2024). The effects of morphological instruction on literacy outcomes for children in English‑speaking countries: A systematic review and meta‑analysis. Educational Psychology Review https://doi.org/10.1007/s10648-024-09953-3