natural order hypothesis

In his article Krashen’s Monitor and Occam’s Razor Gregg points out some of the problems associated with his natural order hypothesis, as well as his lack of discussion as to why such an order exists. Most of the research this hypothesis is based on are studies of the acquisition of certain morphemes such as the third person, plural, and possessive –s, or the past tense –ed. One problem with these studies which Gregg points out is that these studies are examining formally dissimilar items which may not be comparable. In addition to this criticism the methods used to elicit samples from learners have also been criticized. The method used in most of these studies if I remember correctly is what is called “obligatory occasional analysis”. It is a method of elicitation which requires learners to supply the correct forms in obligatory occasions. One of the problems of this method is that it cannot account for overuse of these morphemes. For example, a learner may produce the correct form on an obligatory occasion but also produce it incorrectly in other occasions. Therefore it is difficult to tell to what degree the learner has actually acquired the morpheme. In addition to this problem these studies have also been criticized on the basis of what has been referred to as the “comparative fallacy”. This is based on the idea that a student’s interlanguage is a distinct from the target language with its own rules and forms. Interpreting the learner’s language in terms of the target norm may actually obscure our understanding of the interlanguage as a distinct system.

Despite these problems with the morpheme studies I became a little interested in the fact that certain morphemes such as the third person –s seem to be acquired rather late despite their frequency in the input. I became more interested in this subject after I read an article last week by Helen Bird et al. (Helen Bird, Mathew A. Lambon Ralph, Mark S Seidenberg, James L McClelland, and Karalyn Patterson, Deficits in Phonology and past-tense morphology: What’s the connection, Jouranal of Memory and Language 48 (2003) 502-56)

This was a study which examined the evidence for what is called a double disassociation between Wernicke’s and Broca’s aphasics in the formation of irregular and irregular past tense verbs. Previous studies had found that Broca’s aphasics are poor at producing regular past tense verbs as in walked and better at producing regular past tense verbs such as bought. Wernicke’s aphasics on the other hand have more difficulty producing past tense irregulars and little difficulty in producing regular forms. This has led some to posit two separate mechanisms for the formation of the past tense, one for regular forms and another for irregular forms. What this study looked at was whether phonological complexity could account for the problems in Broca’s aphasics ability to produce regular forms. By phonological complexity the authors looked at the consonant and vowel structure of the words as well as the consistency of voicing. For example the past tense irregular bought has a CVC structure while moved has a CVCC structure as well as a consistency of voicing on the last two consonants. The authors controlled for these features, phonological complexity and consistency of voicing, and found that the apparent advantage in the production of the irregular past in Brocas aphasics disappeared when these factors were controlled. This lead the authors to argue that there are not two separate systems responsible for forming regular and irregular past tense forms, but one system which draws on phonological and semantic knowledge.

After I read this study I became curious if there was similar work done on the morpheme acquisition in ESL. It would seem reasonable that certain morphemes are more difficult to acquire because of their phonological complexity, such as the –ed forms, or because of the consistency of voicing which make them less salient. For example, when we form a past tense if the final consonant is not voiced the –ed is also not voiced producing two sequential unvoiced consonants as in Walked /walkt/. According to the authors of this study this would make the –ed morpheme less salient phonologically.

I have not had time to do a thorough search of the literature, but I did find one study which examined this question among others. It was a study done by Goldschneider and Dekeyser: (Jennifer M. Goldschneider, Robert M. DeKeyser (2005) Explaining the “Natural Order of L2 Morpheme Acquisition” in English: A Meta-analysis of Multiple Determinants, Language Learning 55, 27-77)

This study examined whether five factors, perceptual saliency, semantic complexity, morphophonemic regularity, syntactic category, and frequency, could account for the order of acquisition of several morphemes. Their results indicated that the combination of these properties could explain to a large extent the acquisition order of the morphemes they included in their study. They suggest that these factors be grouped into a broader conceptualization of “salience” along with L1 transfer (which they did not include in their study) may account for most of the varience in the order of acquisition of the morphemes.

I don’t have a lot of time to go into detail of how they define each of the five factors which make up “salience”, and there may be some limitations with this type of study. They use what they call a meta-analysis which pools data from several other studies. I have a limited knowledge of research methods, so I don’t know how valid this type of research is. I did think it was an interesting study and wanted to share it with anyone who might be interested.