Only the present pro-
gressive auxiliary, which had a higher value for semantic com-
plexity, emerged in an unpredictable order within the last part
of the hypothesized sequence. Through the removal of outliers,
accuracy of the predicted sequence of morphological acquisi-
tion was increased to rs = 0.694 (p = 0.083).
Although individual causes such as frequency, sonority, com-
plexity, morphological alternations, and syntactic complexity
partially explain morphosyntactic development, their integra-
tion serves as a stronger predictor of the acquisition process.
Higher correlations between the predicted order of acquisition
and the Processability Model and Natural Order suggest that
multiple causal factors are concomitantly responsible for the se-
quences observed in historical studies. Because each causal
factor may be partly responsible for the acquisition process, an
approach to explicit instruction should utilize input and peda-
gogical techniques commensurate with causal characteristics of
each target feature.
Since morphosyntactic development can be predicted through
the synthesis of multiple causes, grammatical sequences such as
those found in the Processability Model and Natural Order
should no longer be explained away as the manifestation of an
innate, mysterious force. Results of this study reveal that the
acquisition process has concrete causes which can be both un-
derstood and modified to enhance instruction. The educator
may now work to engineer explicit grammar instruction that
hastens acquisition or promotes uniform development of mor-
phosyntactic features. Given the method of calculation within
this paper, however, features having outlying causal values can
skew the significance of other more minute disparities between
features. Syntactic (e.g., question inversion) and lexical features
(e.g., past regular), for example, have large numbers of alterna-
tions and high sonority values, which skew key differences
between less variable and less sonorant morphological features.
To increase the accuracy of predictions, syntactic and lexical
features should be separated from morphological features for
In order to apply predictions of acquisition to practice, the
educator must develop a scale that describes appropriate in-
structional interventions for each grammatical feature. To illus-
trate how this may be accomplished, a 4-point scale was devel-
oped for the 16 morphosyntactic features analyzed within this
study. Values for each causal variable were divided into quar-
ters and assigned a scale value (0% - 25% = 4; 26% - 50% = 3;
51% - 75% = 2; 76% - 100% = 1). Ratings of 1, which are as-
signed to higher causal values that may hasten the acquisition
process, require little emphasis; ratings of 4, in contrast, are
assigned to lower causal values that may slow the acquisition
process, suggesting they require more extensive curricular em-
phasis. Due to the aforementioned influences of syntactic and
lexical outliers, ratings for syntactic/lexical and morphological
features were calculated separately. After grammatical features
were converted into the 4-point scale, causal variables of fre-
quency, alternations, semantic complexity, morphosyntactic
complexity, and sonority were paired with the corresponding
instructional interventions respectively: input, pronunciation,
visual images, grammar exercises, and listening exercises. The
results were then compiled into Table 5.
The values in Table 5 yield several insights as to how ex-
Copyright © 2012 SciRes. 119
plicit grammar instruction should be modified to hasten acqui-
sition of selected features. First, highly sonorant features that
have a listening rating of 1, such as progressive -ing, should not
receive extensive emphasis within listening input. Those having
a listening rating of 2, in contrast, such as the progressive aux-
iliary or copula, should appear twice as often in listening dia-
logues. Features with ratings of 3 and 4 require even more em-
phasis. They should appear in listening dialogues three to four
times more often than those with a rating of 1. According to
Table 5, grammatical features with the lowest sonority, such as
the past tenses, third person singular -s, possessive -s, plural -s,
do questions, and yes/no questions, require the highest degree
of emphasis within listening and verbal input to ensure acquisi-
Second, complex syntactic features such as cancel inversion,
question inversion, and separable phrasal verbs, which have
high ratings of 3 to 4 in the grammar exercise category, should
be more highly emphasized through strategies such as focus-
on-form and written exercises that draw attention to the rela-
tionships between grammatical elements of a sentence. Com-
plex morphemes (third person singular -s, possessive -s, plural
-s, past regular, and progressive -ing) should also be substan-
tially emphasized through exercises that highlight their gram-
matical function. Overall, morphosyntactic features with ratings
of 2, 3 or 4 should respectively have 2, 3 or 4 times more
grammar exercises than those which have a rating of 1.
Third, features with high semantic complexity, such as the
article, auxiliary questions, and cancel inversion, should be ac-
companied by the largest amounts of visual stimuli (e.g., pic-
tures, videos, graphic organizers), thereby facilitating under-
standing of semantic relationships and sociolinguistic contexts.
Video conversations in a supermarket, for example, could be
used to show contexts in which the definite article is used (e.g.,
“Is this the new product you’ve been talking about?”).
Fourth, features with a large number of alternations, such as
questions, articles, the progressive auxiliary and copula, should
be emphasized highly within explicit grammar curricula. De-
liberate attempts should be made to infuse alternative forms
into aural and written input. As with the categories for listening,
grammar exercises, and visuals, features with larger pronuncia-
tion ratings should have a commensurate expansion of content.
Finally, features with the lowest frequency, such as cancel
inversion, the progressive auxiliary, and the possessive -s, should
be emphasized most extensively. Due to their rating, these fea-
tures should appear approximately four times more often than
those with a rating of 1. If normal, rather than accelerated, ac-
quisition of features is desired, frequencies commensurate with
those found in native contexts can also be infused within the
As can be seen from the above recommendations, designing
grammar instruction using a scale such as that featured in Table
5 is needed. Unlike other methods of curriculum design, which
create uniform tasks for each grammatical feature via a one-
size-fits-all paradigm, this new approach tailors the curriculum
to each grammatical feature in a way that maximizes the acqui-
sition process. Although Table 5 provides useful information
for curriculum designers, it still has one major limitation. It is
designed with the assumption that all causal variables equally
influence the acquisition process. Results in this study suggest
that factors such as sonority and frequency may have a larger
influence on morphological features than other causal factors
(See Table 3). This assertion is confirmed when only values of
sonority and frequency are integrated and correlated for mor-
phological features; the resulting correlation is the best predic-
tor of the Natural Order, yielding a value that is highly signifi-
cant (rs = 0.849; p = 0.016).
While isolating the significance of causal factors is straight-
forward in some circumstances, similar correlations of causal
factors to some morphosyntactic features complicate assessments
of individual influences. Values for morphosyntactic alterna-
tions, sonority, and morphosyntactic complexity, for example,
will become larger as syntactic features grow in size. This may
explain why integrating semantic complexity, sonority, morpho-
syntactic alternations, and frequency, without the most signifi-
cant causal factor of morphosyntactic complexity, also yields
the same highly significant correlation to the Processability
Model (rs = 0.821; p = 0.007) obtained in Table 4.
Table 5.
Guide for curriculum design.
(Semantic Complexity)
Grammar Exercises
(Syntactic Complexity) Listening (Sonority)
1. Progressive -ing 2 1 2 3 1
2. Progressive Auxiliary 4 4 3 2 2
3. Copula 2 4 2 2 2
4. Past Regular 3 3 2 3 4
5. Third Person Singular -s 2 3 2 4 3
6. Plural -s 1 3 2 3 3
7. Possessive-s 4 3 2 3 3
8. Article 1 4 4 1 2
9. Negation 2 1 2 1 1
10. Past Irregular 1 3 2 1 4
11. Separable Phrasal Verb 2 2 2 3 2
12. Do-Questions 3 1 2 3 3
13. Wh-Copula Questions 2 3 3 3 2
14. Yes/No Questions 1 2 4 3 3
15. Wh-Auxiliary Questions 3 4 4 3 1
16. Cancel Inversion 4 4 4 4 1
1 = low emphasis needed 2 = medium emphasis
3 = medium high
emphasis needed 4 = high emphasis needed
Copyright © 2012 SciRes.
Historical studies of morphosyntactic acquisition order could
not be pragmatically applied to education, since causes and as-
sociated effects on the acquisition process were not well known.
Although more recent research has worked to identify how
multiple causes interact to affect acquisition order, the small
scope of this research has limited its utility. Results of the cur-
rent study suggest that extending the scope of study by predict-
ing the order of a larger number of morphosyntactic features
can lead to a better understanding of the L2 acquisition process.
This understanding, in turn, may be used to modify both ESL
and EFL input in ways that promote the uniform acquisition of
multiple morphosyntactic features.
Although this study provides useful information for curricu-
lum designers, more study is needed to increase the effective-
ness of explicit grammar curricula. First, more morphosyntactic
features must be studied and combined into a comprehensive
scale. Second, the disparities of predictive validity for each
morphosyntactic feature must be further examined and refined.
Finally, the degree to which each individual causal factor in-
fluences the acquisition process must be more concretely de-
termined. Through examination of each limitation, educators
can accurately predict how reforms will impact second lan-
guage learners, thereby allowing explicit grammar curricula to
be engineered that are highly effective. Methodological reform
of curricula is particularly necessary in EFL contexts, where
limited resources and input have been shown to negatively
impact the acquisition process (Chen, 2007; Lee, 2005; Liao &
Fukuya, 2004).
I would like to express my special appreciation to Professor
Wonkyung Choi for serving as a corresponding author on this
project. I would also like to thank my wife Jinny, son Matt, and
daughter Katie for their patience and understanding, without
which I could not have completed this paper.
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Appendix A
Table A1.
Grammar features, corpus search strings, and frequencies.
Plural (-s, -es)
*s.[n] POS List noun.PL 7,459,308
Singular Copula ( is, ‘s)
is -[v] 2,382,962
's.[v] -[v] 1,298,254
Progressive (- ing)
[v?g*](includes non prog elements) 4, 237, 206
Progressive Auxiliary (is, ‘s)
is (collocate) *ing.[v] 417, 714
's.[v] *ing.[v] 341, 157
Past Regular
*ed.[v?d*] POS List verb.ED 2, 575, 784
Past Irregular
-*ed.[v?d*] POS List verb.ED 10, 740, 546
Possessive ('s)
[n] 's 677,015
Third Per son Singular -s
[v?z*] 10, 371, 795
subtract -is 3, 987, 516
subtract –’s 2, 016, 509
subtract -has 1, 130, 455
subtract -does 347, 046
Total: 2, 890, 269
Article (a, an, the)
a|an|the 35, 098, 329
Particle Verbs
[v*] [n*] [in|into|at|on|up|down|off|under|out|over|back|around|about 19,
[v*] [n*] over|through|with|without|away|across|for|to|after|for 73,
Total: 92, 316
Negation + Verb
Not 1, 784, 767
No 833, 269
TOTAL: 2, 618, 036
.|;|:|,|" do [pp*]|[n*] 69, 779
Yes/No Inversion
.|;|:|,|" do|does|did|will|would|can|could|should|have|had|has|must|might
[pp*]|[n*] 165, 855
Wh-Copula Inversion
1. what|when|how|why|where|who|whom|whose [vb*] [pp*]|[n*] 79, 511
2. how long|many|much [vb*] [pp*]|[n*] 1, 215
TOTAL: 80, 726
Wh-Auxiliary Inversion
1. what|when|how|why|where|who|whom|whose
[pp*]|[n*] [v*] 33, 889
2. how long|many|much
[pp*]|[n*] [v*] 3, 606
3. what|when|how|why|where|who|whom|whose [vb*] [pp*]|[n*] *ing.[v]
10, 145
4. how long|many|much [vb*] [pp*]|[n*] *ing.[v] 419
TOTAL: 48, 059
Wh Do-fronting
1. what|when|how|why|where|who|whom|whose do [pp*]|[n*] [v*] 57, 259
2. how long|many|much do [pp*]|[n*] [v*] 1, 371
TOTAL: 58, 630
Cancel Inversion 1.
if|what|when|how|why|where|who|whom|whose [n] * [v*] 3, 971
how long|many|much [n] * [v*] 1, 411
TOTAL: 5, 382
Appendix B
Table B1.
Categories of wh-aux question types.
(Master, 1996: p. 141)
(Master, 1996: p. 12)
Subject Pronouns
(Master, 1996: p. 149)
What Do I
When Does You
Where Did He
Who Will She
Whom Would It
Whose Can They
Why Could We
How Should
How long Have
How many Had
How much Has
Is (Progressive)
Am (Progressive)
Are (Progressive)
Was (Progressive)
Were (Progressive)
Table B2.
Sonority scale.
Sound Point Value Examples
Low Vowels 12 a, æ
Mid Vowels 11 e, o
High Vowels 10 i, u
Glides 9 w, y
Flaps 8 r
Laterals 7 l
Nasals 6 m, n, ŋ
Voiced Fricative 5 v, z, ð
Voiceless Fricative 4 f, s, θ, h, ʃ
Affricate 3 t
̬ʃ, dʒ
Voiced Stop 2 b, d, g
Voiceless Stop 1 p, t, k
Appendix C
Table C1.
Semantic complexity calculation (Adapted from Brown, 1973).
Morpheme Meanings
1. Progressive -ing
2. Plural
3. Past Irregular
4. Past Regular
5. Possessive
6. Present Copula
7. Article
8. Third Person Singular -s
9. Present Progressive Auxil-
10. Negation (No/Not)
11. Do-fronting
12. Phrasal Verb
13. Wh Copula Question
14. Yes/No Question
15. Wh Auxiliary Question
16. Cancel Inversion
Temporary duration
Specific-nonspecific; com-
mon/proper nouns; mass/count
nouns; generic statements
Temporary duration; number
Earlierness; number; future; tempo-
rary duration
Question; earlierness; number;
Question; earlierness; number;
future; Temporary duration
Question; earlierness; number;
future; Temporary duration
Question; earlierness; number;
future; Temporary duration
Copyright © 2012 SciRes. 123
Copyright © 2012 SciRes.
Table C2.
Complexity for morphological and syntactic features.
Syntactic Categories Points
Free 1
Bound 2
Free 3
Bound 4
Inter-phrasal 5
Inter-sentential 6
Appendix D
Table D1.
Predicted sequence of acquisition for all features.
Morphosyntactic Feature Z Score Value
1. Past irregular 0.82
2. Article 0.68
3. Negation 0.31
4. Is Copula Combined 0.19
5. ING 0.17
6. Plural -s 0.16
7. Past regular 0.03
8. Do questions 0.02
9. Is Prog Combined 0.01
10. Poss s 0.01
11. Third person singular –0.10
12. Wh Copula –0.14
13. Phrasal verb separated –0.25
14. Yes/no aux questions –0.39
15. Wh aux questions –0.69
16. Cancel Inversion –0.86
Appendix E
Table E1.
Morphological features (Syntactic, lexical, and frequency outliers re-
Morphosyntactic Feature Z Score Value
1. Negation 0.83
2. Progressive -ING 0.75
3. Plural -s 0.28
4. Is Copula 0.05
5. Past Regular –0.31
6. Possessive -s –0.35
7. Third Person Singular –0.48
8. Is Progressive –0.78
Table E2.
Correlations to the natural order (syntactic, lexical, and frequency out-
liers removed).
Predicted Sequence of Acquisition
r 0.694
p 0.083
Natural Order
N 7