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Early child L acquisition: Age or input effects? Neither,
or both?*
SHARON
UNSWORTH
Radboud University, Nijmegen
(Received December –Revised October –Accepted December –
First published online February )
ABSTRACT
This paper explores whether there is evidence for age and/or input
effects in child L acquisition across three different linguistic
domains, namely morphosyntax, vocabulary, and syntax–semantics.
More specifically, it compares data from English-speaking children
whose age of onset to L Dutch was between one and three years
with data from children whose age of onset was between four and
seven years in their acquisition of verb morphology, verb placement,
vocabulary, and direct object scrambling. The main findings were that
there were no significant differences between the two groups in any of
these areas and, with the exception of scrambling, current amount of
exposure was the only factor significantly related to children’s scores.
The paper discusses the theoretical significance of these findings with
respect to the role of input in the language acquisition process and the
claim that there is a critical period ending within (early) childhood.
INTRODUCTION
One of the most robust findings in second language (L) acquisition research
is that there are age effects, that is, in the long term, L children typically
outperform L adults, though whether these age effects take the form of a
critical period remains controversial (see Muñoz & Singleton, , for a
recent review). Generally, age effect studies in L acquisition compare L
children with L adults, most usually when the children are already adults
at testing. Whilst in this context various ages within childhood have been
proposed as the age at which the ability to acquire an L to nativelike
[*] Earlier versions of this paper were presented at EUROSLA at York University, at
BUCLD , and at Mannheim University. I would like to thank audiences at all three
for their useful comments, and in particular Holger Hopp and Jason Rothman. Thanks
to two anonymous reviewers and the editors for their constructive feedback. Finally,
thanks to all participating children, families, and schools, as well as the research
assistants involved in data collection. Address for correspondence: Radboud University
Nijmegen, Postbus Nijmegen HD, Netherlands. e-mail: s.unsworth@let.ru.nl
J. Child Lang. (), –. © Cambridge University Press
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levels starts to decline (e.g. age – years; Johnson & Newport, ), until
recently there has been little systematic investigation of the potential role of
age of onset WITHIN childhood and its impact upon child L development.
Within this limited body of research, a number of studies have suggested
that for certain aspects of morphosyntax, age effects may be observed at a
(much) earlier age than proposed in previous literature. More specifically,
it has been claimed that children whose age of onset is around age four or
later acquire their L in a similar fashion to L adults and, crucially, in a
fundamentally different way from the children whose age of onset is before
this age (Kroffke & Rothweiler, ; Meisel, , ; Rothweiler,
; Sopata, ). For example, in his study on the acquisition of
subject–verb agreement and clitic placement in first language (L) German
children acquiring French as L, Meisel () found that children whose
age of onset was between three and four made errors typical of L adults,
such as using subject-clitics with non-finite verbs. These findings are
argued to be consistent with the notion of a critical (or sensitive) period
for (certain aspects of) morphosyntax, ending around age four, after which
nativelike acquisition (gradually) becomes impossible (see Meisel, ).
Similarly, Kroffke and Rothweiler () and Rothweiler () examined
the acquisition of word order, subject–verb agreement, and subordinate
clauses in L Turkish children acquiring German as L. These authors
observed that the children whose age of onset was between three and
four patterned similarly to monolingual L children in terms of the
developmental errors which they (did or did not) make, whereas those
whose age of onset was older showed developmental patterns reminiscent
of L adults. In short, then, whilst there is some variation in terms of the
exact age of onset of the children involved, there are a number of studies
on different L/L combinations suggesting that there are age effects for
certain aspects of morphosyntax in early childhood.
Whilst the longitudinal data analyzed in these studies provide a crucial
insight into the developmental trajectories of their participants as they
unfold, many of these studies involved a limited number of children only
and they neglected to (systematically) take into account other factors known
to vary with age of onset. As noted by Flege (), age of onset is a
macro-variable which correlates with other factors including L proficiency,
language dominance, frequency of (L/L) use, and kind of input (native vs.
non-native). For claims about the existence of a critical period, age, that is,
biological maturity, IS the crucial factor, however. This means that any
assessment of the role of age of onset in early childhood should control for
possible effects of these other factors before drawing conclusions about the
possibility of a critical period. In this paper, we will attempt to do this by
including estimations of input quantity (at the time of testing and over time)
in our analyses of children’s developing L.
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There is a considerable body of literature demonstrating the impact of
differential amounts of input on bilingual/L children’s rate of acquisition
(see Unsworth, in press, for a recent review). Variation in input quantity
has been shown to be related to, amongst other things, vocabulary (e.g.
Pearson, Fernández, Lewedeg & Oller, ; Thordardottir, ), verbal
morphology (Nicoladis, Palmer & Marentette, ; Paradis, ),
nominal morphology (Thomas, Williams, Jones, Davies & Binks,
), and grammatical gender (Gathercole & Thomas, ; Unsworth,
), as well as to more comprehensive assessments of children’s
grammatical abilities (Chondrogianni & Marinis, ; Hoff, Core, Place,
Rumiche, Senor & Parra, ).
The number of studies examining input effects ACROSS a range of linguistic
domains within the same group of children is limited, however, and
furthermore, the results of these studies are mixed. Thus, whilst several
studies have found comparable relationships between input and rate of
acquisition across domains, others have not. For example, in their study
on English/Spanish bilingual toddlers, Hoff et al. () observed similar
patterns in the relationship between rate of acquisition and both
vocabulary and grammar scores (on the CDI). Likewise, Paradis ()
observed that the same input factors, namely length of L English
exposure and richness of the English environment, emerged as significant
predictors of children’s scores on vocabulary and verbal morphology (see
also Bohman, Bedore, Pena, Mendez-Perez & Gillam, ). These results
contrast with those of Chondrogianni and Marinis (), who found that
acquisition of vocabulary and complex syntax (i.e. passives, wh-questions)
were affected by input factors, whereas the acquisition of verbal
morphology was not. Likewise, Unsworth () also found differences
across domains: in her study of English/Dutch bilingual children aged
four through seventeen, she observed that whereas amount of input was
related to children’s scores on grammatical gender, no such relation was
observed with their acquisition of direct object scrambling, a property of
Dutch involving the syntax–semantics interface.
Unsworth () argued that because the information needed to acquire
the meaning restrictions on scrambling is simply unavailable in the input
(a ‘poverty of the stimulus’ problem), differences between bilingual
children in terms of amount of exposure should be largely irrelevant, and
hence no input effects are expected. She claimed that to fully understand
the role of (variation in) input on children’s developing language abilities,
it is important to consider not only where input effects are expected but
also where they are not, or at least where the role of input should be more
minimal.
To date, there are only a handful of studies examining both the role of
input and the role of age at the same time. In a cross-linguistic
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comparison of the acquisition of grammatical gender by English/Dutch and
English/Greek children with varying ages of onset, Unsworth, Argyri,
Cornips, Hulk, Sorace, and Tsimpli () found that amount of input
was a significant predictor of children’s accuracy scores in both Dutch and
Greek, but age of onset was not. There were, however, some age-related
differences in the Greek data: children with age of onset at birth were
significantly more accurate on masculine and feminine nouns than children
first exposed to Greek at age two or later. The authors related these
cross-linguistic differences to the timing of acquisition in monolingual L
development (see also Tsimpli, ), which in turn they linked to the
comparative opacity of the Dutch gender system when compared with the
Greek (following Gathercole & Thomas, ). Similarly, in a
longitudinal study of the acquisition of French by Swedish-speaking
children, Ågren, Granfeldt, and Thomas () also observed input
(quantity/quality) effects on later acquired target language properties
(subject–verb agreement), whereas earlier acquired properties (finite/
non-finite verb forms) were more strongly related to age of onset than
input. In short, there is reason to believe that age and input effects may
interact with each other and therefore one should not be considered
without the other.
Another factor which correlates with age of onset, again reflecting its status
as a macro-variable (Flege, ), is L proficiency. There is by now a
considerable body of research demonstrating L transfer effects in child
L acquisition, especially but not exclusively in the domain of
morphosyntax (e.g. Blom & Baayen, ; Chondrogianni, ;
Unsworth, ; Zdorenko & Paradis, ). Furthermore, under
certain – as yet not completely understood – conditions, cross-linguistic
influence is also attested in simultaneous bilingual language acquisition
(see Serratrice, , for review).
The goal of this paper is to draw together these various lines of research to
test for both age effects and input effects in a range of linguistic domains in
child L acquisition of Dutch, namely morphosyntax, lexicon, and syntax–
semantics. The specific properties tested are verb morphology and
placement, receptive vocabulary, and direct object scrambling. We now
briefly review previous research concerning possible age and input effects
for the bilingual/child L acquisition of these particular properties in
order to formulate some concrete predictions. Age effects in the present
context are understood as differences between L children whose age of
onset is before age four and L children whose age of onset is at age four
or older. Input effects are understood as a significant relationship between
variation in amount of exposure and L children’s (developing) language
abilities.
EARLY CHILD L ACQUISITION: AGE AND/OR INPUT EFFECTS?
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AGE AND INPUT EFFECTS ACROSS DOMAINS
We start with the domain of morphosyntax. Verbal inflection in
Dutch is relatively impoverished. The present tense paradigm, illustrated
in (), consists of three forms: –ø, –t, and –en. There is a distinct
infinitive form, marked by the suffix –en, and this is homophonous with
PL finite forms. The focus of the present study is on the SG and PL
contexts only.
() Singular Plural
SG drink – ø drink – en
SG drink – t drink – en
SG drink – t drink – en
Dutch is a verb-second (V) language, which means that in declarative main
sentences the finite verb always appears in second constituent position with
any non-finite verbs in sentence-final position, as in (a) (Koster, ).
When some element other than the subject appears in sentence-initial
position, for example, an adverbial (b) or a topicalized object (c),
subject–verb inversion takes place.
() a. Ik heb gisteren een appel gegeten
I have yesterday an apple eaten
‘I ate an apple yesterday.’
b. Gisteren heb ik een appel gegeten
yesterday have I an apple eaten
‘Yesterday I ate an apple.’
c. Een appel heb ik gisteren gegeten
an apple have I yesterday eaten
‘An apple, I ate yesterday.’
A number of studies have examined age effects in the child L acquisition of
verb morphology and placement in Dutch and German (also a V language).
The findings are mixed. Kroffke and Rothweiler () and Sopata ()
observed that children with an age of onset (AO) of around four made the
same errors as L adults, that is they produced non-finite forms in finite (V)
position, whereas children with an earlier age of onset did not, that is they
patterned like monolingual L children (see also Tran, ). These results
contrast with Blom (), who found that L children with AO of four were
highly accurate and did not produce non-finite –en forms in V position.
Sopata () also observed that the three L Polish children in her study
acquiring LGerman systematically produced utterances with the finite verb
in third rather than second position (V), illustrated in (), whereas there was
little evidence for such L transfer in Blom’s () study of L Turkish and
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Moroccan Arabic / Tarafit-speaking children (consistent with Meisel, ;
but cf. Haznedar, ).
() *Gisteren ik heb een appel gegeten
yesterday I have an apple eaten
‘Yesterday I ate an apple.’
In line with most (though not all) of the aforementioned studies, the
prediction for the acquisition of verb morphology/placement is that there
will be age effects, that is, we expect L children with age of onset at four
or older to produce non-finite forms in finite positions and to produce V
utterances, whereas children whose age of onset was before age four will
do neither.
With respect to input effects, as noted above, various studies have
observed bilingual/L children’s rate of acquisition of verb morphology to
be related to differences in amount of input (Blom, ). To the best of
my knowledge, this relationship has yet to be addressed for the acquisition of
V, at least for bilingual/L children. Given that the evidence available in the
input to the language-learning child that Dutch is a V language is rather
limited, it is expected that input effects will be found for this property, too.
The rationale for this prediction is as follows. In an analysis of parental
input to the monolingual Dutch-speaking child Hein in the CHILDES
corpus, Yang (, p. ) observed that whilst subject-initial main clause
utterances such as (a) predominated, appearing at a rate of %, XVSO
utterances as in (b) and OVS utterances as in (c), where the finite verb
is clearly in second position, were much more infrequent (% and %,
respectively). For Yang, the crucial data were in fact the OVS utterances
only, as on his parameter-setting approach this is the only word order to
unambiguously distinguish Dutch as a V language from other languages,
such as Hebrew. Yang proposed that because OVS utterances were so
infrequent in the input, L Dutch-speaking children would need
some time to arrive at the correct parameter setting of V, and
he presented a reanalysis of the monolingual Dutch-speaking child
Hein’s data in support of his claim. The crucial observation for present
purposes is that non-subject-initial utterances, that is, the evidence to the
language-learning child that Dutch is a V language, constitute a relatively
small part of the input. Extending Yang’s observations to acquisitional
settings where the input is significantly reduced, such as child L
acquisition, one would expect this effect to (potentially) be more severe. In
other words, input effects are also expected in the child L acquisition of
V in Dutch.
The predictions for the acquisition of vocabulary are straightforward.
Given that vocabulary acquisition continues into adulthood, there is in
principle no reason to believe that there should be age effects in this
EARLY CHILD L ACQUISITION: AGE AND/OR INPUT EFFECTS?
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domain. As noted above, input effects are widely attested in the acquisition
of vocabulary by bilingual/L children (e.g. Thordardottir, ). Hence,
the prediction for the present study is that we should find input but no
age effects in the domain of vocabulary.
Finally, we turn to the acquisition of syntax–semantics, an area which has
received little attention in the bilingual/child L acquisition literature (but
see Sorace & Serratrice, ). The property of Dutch to be investigated is
direct object scrambling, and more particularly, the interpretive constraints
on scrambled indefinite objects. In English, indefinite objects in negative
sentences such as () are ambiguous and can thus be interpreted either
specifically or non-specifically, that is, the sentence in () can be
paraphrased as ‘The boy didn’t catch any fish’ (non-specific interpretation)
or ‘There’s a fish the boy didn’t catch’ (specific interpretation).
() The boy didn’t catch a fish
In Dutch, these two interpretations are associated with different word orders,
that is, indefinite objects in the scrambled position, as in (b), are interpreted
specifically, whereas those which remain in their non-scrambled, or ‘base’
position within the verb phrase (VP), receive a non-specific interpretation,
as in (a); it is generally assumed that scrambling is the result of syntactic
movement to some higher (VP-adjoined) position (de Hoop, ), which
position exactly is not important for the present discussion.
() a. De jongen heeft geen (niet + een) vis gevangen (not > a)
the boy has no not a fish caught
‘The boy didn’t catch a(ny) fish.’
b. De jongen heeft [een vis]i niet ti gevangen (a > not)
the boy has a fish not caught
‘There’s a fish that the boy didn’t catch.’
It is important to note that, in addition to indefinites, other types of objects
(e.g. definite objects and pronouns) may also scramble, albeit without
the same truth-conditional implications, and that scrambling occurs in
conjunction with other (scope-taking) sentence adverbials besides negation,
such as ‘twice’, and in these cases, no suppletive forms (such as geen in (a))
are involved. Furthermore, scrambling of indefinites is highly infrequent,
occurring in just % (/) of cases (van Bergen & de Swart, ).
Research has shown that L adults are able to acquire interpretive
constraints on scrambling and comparable properties in other languages
(Hopp, ; Marsden, ; Unsworth, ), and on the basis of this
Golberg, Paradis, and Crago () have shown that an older age of onset may in fact confer
an advantage when it comes to rate of acquisition of vocabulary, but we will not consider
this interpretation of age effects here.
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and other literature, it has been argued that there is no critical period for
(compositional) semantics (Slabakova, ). The prediction for the
present study is therefore that there will be no age effects within childhood
for scrambling.
The predictions concerning input effects are as follows. If the acquisition
of the interpretive constraints on scrambled indefinites constitutes a ‘poverty
of the stimulus’ problem (Unsworth, , ), no input effects are
expected. The argument for the poverty of the stimulus for this particular
property of Dutch is laid out in Table , following the five criteria given
by Pullum and Scholz (). Whilst these conditions are not entirely
unproblematic (see for example Schwartz & Sprouse, for a critique),
they are included here as they provide a systematic way to qualify the
acquisition of certain linguistic properties as a poverty of the stimulus
problem (but see Rothman & Iverson, ).
To sum up, if the information required to acquire the property in question
is underdetermined by the input, then it should in principle not matter
if the amount of input to which a child is exposed is reduced or varies.
Table presents a schematic overview of the predictions tested in the
current study.
TABLE . How the acquisition of the interpretive constraints on scrambled
indefinite objects in Dutch constitutes a poverty of the stimulus problem
(following Pullum and Scholz’ () specification schema)
. ACQUIRENDUM
CHARACTERIZATION
Describe what is to be acquired
Scrambled indefinite objects restricted
to specific interpretation.
. LACUNA SPECIFICATION
Identify set of sentences learner would need
to access to acquire () on basis of input alone
Sentences containing scrambled
indefinites in contexts where (i)
availability of specific interpretation is
apparent, and (ii) unavailability of
non-specific interpretation is, too.
. INDISPENSABILITY ARGUMENT
Explain why () cannot be acquired without
()
Indefinite objects are almost always
non-specific, and non-scrambled.
. INACCESSIBILITY EVIDENCE
Show that () is not available to learner
Scrambled indefinites are incredibly
rare. Other objects scramble more
frequently but no such
truth-conditional differences between
scrambled and non-scrambled orders
(van Bergen & de Swart, ).
. ACQUISITON EVIDENCE
Show that () is indeed acquired
L children restrict scrambled
indefinites to specific interpretation by
age six, as do (many) simultaneous
bilingual children (Unsworth, ;
Unsworth et al., ).
EARLY CHILD L ACQUISITION: AGE AND/OR INPUT EFFECTS?
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METHOD
Participants
The participants in this study (n= ) were children who had English as
their first language (L) and were learning Dutch as their second language
(L). English was the only (or main) language spoken at home and
children had been exposed to this language from birth. All children were
resident in the Netherlands at the time of testing, and twenty-two were
born there. Exposure to Dutch was either from daycare or school,
depending on the child’s age, out-of-school activities, and/or the local
environment. Children were divided into two age of onset (AO) groups,
namely those whose age of onset was no earlier than one year and before age
four years, and those whose age of onset was at age four but before age eight
(Schwartz, ; Unsworth, ). Details of the participants’ background
and experiential variables are given in Table . Traditional length of exposure
was calculated in the usual fashion, i.e. by subtracting children’s age of onset
from their age at time of testing; CUMULATIVE length of exposure is a measure
of exposure of time taking into account differences in amount of exposure of
the years (see Unsworth, , for more details).
Given the differences in age of onset, there are also inevitable differences
in age at testing (see Muñoz, , for relevant discussion). In general,
children in both groups have comparatively more day-to-day exposure to
English than to Dutch. In the AO< group, three children attended
Dutch-language daycare, twenty-four attended schools where Dutch was
TABLE . Predictions for age and input effects across domains
Domain Property Age effects? Input effects?
Morphosyntax Verb morphology Yes Yes
Verb placement
Lexicon Vocabulary No Yes
Syntax–semantics Scrambling No No
TABLE . Mean values (and standard deviations) for background and
experiential variables
Variable
Children with
AO< (n= )
Children with
AO5 (n= )
Age of onset ; (;) ; (;)
Age at time of testing ; (;) ; (;)
Current % exposure % () % ()
Traditional length of exposure (in years) ; (;) ; (;)
Cumulative length of exposure (in years) ; (;) ; (;)
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the main or only language of instruction, and the remaining seventeen
children in this group attended schools where English was the main or
only language of instruction. In the AO5 group, thirteen children
attended schools were Dutch was the main or only language of instruction
and the remainder attended (predominantly) English-language schools
with separate language classes in Dutch.
Tasks and procedure
Verb morphology and placement was tested using two elicited production
tasks. The first task was designed to elicit data for both verb form and
verb placement (Blom, Polišenskà & Weerman, /; Polišenskà, ).
Children were shown a picture of two people carrying out the same
activity but with different objects, e.g. a man painting a door and a man
painting a chair. The verb was introduced in the prompt in the infinitival
form (Kijk! Deze twee plaatjes gaan over verven ‘Look! These two pictures
are about painting’), and the child was asked to tell the experimenter what
was happening. For example, the experimenter started the sentence for the
child with the subject (Deze man . . . En die man . . . ‘This man . . . And
that man . . .’) and the child was expected to complete it (. . .verft een deur
‘is painting a door’ . . . verft een stoel ‘is painting a chair’). In total there
were twenty-four items, all targeting the present simple tense, distributed
evenly across SG (n = ) and PL (n = ) forms and three different
word orders, namely subject-initial main clauses, non-subject-initial main
clauses, and embedded clauses (n = for each). The example given
above illustrates the subject-initial main clause condition. In the
non-subject-initial main clause, the prompt included an adverbial, Op dit
plaatje . . . En op dat plaatje . . . ‘On this picture . . . And on that picture
. . .’, designed to force subject–verb inversion, i.e. verft de man een stoel.
All the verbs were bisyllabic and had a stem ending on a sonorant or
fricative; each verb was elicited four times, twice with a singular subject
and twice with a plural subject. The selected verbs were aaien ‘stroke’,
dromen ‘dream’, gooien ‘throw’, spelen ‘play’, dragen ‘carry’, geven ‘give’,
kussen ‘kiss’, lezen ‘read’, verven ‘paint’, and wassen ‘wash’. Items targeting
grammatical gender were included as fillers (Unsworth, ).
In the embedded clause condition, a boy looking through binoculars was introduced and the
prompt included a main clause and complementizer which the child was expected to
complete with an embedded clause, e.g., De man ziet dat . . . ‘The man sees that . . .’
followed by de man de stoel verft. In contrast to main clauses, the finite verb in embedded
clauses appears in clause-final position. Children’s acquisition of this particular property
of Dutch will not be discussed in any detail in this paper.
Blom, Vasic, and de Jong () have shown that monolingual children are more likely to
omit verbal inflection with stems ending on a plosive and hence these were avoided in the
present study.
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For the assessment of children’s verb morphology, children’s responses
were scored as percentage correct, that is, the number of target forms
(main verb + –t in SG condition or main verb + –en in PL condition)
divided by the number of scorable responses (main verb + –t, main verb
+ –en, and bare verbs). Reponses involving, for example, the past tense,
the present continuous construction is/zijn aan het + infinitive, or the
auxiliary gaat + infinitive were excluded from analysis.
For the assessment of children’s verb placement, and more specifically
their knowledge of V, only responses in the non-subject-initial main
clause condition were considered. Children’s responses were scored as
percentage correct, that is the number of responses with target word order
(V) divided by the number of scorable responses (V +V). Responses
where the subject was missing or where an auxiliary form was used instead
of the main verb were excluded from analysis.
In the second elicited production task, children’s knowledge of V was
examined in a sentential context where a topicalized object appeared in
sentence-initial position (cf. (c)). This task was included because Tran
() found higher accuracy rates for production of V when the
constituent in first position was a topicalized object rather than a
PP-adverbial, as is the case in the previous task. In this task, children were
presented with a series of objects on cards and were asked questions about
them by a puppet, Worp, who was introduced to the children as coming
from outer space. The child’s task was to help the puppet understand
‘how things work on planet earth’. The child was first shown a picture and
the puppet asked Wat is dat? ‘What is that?’ Once the child answered with
the target object name, the puppet would repeat the name of the object as
though she was hearing it for the first time and then she would ask a
second question, namely X? Wat kun je met X doen? ‘X? What can you do
with X?’, where X was the name of the object. The experimenter
subsequently started the child’s response with the object, i.e. Vertel ‘t even
aan Worp. Aardbeien . . . ‘You tell Worp. Strawberries . . .’ using a rising
intonation, and the child was expected to complete e.g. . . . eet je ‘lit: eat
you’ or kun je eten ‘lit: can you eat’). There were no restrictions on the
verb which the children were allowed to use in their responses.
As an anonymous reviewer points out, in elicitation tasks such as these children’s responses
may be categorized as incorrect not because they do not have the targeted knowledge but
because they have failed to pick up on the experimenter’s prompt, which in both tasks is
crucial in order to create the required syntactic context for V. Whilst we cannot of
course rule out that children chose to ignore the prompt provided, every endeavour was
made during testing to ensure that they did pay attention to it, for example in the
instructions in the beginning (“I start (the sentence), and you finish it off”), and
throughout testing if children for example started to respond without waiting for the
experimenter to speak (“No, please wait. First I start, and then you finish.”).
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There were seven target items using the following objects: boeken ‘books’,
een konijn ‘a rabbit’, een gitaar ‘a guitar’, melk ‘milk’, kleren ‘clothes’,
appelsap ‘apple juice’, and een krant (a newspaper). Six filler items
showed pictures of different kinds of people and the child was expected to
tell the puppet what each person did (e.g. Een tandarts . . . ‘A dentist’ . . .).
The fillers were excluded from the present analysis. Children’s responses
were scored as percentage correct, that is, the number of responses with
target word order (V) divided by the number of scorable responses (V +
V). As in the first elicitation task, responses where the subject was
missing were excluded from analysis. The data from this second task were
not analyzed for verb morphology because in the context of subject–verb
inversion used here, the –t suffix is dropped in a SG context.
Vocabulary was assessed using the Dutch version of the Peabody Picture
Vocabulary Task, PPVT-III-NL (Dunn, Dunn & Schlichting, ). In
this task, children are shown four pictures and asked to select the one
which best represents a single word pronounced by the experimenter. The
procedures given in the testing manual were followed. Standard scores (for
monolinguals) are reported.
Scrambling was tested using a using a truth-value judgement task. In this
task, based on Krämer () and adapted further by Unsworth, Gualmini,
and Helder (), children were presented with a story in which the main
character manipulated two out of a set of three objects; for instance, a boy
caught two out of three available fish in a pond. In other words, the
scenario presented to the children was consistent with a specific
interpretation of the relevant indefinite object (e.g. there was a fish that
the boy did not catch) and inconsistent with a non-specific interpretation
(i.e. it is not the case that the boy caught a fish). Subsequently, a puppet
was asked to describe what had happened in the story and, in doing so,
uttered a negative sentence containing a scrambled indefinite (cf. (b)).
The child’s task was to judge the truthfulness of this statement. On the
target – specific – interpretation, the expected answer is ‘yes’, whereas on
the non-target – non-specific – interpretation, the expected answer is ‘no’.
Fillers (n = ) were used to ensure that children could cope with true
negatives, irrespective of their knowledge of scrambling. Accuracy scores
were calculated for each child by dividing the number of target responses
by the total number of items (n= ).
The target objects were chosen on the basis of extensive piloting as those most likely to be
known to children and those most likely to elicit a usable utterance. During the pilots we
tried to restrict the verbs children produced to main verbs only but this proved to be
impossible. For this reason, both auxiliary and main verbs are included in the analysis of
this task. Unfortunately, this does mean that the data from the two elicitation tasks are
not entirely comparable.
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Children were tested in each language in a separate session by a (near-)
native-speaker research assistant. The sessions took place either at daycare/
school or at the child’s home, depending on their age and the parents’
wishes. All three tasks were part of a larger test battery and were always
conducted in the following order: vocabulary, verb morphology/placement
tasks in the order presented above, scrambling. For all tasks except
vocabulary, the order of presentation of the test items was counterbalanced
across children. Test sessions were videotaped and responses on the verb
morphology/placement were later checked by a second experimenter. A
randomly selected subset (approximately %) were crosschecked by a
second tester to calculate inter-rater reliability; the Kappa statistic was
very high (·, p < ·) indicating almost perfect agreement (Landis &
Koch, ).
RESULTS
For verb morphology and placement, children who consistently failed to
include a subject or who consistently used alternatives were excluded (for
verb form, this was children in the AO< group and children in the
AO5 , and for verb placement, and children, respectively, in the
first task (ADV in initial position), and and children, respectively, in
the second task (OBJ in initial position)). Alternative responses used an
auxiliary or the present continuous construction aan het + infinitive. It is
important to note that while such responses are uninformative for the
present purposes, they are perfectly acceptable in the context, and they are
also regularly produced by monolingual L children (Polišenskà, );
furthermore, despite not providing a response suitable for analysis in the
present study, these responses also show that the children clearly
understood the task.
In the scrambling task, children who demonstrated a response bias or who
failed on more than fillers, thereby showing a lack of understanding of true
negatives, were excluded from the analysis ( children in the AO< group
and children in the AO5 ). Finally, for the vocabulary task, three
children in the AO< group were unable to complete the task following
the standard procedure and hence had to be excluded from analysis. The
results for all five outcomes are presented in Table .
An ANCOVA was carried out for each outcome variable separately with
group (AO< vs. AO5 ) as between-subjects factor and age at testing,
(cumulative) length of exposure, and current amount of exposure as
covariates. A main effect of group was interpreted as evidence for age
effects, and when either of the two experiential variables was found to be
a significant covariate, this was interpreted as evidence for input effects.
The results for verb morphology and verb placement are presented in
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Figures and ; note that the plotted values are estimated marginal means
and therefore differ from the values in Table . The estimated marginal
means for vocabulary are (SE ) for the AO< group and (SE )
for the AO5 group; for scrambling, these are % (SE %) for the AO
< group and % (SE %) for the AO5 group.
There was no main effect of group for verb morphology (cf. Figure ),
either for SG (F(,) = ·, p= ·) or PL (F(,) = ·, p = ·), for
verb placement (cf. Figure ), either for ADV (F(,) = ·, p = ·) or
OBJ (F(,) = ·, p= ·), for vocabulary (F(,) = ·, p = ·), or
TABLE . Mean scores (and standard deviations) for verb morphology (%
correct for SG, PL), verb placement (% correct for V), vocabulary
(standard score), and scrambling (% scrambled indefinites interpreted
specifically)
Outcome Children with AO< Children with AO5
Verb morphology – SGa % (%) % (%)
Verb morphology – PLa
% (%) % (%)
Verb placement –ADVb
% (%) % (%)
Verb placement –OBJb % (%) % (%)
Vocabularyc () ()
Scramblingd % (%) % (%)
NOTES: a number of main verbs with target morphology divided by number of scorable
responses; b number of responses with target V order divided by number of scorable (V
+V) responses; c standard score; d number of scrambled indefinite objects interpreted
specifically divided by total number of items.
Fig. . Verb morphology (SG and PL): percent correctly inflected verbs (estimated
marginal means and standard error).
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for scrambling (F(,) = ·, p= ·). The covariate age at testing was not
significantly related to children’s scores on SG (F(,) = ·, p = ·),
PL (F(,) = ·, p = ·), verb placement with ADV (F(,) = ·,
p = ·) or OBJ (F(,) = ·, p = ·), vocabulary (F(,) = ·,
p = ·), or scrambling (F(,) = ·, p= ·). This was also the case for
the covariate (cumulative) length of exposure: SG (F(,) = ·,
p = ·), PL (F(,) = ·, p= ·), verb placement ADV (F(,) =
·, p = ·), verb placement OBJ (F(,) = ·, p = ·), vocabulary
(F(,) = ·, p = ·), or scrambling (F(,) = ·, p = ·).
The covariate current amount of exposure was, however, significantly
related to children’s scores on SG (F(,) = ·, p< ·, ηp= ·), PL
(F(,) = ·, p= ·, ηp= ·), verb placement ADV(F(,) = ·,
p < ·, ηp = ·), verb placement OBJ (F(,) = ·, p= ·, ηp= ·),
and vocabulary (F(,) = ·, p = ·, ηp= ·), but not to their scores
on scrambling (F(,) = ·, p = ·).
The analysis for verb form and verb placement has concentrated on –
respectively – proportion of verbs with the correct form irrespective of
position, and proportion of verbs in the correct position irrespective of
form. For a complete understanding of children’s knowledge of verb
morphology and placement, it is, however, crucial to also examine these
two variables in tandem to determine whether finite forms appear in finite
positions only. For this analysis, SG only responses are used as the
correct form of the plural verb is homophonous with the infinitive (e.g. ze
verven ‘they paint’ and verven ‘to paint’), which means that correctly
inflected (finite) forms of the verb are indistinguishable from incorrect
Fig. . Verb placement (with adverb (ADV) or topicalized object (OBJ) in initial position):
percent verbs in V position (estimated marginal means and standard error).
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(non-finite) forms. Children’s responses in the SG/V condition were
classified as belonging to one of the following four categories: non-finite
form in V position (a), non-finite form in V position (b), finite form
in V position (cf. ()), and finally, the only correct response, namely
finite form in V position (cf. (b)).
() a. *Op dit plaatje de man verven een deur
on this picture the man paint a door
b. *Op dit plaatje verven de man een deur
on this picture paint the man a door
The results are presented as raw figures in Table and as proportions in
Figure .
When childrenmade errors, thesewere errors of placement only, orplacement
and form, that is, when children failed to produce a target finite form in V
position, they produced either a finite or a non-finite form in V position.
TABLE . Contingency table for verb form and placement (number of responses)
Children with
AO<
Children with
AO5
V V V V
Form Finite
Non-finite
NOTES: AO= age of onset; V= finite verb in second constituent position; V= finite verb in
third constituent position.
Fig. . Verb form and placement: error types. Proportion of responses within group of
given type.
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There were no children (in either group) who produced non-finite forms in V
position. An analysis of the individual children’s results reveal that the
non-finite forms in V position are produced by six (out of thirty-five)
children with AO < (two with one token, one with two tokens, one with
three tokens, and two with four tokens) and twelve (out of thirty-five)
children with AO ≥ (four with two tokens, four with three tokens, and four
with four tokens). Finite forms in V position were produced by twelve
children with AO < (four with one token, six with two tokens, one with
three tokens, and one with four tokens) and by fifteen children with AO ≥
(four with one token, seven with two tokens, and four with four tokens).
DISCUSSION
In this paper, we presented data from English-speaking children acquiring
Dutch as an L in order to investigate the role of age of onset and input
quantity in (early) child L acquisition. Children were divided into two
age groups, those whose age of onset was between the ages of one and
three years and those whose age of onset was between the ages of four and
seven years. Three different linguistic domains were targeted: children’s
knowledge of verb morphology and verb placement (morphosyntax) was
examined using two elicited production tasks, vocabulary was tested using
the standardized, receptive PPVT task (in Dutch), and the interpretation
of scrambled indefinite objects (syntax–semantics) was accessed using a
truth-value judgement task.
Our first prediction was that, for verb morphology and placement, there
would be age effects and input effects. The results indicated no significant
differences between the two groups on either verb morphology or
placement, irrespective of the type of constituent in initial position (ADV
or OBJ). In other words, once age at testing, (cumulative) length of
exposure, and current amount of exposure were controlled for, the
children whose AO was four years or older did not produce significantly
more errors than children whose AO was younger than four years, despite
having had less exposure to Dutch overall. Moreover, children in both
groups produced similar types of errors, namely finite and non-finite
forms in V position. The covariate current amount of exposure was
significantly related to children’s accuracy scores and explained % of the
variance in the data for SG, % of the variance for PL, % of the
variance for verb placement with an adverbial in initial position, and %
of the variance for verb placement with an object in initial position. In
short, then, our prediction concerning input effects in the domain of
morphosyntax was borne out, whereas our prediction for age effects was not.
The production of V is often classified as an error which is typical for L
adults and, as such, in previous work has been used to argue that L children
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(AO5 ) pattern like L adults rather than L children (Sopata, ).
Given that children in the younger AO group also made these types of
errors, albeit to a lesser degree, the same line of argumentation cannot be
used here. If it were, then one would have to claim that the relevant age at
which a purported critical period should end is earlier than around age four.
There are two possible (and not mutually exclusive) explanations for
children’s production of V utterances. The first is that, in the first
elicitation task, participants produced more V utterances than they may
otherwise have done as a result of the probe employed in the task. Recall
that in this task the children were presented with two pictures of people
carrying out the same activity but with different objects; in the
non-subject-initial main clause condition the experimenter started
the utterance for the child with the adverbial Op dit plaatje . . . Op dat
plaatje . . . ‘On this picture . . . On that picture . . .’. We cannot rule out the
possibility that the children failed to pick up on this cue and simply
proceeded with what for them was a subject-initial main clause. This does,
however, seem unlikely: data from monolingual four- to seven-year-old
children (n = ) using the same task contained just three such tokens, i.e.
finite forms in V position, produced by two different children. If the L
children produced more V utterances as the result of a methodological
artefact, one would expect the monolingual children to do this, too, but
they did not.
Rather than a methodological artefact, it is the bilingual/L children’s
other language, English, which may be the source of their non-target V
responses, at least in the first elicitation task. This would be in line with
several studies showing robust transfer effects in child L acquisition of
word order (e.g. Mobaraki, Vainikka & Young-Scholten, ; Unsworth,
). It is also possible that these errors may be due to limited
proficiency in or exposure to Dutch. At this stage, there is no way to tease
apart these two possibilities.
On the whole, children were more targetlike in their production of V on
the task where the finite verb was preceded by an object in sentence-initial
position than on the task where the finite verb was preceded by a
PP-adverbial. This is in line with Tran (), who also found that L
English children acquiring German were more accurate in the production
of V in contexts with a topicalized object than in contexts with a
preposed PP-adverbial. There are (at least) two possible explanations for
the observed difference in children’s production of V in these two
different contexts. The first is that this may simply be due to the type of
data elicited: main verbs in SG and PL contexts in the ADV task versus
main and auxiliary/modal verbs in SG contexts in the OBJ task. For
example, it may be easier to produce the verb in the correct place in a
context where inflection has to be dropped, as is the case for verbs with a
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postverbal SG subject in the OBJ task, rather than in a context where
inflection is obligatory, as is the case for SG. The second is that it is also
possible that the lower scores in the adverbial-initial context reflect an
increased likelihood of transfer from English in this context. It would
seem that English PP-adverbials, such as On Monday, are more likely to
appear in sentence-initial position than topicalized objects, and this in turn
may mean that crosslinguistic influence is more likely in a comparable
context in Dutch.
A final noteworthy observation concerning verb form and placement is the
fact that none of the children, in either group, used non-finite forms in V.
This is in line with L children with L Turkish and Moroccan Arabic /
Berber in Blom (), but contrasts with other studies such as Tran
() and Rothweiler (). In this sense, the L children in the present
study pattern more like L children in their acquisition of verb
morphology, but they are more like L adults in their verb placement in
that they use V word order, as Sopata () also found for the L
German children in her study.
The predictions for vocabulary were that children’s scores were not
expected to differ across AO groups but they were expected to be related
to the input variables. Both these predictions were borne out. Once age at
testing, (cumulative) length of exposure, and current amount of exposure
were controlled for, there was no significant difference between the AO<
and the AO5 groups in their scores on the standardized vocabulary
task. Current amount of exposure was, however, significantly related to
their scores and explained % of the variance. The observation that
amount of input is a significant predictor of children’s vocabulary scores is
in line with previous literature on bilingual/L children (e.g. Hoff et al.,
; Pearson et al., ; Thordardottir, ).
It is noteworthy that while there is quite some variation in children’s
scores, scores for both groups are quite high: both groups have a standard
score of on average , which means that they fall within age-appropriate
monolingual norms. This is all the more surprising given that children in
both groups have rather limited exposure to Dutch, namely on average
% in the AO< group and % in the AO5 group. Taken together
with the comparatively small effect size (ηp= ·), these results suggest that
other factors are likely to be at play in these data. One such factor may be
the typological similarity between English and Dutch, which means that
children may have been able to make use of cognates to arrive at the target
response on the vocabulary task. Whilst a detailed analysis of the cognate
vs. non-cognate items goes beyond the scope of this paper, studies on
The children in Sopata’s () study produced non-finite forms in V, though, which both
monolingual children and the children in the present study do not do.
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other bilingual/L populations suggest that the availability of cognates may
indeed impact upon children’s vocabulary scores and should be taken into
account when comparing results across studies (e.g. Dijkstra, ;
Stadthagen-González, Gathercole, Pérez-Tattam & Yavas, ).
We now turn to the domain of syntax–semantics. No age effects were
predicted and this prediction was borne out. The finding that the children
with AO5 performed similarly to children with AO< is in line
with Slabakova (), who argues that there is no critical period for
(compositional) semantics, as well as with a large body of literature
demonstrating that L adults are able to acquire targetlike knowledge of a
range of linguistic phenomena at the syntax–semantics interface.
With respect to input, it was argued that the acquisition of the interpretive
constraints on scrambled indefinite objects constitutes a poverty of the
stimulus problem (Unsworth, ), and consequently no input effects
were predicted. In line with this prediction, children’s scores on the
truth-value judgement task were neither related to current amount of
exposure nor to cumulative length of exposure. In fact, children in both
groups scored almost at ceiling, indicating target knowledge of this
particular property of Dutch, despite their rather limited exposure to Dutch.
There is, however, a potentially complicating factor in this analysis,
namely the (unpredicted) possibility of transfer from English in this
particular experimental context. Whilst indefinite objects in negative
sentences (cf. ()) are in principle ambiguous, when we examined data
from a task in English comparable to the one reported on here for Dutch
(based on Miller & Schmitt, ), we found that most children showed a
preference for the specific interpretation. We therefore cannot rule out the
possibility that when children allowed the specific interpretation in Dutch,
they did so because they transferred their preferred interpretation from
English, rather than because they were employing targetlike knowledge of
Dutch.
There is nevertheless reason to believe that L transfer cannot be the
whole story. When we compare children’s response patterns on the Dutch
and English tasks, we find evidence to suggest that they DO differentiate
their interpretations across the two languages. Whilst the vast majority of
children (/) (almost) always accepted the specific reading in both
languages, almost all of the children (/) who had a different response
pattern in their two languages allowed an interpretation in English
(non-specific) which they did not appear to allow in Dutch, or which they
at least allowed less frequently. In a study with a larger group of
simultaneous bilingual children (Unsworth, ), similar tendencies were
observed. Thus, whilst the results concerning children’s knowledge of
scrambling are less clear-cut than they appeared at first blush, the fact that
children differentiated their responses in English and Dutch in this way
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suggests that when they accepted the target-specific interpretation in Dutch,
they did not necessarily do so as a result of L transfer. In other words, they
appear to have overcome the poverty of the stimulus (see Unsworth, ,
for an account of how they exactly they might do this). A summary of the
findings across all three domains for both age and input is provided in
Table .
Comparing results across different domains, the present study provides
little evidence for age effects in (early) child L acquisition, including in
domains where they have been observed in previous studies, for example
for verbal morphology/placement. One reason for this might be that, in
contrast to most of the earlier studies (e.g. Rothweiler, ), this study
also takes into account factors which co-vary with age of onset, such as
input quantity. It is, however, important to bear in mind that failing to
find a significant difference between groups does not mean that we can say
that there is evidence AGAINST age of onset effects; there may be a
multitude of reasons for why such a difference was not found. All we can
say at this stage is that for the target language properties and two groups
of children here, no significant differences were observed. It is worth
noting, however, that similar findings obtain when the dividing line
between the two groups is drawn at age three or at age six (Meisel, ;
Sopata, ), and when the age of onset is included as a continuous
variable in a regression analysis, that is, there remain no significant
differences between the two groups and age of onset is not a significant
predictor. An alternative approach, which may more readily detect age of
onset effects, should they exist, might be to compare more differentiated
groups, for example a group of children whose age of onset is between two
and three years with a group of children whose age of onset is between six
and seven years. Unfortunately, there are not enough children in the
present dataset to carry out such an analysis.
In the present study, children’s scores for verb morphology, verb
placement, and vocabulary were significantly related to their current
amount of exposure. This finding underscores the importance of treating
TABLE . Findings for age and input effects across domains
Domain Property Age effects? Input effects?
Morphosyntax Verb morphology No Yes
Verb placement
Lexicon Vocabulary No Yes
Syntax–semantics Scrambling No No
I thank Jesse Snedeker for drawing this possibility to my attention.
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age of onset as a macro-variable (Flege, ,) and including variation in, for
example, input quantity and quality in any analysis of age effects in (early)
childhood. Given that input quantity and quality (in part inevitably) vary
between children who start acquiring their L earlier and children with an
older age of onset, it is essential to control for these variables before
concluding that age is the crucial factor. Similarly, for a complete picture
of input (or age) effects in early child L/bilingual acquisition, it is
necessary to examine linguistic domains where such effects are expected,
and crucially where they are not. Whilst further research is necessary to
(dis)confirm the pattern of findings observed here, the present study
illustrates the need to go beyond target language properties such as verb
morphology and vocabulary and examine more complex syntactic
phenomena, and/or phenomena which involve interaction between
different domains.
Finally, let us consider the theoretical implications of the present study’s
findings. In several studies examining the relationship between variation in
input and bilingual children’s language outcomes, the existence of input
effects has been argued to support a usage-based (or constructivist)
approach to language acquisition (e.g. Gathercole, ; Hammer,
Komaroff, Rodriguez, Lopez, Scarpino & Goldstein, ; Hoff et al.,
; Paradis, Nicoladis, Crago & Genesee, ). Indeed, the findings for
verb morphology, verb placement, and vocabulary in this study are
consistent with such an approach. Oversimplifying somewhat, the general
idea is that if language is acquired in a piecemeal fashion on the basis of
the input, we can expect an effect of relative amount of input for bilingual
children across different domains, and crucially in the acquisition of
grammar/morphosyntax as well as in the acquisition of vocabulary.
Whilst the logic of this argument is undisputed, it is worth noting that, as
yet, the focus of much of the research in this area has been on linguistic
properties such as verbal morphology and vocabulary, that is, properties
where input effects would be expected on any approach to (bilingual/
second) language acquisition. Expanding the domain of enquiry to
(complex) properties where input severely underdetermines the knowledge
children acquire, as well as explaining why input effects are not always
found is an important – and arguably, crucial – step in implementing this
approach to the language development of bilingual/L children (see e.g.
Goldberg, Casenhiser & Sethuraman, , for one proposal concerning
monolingual children and O’Grady, , on L acquisition).
The present study’s finding that, despite the relative infrequency of
indefinite objects in scrambled position, (at least some) L children come
to know that these are restricted to a specific interpretation, is arguably
hard to reconcile with a usage-based approach to bilingual acquisition,
such as for example that of Gathercole (). It is, however, in principle
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consistent with the nativist approach, where this acquisitional task
constitutes a ‘poverty of the stimulus’ problem (Unsworth, ). The
observation that there are input effects for verb morphology and placement
are also consistent with this approach (see Yang, , on V, for
example). However, to more thoroughly test differences between these two
approaches, much more specific predictions are required, especially from a
nativist perspective, where variation in input and its impact on the
developmental process has only recently started to be taken (more)
seriously (see, e.g. Miller & Schmitt, ; Omaki & Lidz, in press; Yang,
; cf. Blom, Paradis & Sorenson Duncan, , for a recent
demonstration of to the child L acquisition of verb morphology within a
usage-based approach).
There are a number of limitations to the present study. First, it included a
range of linguistic domains, but the number and type of phenomena
investigated nevertheless were quite limited. For example, vocabulary was
examined using a receptive one-word standardized task only. Furthermore,
the tasks used for each of the three target phenomena were different
(elicited production, receptive standardised task, truth-value judgement);
for completely comparable data, similar methodologies should be
employed in future studies. The analysis of input effects was limited to
input quantity only; it is likely that differences in input quality will also
impact on children’s L development (Unsworth, in press). Finally, as
discussed in detail above, the interpretation of the scrambling data were
complicated by the possible role of L transfer. Once again, additional
research is needed to address this issue.
CONCLUSION
The present findings suggest that input (quantity) is an important factor in
(early) child L acquisition, and in the context of the English/Dutch
children studied here, it appears to be more important than age of onset.
Nevertheless, input effects were not observed across the board, and where
they were observed they were not equally large. Across domains,
crosslinguistic influence (or transfer) from the children’s other language,
English, contributed to the some of the observed response patterns,
As pointed out by an anonymous reviewer, the different domains are not all investigated
using the same modality in the present study: lexical (vocabulary) and syntactic–semantic
(scrambling) knowledge were assessed using receptive skills and morphosyntactic
knowledge (verb form and placement) using productive tasks. Assuming that both
receptive and productive skills reflect the deployment of underlying linguistic knowledge,
and that this is what is affected by the factors tested here, namely age of onset and input
quantity, it seems unlikely that differences in task modality can account for the study’s
findings (see Paradis, , for relevant discussion). However, we cannot rule out that
other tasks may lead to different results.
UNSWORTH
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https://doi.org/10.1017/S030500091500080X
sometimes in non-negligible ways. Taken together, these findings reiterate
the need for a more multi-faceted approach to age effects in child L
acquisition, whereby the influence of factors known to covary with age of
onset is ruled out before concluding that biological maturity is a (or even
THE) key determinant of children’s second language acquisition.
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UNSWORTH
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The Robustness of Critical Period Effects in Second Language
Acquisition (2000)
Robert M. DeKeyser (University of Pittsburgh, USA)
Studies in Second Language Acquisition, 22(4), pp.499-533
One of the two hypotheses tested in DeKeyser’s study is the Critical
Period hypothesis, which states that an individual beyond a particular
age lacks the language learning skills a child has (DeKeyser, 2000, p.500).
A topic of controversy within the field of linguistics, the Critical Period
was conceived by Penfield and Roberts (1959) and later Lenneberg
(1967). As there are critical periods in an individuals’ life for brain
development, their concept states that there is a particular age range
during which a language should be learnt in order to reach a native-like
standard. The language learning ability of an individual gradually
declines between after puberty, usually around the ages of 16 or 17
(Johnson and Newport, 1989).
A second hypothesis DeKeyser investigated in his study was the
Fundamental Difference hypothesis. Popularised after its
formulation by Bley-Vroman (1988), this hypothesis details that an
adult is incapable of depending upon the innate mechanisms for
language acquisition available to them as a child. Children can learn
their native language without ease, though this is not the case for most
adults. An adult therefore must form alternative problem-solving
mechanisms in order to successfully acquire an additional language
(DeKeyser, 2000, p.500-501).
1) Theoretical Foundation
The results from the study confirmed a strong negative
correlation between the age of acquisition of English and the
score on the grammaticality judgement test. The tests also
showed that aptitude plays a pivotal role in an adult language
learner, as analytical and problem-solving skills are key to successfully
acquire an additional language successfully. As predicted, varying
structures showed differing degrees of correlation with age of
arrival.
There are four principal conclusions which can be drawn from
DeKeyser (2000).
1) Learners with high verbal ability are exempt from the
critical period effect as they have the ability to use explicit learning
mechanisms in order to successfully acquire an additional language.
2) The fundamental difference hypothesis is confirmed as no
adult reached a native level without relying upon such explicit language
learning mechanisms
3) Aptitude is a predictor of ultimate attainment in L2 and the
age an individual arrives in the US determines their verbal ability
4) There is a critical period – at some point during childhood or
puberty, all people lose the mental capacity required in order to achieve a
native standard in an additional language.
5) Results and Conclusion
Carroll, J. B., & Sapon, S., 1959. Modern Language Aptitude Test: Form
A. New York: The Psychological Corporation.
Bley-Vroman, R., 1988. The fundamental character of foreign
language learning. In W. Rutherford & M. Sharwood Smith (Eds.),
Grammar and second language teaching: A book of readings (pp. 19– 30). Rowley,
MA: Newbury House.
Johnson, J. and Newport, E., 1989. Critical period effects in second
language learning: The influence of maturational state on the
acquisition of English as a second language. Cognitive Psychology, 21(1),
pp.60-99.
Lenneberg, E., 1967. Biological foundations of language. New York: Wiley.
Ottó, I. (1996). Hungarian language aptitude test: Words in sentences.
Unpublished manuscript, Department of English Applied Linguistics,
Eötvös Loránd University, Budapest.
Penfield, W. and Roberts, L., 1959. Speech and Brain Mechanisms.
Princeton, New Jersey: Princeton University Press.
Transparent. 2021. Take Hungarian Language Quizzes. [online] Available
at:
6) Bibliography
The main purpose of DeKeyser’s study researching the Fundamental
Difference hypothesis and the robustness of the Critical Period
is to replicate the results of a study conducted by Johnson and Newport
(1989). Their investigation proved the Fundamental Difference
hypothesis correct, affirming the fact that the Critical Period does exist.
In addition to this, DeKeyser recognised that not a single empirical study
has been conducted which tests the Fundamental Difference hypothesis
to test its various features (DeKeyser, 2000, p.500). The findings obtained
from his study would therefore be instrumental to the second language
acquisition research field. Through taking methodological criticisms into
account highlighted in the subsequent years after Johnson and Newport’s
study (1989),
De Keyser formed the following three hypotheses to investigate
(DeKeyser, 2000, p.507-508).
1) Participants in this study will show a strong negative correlation
between age of arrival and performance on a grammaticality
judgement test, but with some overlap in range between child and
adult acquirers
2) Those adult acquirers who score within the range of child
acquirers will all have high verbal aptitude, which may have
allowed them, at least in part, to learn the L2 grammar through explicit
reflection on rules
3) Different elements of grammar will show different
correlations with age of acquisition; not all structures are equally
sensitive to the critical period effect
2) Rationale and Research Hypotheses
The participants in DeKeyser’s study were 57 native speakers of
Hungarian (32 male and 25 female) from a 200-mile radius
surrounding Pittsburgh, Pennsylvania. In order to obtain results from an
unbiased and varied sample, the participants came from a wide range
of ages and varying socioeconomic status levels. As an additional
requirement for the study, the participants had to be living in the
United States for at least ten years without having been significantly
exposed to English until their migration to an English-speaking country.
3) Participants
DeKeyser employed three research instruments in order to test his
hypotheses. Each participant was met with either individually in their
own home or in a room on the University of Pittsburgh campus
(DeKeyser, 2000, p.510).
The first part of the study was a Background Questionnaire. It was
two pages long and consisted of general questions about individual
variables such as their language and educational background, their age
of arrival in North America and age at time of test (DeKeyser, 2000,
p.510).
The second part of the study was the Grammaticality Judgement
Test. Through using the framework from Johnson and Newport’s study
(1989), the individual listened to 200 items which had been tape-
recorded by a male native speaker of English. Each item had been
paired with another, and the participant was required to identify odd and
irregular pairs (DeKeyser, 2000, p.509-510). The test took around 55
minutes to complete.
The final part of the investigative procedure was the Language
Learning Aptitude Test, modelled by that of Carroll and Sapon
(1959) and amended into Hungarian by Ottó (1996). Over
approximately a 20-minute period, participants were required to read
stimulus sentences from a sheet and elect the correct answers from a
multiple-choice selection. The test consisted of 20 five-way multiple
choice items.
4) Methodology
Student ID: XXXXX
Grammaticality Judgement Test Example
A snake bit she on the leg.*
Susan is making some cookies for us.
The baby bird was has fall from the oak tree. *
The little boy was counting all his pennies last night.
(DeKeyser, 2000, p.527)
Language Learning Aptitude Test Example
Inkább egy kétágyas [room] szeretnék fürdőszobával
a) Szobát b) kettő c) szálloda
Megvan a [my ticket] a 492-es járatra?
a) Elvámolnivalóim b) helyfoglalásom c) jegyem
(Transparent, 2021)
