Novel findings about syntactic representations

Summary and implications

The format of children’s early syntactic representations constitutes one major controversy in the domain of language acquisition. The Weird Word Order (WWO) paradigm, in which children are presented with scene descriptions using ungrammatical sentences and then are asked to describe new scenes themselves, is just one of many psycholinguistic methodologies to gain insights on children’s syntactic knowledge. And yet, it is particularly interesting since it is part of the controversy, but also brings evidence to resolve it. Results from the WWO paradigm have been exploited to support the constructivist approach suggesting that young children represent word order as a lexical property of each verb they know, developing into abstract syntactic representations only around age 4 (e.g., Tomasello, 2000). However, our review of four studies using this paradigm (Abbot-Smith et al., 2001; Akhtar, 1999; Matthews et al., 2005, 2007) brought evidence for serious problems with the results and their interpretation, questioning the validity of these studies (Franck & Lassotta, 2012; see Section 2.1). Critical inspection revealed methodological issues related to the small number of observations and the discarded data not missing at random, as well as logical/inferential issues concerning the relationship between theory and data that was drawn by the authors. It was argued that the data not only fail to support the constructivist theory, but that it actually supports the alternative theory according to which children represent word order abstractly early on (grammatical approach or parametric approach of grammar; e.g., Hyams, 1986; Wexler, 1998).

The reviewed results of the four WWO studies can be summarized as follows: Young children age 2–3 as well as older children age 4–5 seldom reproduce ungrammatical word orders

and at a similar rate, but young children correct ungrammatical orders less than older children do (effect of age). Both groups of children correct ungrammatical orders more often if they know the verb (effect of lexicality). Both groups of children tend to reproduce the order presented more often if the model is grammatical than if it is ungrammatical; both mismatch ungrammatical orders only – not grammatical orders; both correct ungrammatical sentences into grammatical ones when they mismatch them; both show the hallmarks of productivity in their grammatical sentences (pronominalizations, verbal morphology), but not in their ungrammatical sentences (effect of grammaticality; Franck & Lassotta, 2012). Important logical implications relate to these effects.

First, the sensitivity to grammaticality in younger (as well as older) children can only be taken as evidence for the presence grammar, because grammatical representations of the language’s word order are a necessary condition to account for the observed performances. Second, the sensitivity to lexicality in younger children cannot be taken as evidence for the absence of grammar, because it is also present in older children (and adults; e.g., MacDonald et al., 1994) who are assumed to have a grammar. Third, correcting ungrammatical orders requires more than having a grammar, namely inducing the argument structure from the WWO and inferring that the experimenter’s ungrammatical sentences should be corrected (which the children were not explicitly told to do).

So, fewer corrections in younger children than in older children can be explained by different factors, like insufficient socio-pragmatic skills to infer the experimenter’s expectations.

In our WWO study in French (Franck et al., 2011), children (mean ages 2;11 and 3;11 years) were found to reproduce the ungrammatical word order at a similar, low rate, and to correct it at a similar rate – even with pseudo-verbs. Also, they reproduced the grammatical word order significantly more often than the ungrammatical one and produced grammatical markers in grammatical sentences only. Taking together all five WWO studies, we can confidentially conclude from the data generated with this paradigm that children have a grammar already at age 2, since the presence of grammar is the only possible explanation for the observed effect of grammaticality and a necessary condition of it.

Further arguments for early grammar arise from our intermodal preferential looking experiments on word order representations, suggesting that even before age 2, children represent word order abstractly (Lassotta et al., 2020; see Section 2.2). The comprehension of two grammatical sentence types in French was tested: canonical SVO and non-canonical object-topicalized OSproV structures. Children aged 19–22 months were found to correctly interpret both structures, even though experimental sentences contained pseudo-verbs for which they had no prior lexical knowledge. The combination of these data points with previous observations using the same paradigm (Franck et al., 2013) provides consistent evidence that in

French, young children have abstract knowledge not only of the canonical position of the object, but also of the non-canonical position it occupies in object-topicalized sentences involving movement. The appropriate interpretation of this non-canonical structure is particularly revealing since object topicalization occurs only in about 0.1 % of the clauses of child-directed speech, whereas canonical SVO sentences appear in 41.2 % (Lassotta et al., 2020). With this data at hand, it seems that children do not need a large amount of input of a sentence type before developing the abstract representation of it, as claimed by the constructivist approach. Thus, children appear to dispose of abstract knowledge of head-direction early on, in line with the grammatical approach, and that knowledge of syntactic movement “comes for free” once head-direction is fixed, that is without additional input.

Crucially though, I am not questioning the fact that grammar acquisition is input-driven and the result of a learning process in that certain grammatical properties are learned earlier than others. But it has become evident that at least by the age tested, children have developed abstract, adultlike syntactic representations of word order and movement. So, adaptations to the existing constructivist theory are necessary, since children were found to have a grammar guiding them in comprehension well before age two.

Opening perspectives for future research

The experience I gained over the years in fundamental research in psycholinguistics as well as my intrinsic curiosity and perfectionism gave me enough ideas to write at least two more dissertations. I leave the following proposals arising from the experience of this dissertation work for future research.

Proposal I: Ungrammatical word order study

If I could run another intermodal preferential looking study tomorrow, I would test children’s interpretation of ungrammatical NNV sentences in French (e.g., le garçon la fille dase

‘the boy the girl is pseudo-verbing’). These sentences would be similar to the examined non-canonical OSproV sentences (see Section 2.2), but ungrammatical because lacking the two critical elements of object topicalization: the clitic and the prosodic prominence on the first NP.

During my PhD, I did actually study the interpretation of ungrammatical NNV sentences like le cheval le chien dase (‘the horse the dog is pseudo-verbing’) using the intermodal preferential looking paradigm in 19-month-olds (age range 18–20 months, n = 16), but obtained

only weak results: more looks to the patient-first scene (reflecting an OSV interpretation) than to the agent-first scene (reflecting a SOV interpretation) were found. This effect manifested itself immediately after the first exposure to the test sentence, but not in the following time regions, infants’ looks being dispersed to continuously explore the entire visual scene. So, the effect was short-lived (one 4 s time region) and only marginally significant. Also, ungrammatical sentences were presented intermixed with grammatical NVN sentences and children showed no clear looking preference in these grammatical trials. The finding that children failed to show a systematic preference for the SVO interpretation of NVN sentences was unexpected. How to explain that children showed a preferential interpretation of ungrammatical sentences, but not of grammatical ones? Careful consideration of our auditory materials revealed that in each trial, the pause between the lead-in sentence regarde! ‘watch!’ and the test sentence itself was extremely short, such that the NP following the Verb “watch” could erroneously be parsed as its object (e.g., regarde le cheval le chien dase ‘watch the horse the dog is pseudo-verbing’). In this case, the initial assignment of an object-status to the first NP would further require revision for it to be parsed as the subject of the following verb (of the test sentence). As discussed in Chapter 3, sentence revision requires additional and complex cognitive processes in adults and children alike, which most certainly are too demanding for children aged 19 months. Hence, the lead-in inducing a syntactic garden-path may have prevented infants’ grammatical knowledge to manifest more evidently. Furthermore, ungrammatical sentences preceded 75 % of the grammatical test sentences. Hearing sentences that did not respect the grammar of their language may have confused the children.

My take-home message from this pilot study was how enormously important careful experimental design is, especially with young children. In a follow-up study, but also in general, I would therefore (a) present one sentence type only (or choose a between-subject design) instead of two (in a within-subject design) to avoid any mutual influence, (b) shorten the total duration of the experiment (four items maximum) and reduce the item length (16 s) to lower dropout rates and missing fixations due to fussiness, (c) carefully control pauses and prosody in order to avoid puzzling or null effects as in the pilot study, and (d) last but not least opt for a rate of speech of 3.0 syllables/s, which appears to be the most child-friendly in my experience. By addressing these methodological aspects, I would hope to run the “perfect” experiment and obtain more data points and clearer results.

Moreover, I conducted another pilot study on adults’ interpretation of the ungrammatical NNV structure (e.g., les ours les singes loufent ‘the bears the monkeys are pseudo-verbing’).

Adults (mean age 22 years, n = 18) were presented with written grammatical canonical and

non-canonical sentences as well as ungrammatical NNV and VNN sentences, and asked to identify the agent (e.g., Qui loufe? ‘Who is pseudo-verbing?’) or the patient (e.g., Qui est louvé? ‘Who is being pseudo-verbed?’) of each sentence. As for ungrammatical NNV sentences, the data revealed that adults prefer to interpret the first NP as patient (43 % OSV) over assigning the patient role to the second NP (26 % SOV), none of the NPs (17 % S1S2V), or both NPs (14 % O1O2V). Hence, adults were found to preferably reconstruct the ungrammatical NNV structure as grammatical OSV with object topicalization (e.g., les ours, les singes les loufent ‘the bears, the monkeys are pseudo-verbing them’). Confronting this result with the preliminary finding of children’s OSV looking preference while listening to the same ungrammatical NNV sentences is highly relevant.

It may reveal a continuity in how both adults and children “repair” sentences that do not respect the language’s grammatical word order, suggesting that even young children have similar word order knowledge as adults, and use it to try to make sense out of ungrammatical sentences in a similar way as adults. This child-adult continuity needs to be corroborated by more reliable child data.

Proposal II: Japanese word order study

Another reasonable follow-up of our word order studies in French (see Section 2.2) would be to replicate Omaki and colleagues’ (2012) study investigating Japanese-speaking children’s interpretation of grammatical, canonical NNV sentences, but giving them more possibilities to process these sentences. So far, 19- and 27-month-olds failed to show the appropriate SOV interpretation when being exposed to three presentations of the sentence (Omaki et al., 2012), but 28-month-olds succeeded after six presentations (Matsuo et al., 2012). Before concluding a delay in the comprehension of canonical two-argument sentences in Japanese children as compared to other languages (like French children succeeding at 19 months), I would thus replicate Omaki and colleagues (2012) at age 19 months and 27 months, but give children at least six occasions to parse the sentence (and to establish the link with a corresponding visual scene). Also, I would lower the task demands by testing only NNV sentences (without an additional ungrammatical structure as in Omaki et al., 2012).

A compelling empirical example of how task design influences performance from Qi and colleagues (2020) shows that children’s comprehension performance can be improved by using a slower rate of speech and by presenting fewer experimental conditions (thus providing more time for the one experimental condition tested). In their study, 5-year-olds were able to recover from a

syntactic garden-path previously attested over and over again in the literature (see all the work following Trueswell et al., 1999).

Hence, if Japanese children were able to reach the appropriate SOV interpretation of NNV structures when task demands are lowered, it would strengthen the argument that they dispose of adultlike syntactic knowledge (grammar) but previously failed to show it due to a delay in syntactic processing (use of grammar).

Proposal III: Interrogative word order study

To account for the finding of 22-month-old French-speakers correctly interpreting sentences involving object movement that are extremely rare in the language input (and which use pseudo-verbs), it was argued that once head-direction of the language is set in child grammar, knowledge of movement “comes for free” (see Section 2.2). Given the rather thought-provoking nature of that claim, it is important to determine whether this explanation is extendable to other non-canonical structures like object questions for example. English-speaking 15-month-olds with high productive vocabulary were found to correctly interpret object questions using known verbs (Gagliardi et al., 2016; Perkins & Lidz, 2020). Yet, it is unknown whether they would also succeed with pseudo-verbs, i.e., recognize the empty gap in the object position of unknown verbs.

In ENGLISH. The first step would be to replicate the previous studies with object questions in English with 14–16-month-olds and 19–21-month-olds, but using pseudo-verbs instead of known verbs (e.g., Which boy did the girl gorp?). Finding an interpretative preference with this type of sentences would provide further evidence for children’s use of abstract syntactic knowledge in comprehension.

In FRENCH. The second step would be to test object questions with French-speaking 14–16-month-olds and 19–21-month-olds, again with pseudo-verbs. In French, three question types exist: questions with est-ce que (e.g., Quel garçon est-ce que la fille a pouné? ‘Which boy Q the girl did pseudo-verb?’), questions with inversion (e.g., Quel garçon la fille a-t-elle pouné?

‘Which boy the girl did she pseudo-verb?’), and intonation questions (e.g., Quel garçon la fille a pouné? ‘Which boy the girl did pseudo-verb?’), that is OSV sentences with an interrogative intonation (sentence-final pitch rise). The latter is the most commonly used in colloquial French and child-directed speech (especially with a pronominalized subject).

The idea behind this proposal is that if French-speaking 18–24-month-olds (mean 22 months) correctly interpret OSproV with pseudo-verbs (see Section 2.2), they may also be able

to interpret OSV object questions with pseudo-verbs. Additionally, I would like to explore younger children’s interpretation of these sentences by testing 14–16-month-olds (in comparison to the previous findings in English). Furthermore, I would asses all children’s vocabulary size, which Perkins & Lidz (2020) argued to play a role in comprehension in that the more words the children know/produce, the better they are in using the “gap-driven” interpretation heuristic of recognizing the object gap of known verbs. Given our evidence in favor of abstract word order knowledge (Section 2.2), I expect children in both age groups to show the appropriate preference for the OSV interpretation of NNV object questions (over SOV) despite unavailable lexical verb information. Moreover, I would suggest to reconsider the described interpretation of the link between vocabulary size, i.e., lexical knowledge, and syntactic processing. Actually, vocabulary size/growth appears to be shaped by (language) processing abilities, stronger (language) processing leading to faster vocabulary development (Gathercole, 2006; Stokes & Klee, 2009).

Thus, 15-month-old children with larger vocabularies may succeed better in interpreting object questions than those with smaller vocabularies not because of vocabulary itself, but because they are more efficient language processors. So, an effect of vocabulary size does not necessarily mean that it is lexical (verb-specific) knowledge as such that facilitates comprehension. Rather, it is syntactic processing skills and syntactic knowledge that are primarily required in comprehending object questions. Under the assumption that children dispose of abstract knowledge of word order early on and that the knowledge of syntactic movement “comes for free” once the parameter of head-direction is set, lexical knowledge itself should not play a decisive role in how non-canonical sentences are interpreted. Moreover, the effect of vocabulary size has been found in an experiment using real verbs (Perkins & Lidz, 2020), but not in an experiment using pseudo-verbs (Franck et al., 2013). This leads to think that the effect of vocabulary may be tied to the lexical processing of the (real) verb, rather than to the processing of the syntactical structure. It may be interesting to further explore that hypothesis by systematically comparing children’s performance with verbs and pseudo-verbs to determine whether vocabulary size only plays a role in the former case.

Follow-up studies testing object questions with pseudo-verbs should therefore analyze children’s vocabulary size.

All these proposals demonstrate nicely how syntactic knowledge is intertwined with processing, the topic of the following section, and how tricky but important it is to disentangle both aspects when analyzing comprehension performance.