A standard observation in linguistics is that an expression of a given syntactic, semantic or phonological category may become part of another expression if both hold the same category. This computation, named recursion, that is implemented by tucking a constituent into another, is widely recognized as a fundamental cognitive capacity. An interesting discussion in this field tries to define the domain specificity of recursion, that is, if it lies in the underpinnings of language capacity (CHOMSKY, 2005; FITCH; HAUSER; CHOMSKY, 2005; HAUSER; CHOMSKY; FITCH, 2002) or if is an integral part of general cognitive resources and is called into action as an external factor (ARSENIJEVIC, HINZEN, 2010; ARSENIJEVIC, HINZEN, 2012). While the first option would explain the fact that recursion is supposed to be a major language principle found in all languages (cf. localized dispute in EVERETT, 2005, 2007; NEVINS, PESETSKY, RODRIGUES, 2009), the second option makes it easier to understand the multiple characteristics that involve the implementation of recursion in different aspects and phrases of different languages.
A significant factor that can shed light onto this discussion is the acquisition of recursion. How and when exactly do children start processing recursion? On one hand it does not seem to be present in children’s earliest utterances (ROEPER; SNYDER, 2004, 2005; ROEPER, 2011). Contrastingly, coordination appears as an earlier acquisition in language comprehension and production (PÉREZ- LEROUX et al., 2012).
The fact that coordination appears earlier is rather intuitive and can be explained by the simple fact that coordination is a straight-forward way to bypass computation by accounting for items that are sent to storage (for instance, short-term memory) the way they appeared, without any correlation or hierarchy between them. This simplicity is likely to be successeful for at least a few items. Nevertheless, when there is a number of items that starts challenging memory capacity, a safer cognitive decision is to resort to structure, which exponentially increases memory and processing capacities (MILLER, 1956).
If items are organized hierarchically, then embedding computation, that is recursion, is a processing resource that once deployed might bring a reduction to the cost of combinatory computation. It might be costly to start the recursive structure, for instance:
Clearly the evaluation of most economical choices can be readily attested in adult language, but how do children acquiring language implement these choices?
In order to verify children’s processing of recursion, this study will focus on a highly recursive structure: prepositional phrases (PP) in Brazilian Portuguese. The aim here is to contrast PP recursion to PP coordination in acquisition. To do this, this research will try to assess children at the earliest moment that recursion of PPs becomes an available property of their grammar, so that coordination can be compared at this very point.
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An oral sentence picture matching test was produced to be applied to sixteen 3 y-o and sixteen 4 y-o children, following a between-subject distribution. Children heard a sentence and had to match it with one of two pictures: one depicted a situation of a coordinated list and the other depicted a situation of embedded nouns hierarchically organized.
The prosodic contour of phrases was controlled, using PRAAT platform6, such that the only cue used for interpretation was syntactic. We left no pauses and suppressed all prosodic modulation, so that there were no biases that could confound participants.
Using a preferential looking paradigm, participants listened to test sentences either in the recursive or coordination condition. For instance, in the recursive condition:
Then, when listening to the test sentence, children had to point toward the best match. All the while, there was a camera filming children’s gestures from behind, so that the experimenters could have an after-test response control, besides the register taken down by the experimenter’s assistant during the test.
In this experiment, participants listened to test sentences either in the recursive or coordination conditions For instance, in the recursive condition:
When children clearly and resolutely pointed to one of the pictures, experimenters would count the response as relating to a coordinated or a recursive interpretation. Thus, if participants in each one of the two age groups were able to process and to correctly interpret the recursion of PPs, there would be more pointing toward the images representing the recursion, when they listened to the recursive sentences and more pointing responses toward the images representing coordination, when they listened to the coordinated sentences.
The number of recursive layers and that of coordinated items were also controlled for. There were sentences with to or three recursive layers and coordinated items, as it can be seen in the examples below:
· Recursive sentence with two embeddings
(There is cat in the box on the bed)
· Recursive sentence with three embeddings
(There is pig in the bucket on the tray on the chair)
· Coordinated sentence with two items
(There is apple in the box and in the bucket)
· Coordinated sentence with three items
(There is dog in the box and in the bucket and on the chair)
Thirty-six children, native speakers of Brazilian-Portuguese participated in this experiment. They were divided into two age groups: the 3-year-old group (2,9 to 3,8; M =3,5;
Children were tested in two public preschools in Rio de Janeiro, and their parents signed an informed consent form. An additional eight children participated in the study, but were not included in the final analysis because they were not concentrated on the task during the experiment (4), there were experimental problems (2), or there was some kind of fussiness during the experiment session in the school (2).
Eight pairs of experimental sentences were created from eight target words likely to be known by children, for example:
Children were tested individually in their own preschool. During the experiment, participants were seated in front of a computer screen displaying the visual stimuli.
They were told that they were going to play a game in which they would have to find the image that corresponded to the sentences they would listen to.
The experiment started by a practice session consisting in a presentation of a filler sentence that corresponded to one of the two pictures simultaneously presented to them (Figure 2).
As soon as the participant gave two correct pointing responses in this practice session, the experimenter would start the test session.
Before the test session began, the experimenter would adjust headphones to the children’s ears. The test session was composed of si[teen trials: eight test sentences and eight filler sentences, half of the test sentences with a recursive structure and half with a coordinated structure counterbalanced between participants.
Each test trial started by an inspection period to provide the child enough time to look at the pair of images displayed on the screen. Each image was first presented separately for 5 seconds on the left or the right side of the screen, and a neutral audio prompt was played at the same time, for instance:
Responses that correctly matched the target interpretation of the sentences (recursive in recursive condition, coordination in coordination condition) were scored as 1, and incorrect responses were scored as 0 (See Appendix 2). Thus, for each child and for each condition, we calculated the average scores of their responses and used them as the dependent measure in our analysis.
Because recursive and coordination responses in this task are complementary, we chose the proportion of pointing toward the recursive image as our dependent measure in the statistical analysis.
Figure 4 presents the average proportion of pointing responses toward the recursive and the coordination images for each condition (Recursive or Coordination) for both groups of children (3-year-old Vs. 4-year-old).
A one-way analysis of variance (ANOVA) was conducted with participants as random factor. This analysis included a within-subject factor Condition (Recursive, Coordination), and two between-subjects factor, List (List1, List2) and Group (3 year old, 4 year old).
A main effect of Condition (F(1,34) = 6.38, p < .02) was observed. Taking all together, children pointed more toward the coordination image than to the recursive image when they heard the coordinated sentences. There was also a marginally significant effect of Group (F(1,34) = 3.92, p = .055) indicating that while 4-year-old children pointed more toward the recursive image than toward the coordination image when they heard the test sentences with the recursive structure (and vice-versa for the test sentences with the coordinated structure), 3-year-olds always pointed more toward the coordination image for both conditions (recursive, coordination). Thus, the proportion of pointing responses toward the recursive image in the recursive condition was above chance for 4-year- olds (60%), but for 3-year-old children the average was below chance (40%), (t(34) = -3.164, p < .01). No other effect or interaction reached significance.
The main effect of the test points to the fact that the children tested at 3 and at 4 years of age appear to have the coordination interpretation available to them. One might argue that this test cannot properly disentangle coordination from a simple lexical effect: children might stock semantic contents of the items presented to them without really coordinating them. Nevertheless, even the simple adding of one layer of PP already entails a syntactic merge between a DP and a PP (a pencil in the bo[), or even a simplified merge (pencil in bo[).
The fact that they recognize the coordinated condition in which there is a distribution of items, for instance:
As a contrast, the recursive condition is more complex and cannot be confounded with mere memory storage, because such sentences necessarily entail hierarchical structures that yield meaning on their own, independently from the le[ical properties. When the recursive figure was correctly matched to its corresponding sentence, that meant that the child knew that a single object was nested in two or three containers. That is, the distributive reading was blocked.
The recursive structure appeared to be meaningful to the children tested as of 4 years of age (Check the two last columns in Figure 4). Four year olds pointed more to the recursive pictures than to coordinated ones when they listened to recursive sentences. Thus, this test successfully identified the transition period when PP recursion became a meaningful computation to children.
The number of recursive layers – two or three – was not a significant factor, statistically speaking. Nevertheless, since 3 year-olds do not appear to use PP recursion meaningfully, and they were tested for layers together with 4 year-olds, another test focusing on 4 year-olds and multiple layers as a factor should be applied, in order to verify if their acquired computation seems to be similar to that of adults in this respect.
Currently, we are developing a semantic investigation of manner PPs, conveying different thematic roles, and we expect to get the very same results as those of the place PPs already tested here, since recursion is a syntactic computation and should not be hindered or facilitated by the semantic content of the phrase. We also intend to test acquisition of other recursive phrases in a similar fashion.
Most importantly, since 4 years of age is the moment that PP recursion seems to become available, several types of recursive computations must be tested involving other cognitive domains, so that it is possible to fare if recursion of PPs and of other linguistic structures, arising from interface effects, derive from more primitive properties than those verified in linguistic computations.
In terms of more sophisticated perspectives, a desirable advancement, as much as it is hard to accomplish with children, is the use of online testing, that can discriminate between automatic and reasoned upon processes.
ARSENIJEVIC, B.; HINZEN, W.
CHOMSKY, N.
EVERETT, D.
EVERETT, D.
FITCH, W. T.; HAUSER, M. D.; CHOMSKY, N.
HAUSER, M. D.; CHOMSKY, N.; FITCH, W. T.
MAIA, M. et al.
M ILLER, G. A.
NEVINS, A.; PESETSKY, D.; RODRIGUES, C.
PÉREZ-LEROUX, A. T. et al.
ROEPER, T.
ROEPER, T.; SNYDER, W.
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List1 | Test1 | Cat - Gato | Recursive | Tem gato na caixa na mesa. |
List1 | Filler1 | Dog - cachorro | F1 | O cachorro está no barco |
List1 | Test2 | Apple - Maça | Coordination | Tem maçã na caixa e no balde |
List1 | Filler2 | Little cat - gatinho | Filler | O gatinho subiu no telhado |
List1 | Test3 | Pig - Porco | Recursive | Tem porco no balde na bandeja na cadeira . |
List1 | Filler3 | Rabbit - coelho | Filler | Hoje é o aniversário do coelho |
List1 | Test4 | Banana - Banana | Coordination | Tem banana na caixa e na bandeja e na cadeira |
List1 | Filler4 | Apple - maça | Filler | Quem botou a maçã no livro? |
List1 | Test5 | Cake - Bolo | Recursive | Tem bolo na bandeja na mesa |
List1 | Filler5 | Pig - porco | Filler | O porco vai comer os morangos. |
List1 | Test6 | Dog - Cachorro | Coordination | Tem cachorro na caixa e no balde e na cadeira |
List1 | Filler6 | Strawberries - morangos | Filler | A caixa de morango está cheia. |
List1 | Test7 | Sandwich - Sanduiche | Recursive | Tem sanduiche na caixa no balde na mesa |
List1 | Filler7 | House - casa | Filler | Será que o porco vai entrar na casa? |
List1 | Test8 | Rabbit - Coelho | Coordination | Tem coelho no balde e na cadeira |
List1 | Filler8 | Dog and Cat - Cão_e_gato | Filler | O cachorro e o gato subiram na mesa. |
List2 | Test1 | Cat - Gato | Coordination | Tem gato na caixa e na mesa |
List2 | Filler1 | Dog - cachorro | F1 | O cachorro está no barco |
List2 | Test2 | Apple - Maça | Recursive | Tem maça na caixa no balde |
List2 | Filler2 | Little cat - gatinho | Filler | O gatinho subiu no telhado |
List2 | Test3 | Pig - Porco | Coordination | Tem porco no balde e na bandeja e na cadeira |
List2 | Filler3 | Rabbit - coelho | Filler | Hoje é o aniversário do coelho |
List2 | Test4 | Banana - Banana | Recursive | Tem banana na caixa na bandeja na cadeira |
List2 | Filler4 | Apple - maça | Filler | Quem botou a maçã no livro? |
List2 | Test5 | Cake - Bolo | Coordination | Tem bolo na bandeja e na mesa |
List2 | Filler5 | Pig - porco | Filler | O porco vai comer os morangos. |
List2 | Test6 | Dog - Cachorro | Recursive | Tem cachorro na caixa no balde na cadeira |
List2 | Filler6 | Strawberries - morangos | Filler | A caixa de morango está cheia. |
List2 | Test7 | Sandwich - Sanduiche | Coordination | Tem sanduiche na caixa e no balde e na mesa |
List2 | Filler7 | House - casa | Filler | Será que o porco vai entrar na casa? |
List2 | Test8 | Rabbit - Coelho | Recursive | Tem coelho no balde na cadeira |
List2 | Filler8 | Dog and Cat - Cão_e_gato | Filler | O cachorro e o gato subiram na mesa. |
This research was supported by a Productivity in Research grant from CNPq (National Council of Scientific and Technological Development), bestowed to Aniela Improta França; a research grant from the Rio de Janeiro Carlos Chagas Filho Foundation for Research Support (FAPERJ), bestowed to Aleria Lage; and an undergraduate fellowship from CNPq bestowed to Mayara de Sá Pinto. This work would not have been possible without the support of the wonderful staff of the public preschools Espaço de Desenvolvimento Infantil Moacyr de Goes and Espaço de Desenvolvimento Infantil Professora Solange Conceição Tricarico, located in Maré community, in Rio de Janeiro.
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