Which category replaces an omitted clitic? The case of European Portuguese Introduction.

Costa, João, Maria Lobo e Carolina Silva. No prelo. Which category replaces an omitted clitic? The case of European Portuguese. In P. Larranaga e P. Guijarro-Fuentes (eds.). Pronouns and Clitics in Early Language. Berlin: Mouton de Gruyter Which category replaces an omitted clitic? The case of European Portuguese João Costa, Maria Lobo & Carolina Silva CLUNL/FCSH/Universidade Nova de Lisboa 1. Introduction. A well known fact about child language is that pronominal clitics are omitted in children s early productions in many languages (cf. Jakubowicz et al. 1998, Wexler, Gavarró & Torrens, 2003; Tsakali & Wexler, 2003; Babyonyshev & Marin, 2005, among others). There is less consensus regarding the universality of clitic omission. For instance, in Spanish, there is an ongoing debate regarding the existence of omission and its duration (cf. e.g. Castilla et al. 2008). In recent work, we contend that there is evidence to claim that clitic omission is not a uniform phenomenon (Costa, Lobo & Silva 2009, Costa & Lobo 2010). Another area in which there is little consensus and not much discussion is on the nature of the (empty) category replacing the omitted clitic in languages with omission. The goal of this paper is twofold: first, we review previous work on clitic production by children acquiring European Portuguese, showing that there is omission in this language. Second, we contribute to the debate regarding the nature of the empty category, by arguing that children acquiring European Portuguese produce a null object, as in the target adult grammar, when they fail to produce a clitic. Based on this discussion, we try to find evidence for or against continuity in the representation of the null object in child language, by inspecting whether it is a pro, a variable or whether children s omissions of complements might be target deviant instances of VP-ellipsis. This paper is organized as follows: in section 2, some background information on clitics and null objects in European Portuguese is provided. Section 3 presents the results of previous studies on the production of different types of clitics by children acquiring European Portuguese. Section 4 discusses a set of comprehension experiments confirming the idea that European Portuguese speaking children know that the language has null objects. Finally, in section 5, we present some preliminary results of a study aiming at determining whether European Portuguese children know the nature and properties of the empty category involved in the null object construction.

2. Clitics and null objects in European Portuguese. Like other Romance languages, European Portuguese has pronominal clitics. Clitics can be accusative, as in (1a), but also dative (1b), reflexive (1c), or non-argumental (1d): (1) a. O Pedro viu-o. the Pedro saw it/him acc Pedro saw it/him. b. O Pedro deu-lhe um livro. the Pedro gave him/her dat a book Pedro gave him/her a book. c. O Pedro lavou-se. the Pedro washed-se refl Pedro washed himself. d. O Pedro porta-se mal. the Pedro behaves-se inherent bad Pedro behaves badly. Some clitics vary in gender, person and number. This is shown for the accusative clitic in (2) and (3): (2) Number and gender variation a. O Pedro viu-o. Masculine singular the Pedro saw him acc/masc Pedro saw him. b. O Pedro viu-a. Feminine singular the Pedro saw her acc/fem c. O Pedro viu-os. Masculine plural the Pedro saw them acc/masc

Pedro saw them. d. O Pedro viu-as. Feminine plural the Pedro saw them acc/fem (3) Person variation a. O Pedro viu-me. 1st person singular the Pedro saw me acc b. O Pedro viu-te. 2nd person singular the Pedro saw you acc c. O Pedro viu-o. 3rd person singular the Pedro saw him acc d. O Pedro viu-nos. 1st person plural the Pedro saw us acc e. O Pedro viu-vos. 2nd person plural the Pedro saw you acc f. O Pedro viu-os. 3rd person plural the Pedro saw them acc Unlike what happens in the majority of Romance languages, clitics are not always proclitic. Depending on the syntactic environment, clitics can be proclitic, enclitic or mesoclitic. As stated in Duarte & Matos (2000), there is a limited set of proclisis triggers, and enclisis functions as an elsewhere environment. Mesoclisis is restricted to future and conditional inflection, and occurs in enclisis contexts. In (4), we list the set of proclisis triggers (cf. Duarte & Matos 2000). In (5), an example of proclisis, enclisis and mesoclisis is given. (4) Proclisis triggering environments: Negation Wh-questions Embedded sentences with a lexical C Certain adverbs in preverbal position Preverbal quantified subjects Affective operators

(5) a. Proclisis Eu não te vi. I not you saw I didn t see you. b. Enclisis Eu vi-te. I saw you I saw you. c. Mesoclisis Eu ver-te-ei. I see-you-fut I will see you. Besides clitics, European Portuguese also has null objects (Raposo 1986). A null object construction can be used in the exact same pragmatic environment in which a clitic is legitimate: whenever the referent is given information: (6) A: E o Pedro? What about Pedro? B: a. Não o vi. Not him saw I haven t seen him. b. Não vi. Not saw I haven t seen him. As described in Raposo (1986) and Costa & Duarte (2003), null objects do not always freely alternate with clitics. In reflexive contexts, null objects are ruled out (7): (7) A: E o Pedro? What about Pedro? B: a. Não se lavou.

Not SE washed He hasn t washed himself b. *Não lavou. Not washed The same holds for 1 st and 2 nd person clitics. (8) illustrates this for 1 st person: (8) A Maria viu*(-me). the Maria saw me Maria saw me. The availability of the null object construction is also constrained by certain syntactic environments. As argued in Raposo (1986), null objects are ruled out in strong island environments: (9) A: E o Pedro? What about Pedro B: a. *Fiquei aborrecido quando abracei. Got annoyed when hugged b. Fiquei aborrecido quando o abracei. Got annoyed when him hugged I got annoyed when I hugged him. The observation that null objects are ruled out in strong island contexts motivates Raposo s (1986) proposal that null objects are variables. As such, they cannot be bound by a topic operator in the matrix sentence across a strong island boundary. Pronominal forms, instead, can establish coreference relations across islands. We will return to the different properties of pronouns and variables below. For the time being, it is enough for us that the reader keeps in mind the idea that the null object is a variable, which explains its limited distribution and its ungrammaticality in contexts like islands a context in which pronouns cannot be bound. The main aspects to be retained from this sketchy description of the behavior of clitics and null objects in European Portuguese are:

a) European Portuguese has pronominal clitics, like other Romance languages; b) European Portuguese clitics vary in syntactic function, gender, number and person; c) European Portuguese is a null object language; d) In certain environments, null objects freely alternate with clitics; e) In specific environments, null objects are ruled out; f) The analysis of null objects as variables explains their sensitivity to strong island environments. Given this description, it should be clear now that, for the learning child, acquiring clitics in this language involves, at least, detecting its form and functions, finding out that the clitic can alternate with a null object, and discovering the correct distribution of null objects, partly by determining the nature of the empty category involved in null object constructions. 3. Clitic production in the acquisition of European Portuguese. In a series of studies by Ken Wexler and associates (Wexler, Gavarró & Torrens, 2003; Tsakali & Wexler, 2003; Babyonyshev & Marin, 2005), it is argued that children omit clitics in early stages of acquisition, but omission is not universal. These authors argue that it correlates with the availability of past participle agreement in the language. For instance, French is a language with past participle agreement (10), and as such it is expected to have clitic omission: (10) a. Les fenêtres Je les ai repeintes. The windows I them ACC-FEM-PL have repainted- FEM-PL The windows. I repainted them. Spanish, on the other hand, does not have past participle agreement (11), and is not expected to have clitic omission: (11) a. Las ventanas las he repintado The windows I them ACC-FEM-PL have repainted- MASC-SG

The windows. I repainted them. These authors proposal predicts that there should be no clitic omission in European Portuguese, since this language patterns like Spanish in what concerns past participle agreement. In a series of studies (Costa & Lobo 2006, Silva 2008, Carmona & Silva 2007, Costa, Lobo, Silva & Carmona 2008), we tested this prediction and found no evidence to support it, because children acquiring European Portuguese do omit clitics. However, two problems arise: first, the rates of omission were not comparable to those found for other languages. It was found that children acquiring European Portuguese omit more than children acquiring other languages with omission, and that omission lasts longer than in other languages, since 5 year olds still display a certain rate of omission, whereas in other languages, omission rates drop much earlier. In Varlokosta et al. (in preparation), a comparative work on 16 languages, it becomes obvious that omission rates are higher in Portuguese than in other languages. In this study, it is shown that children acquiring European Portuguese, at the age of 5, produce 20% of their sentences with clitics, whereas Italian and Catalan children, at the same age, and in the same experimental setting, produce 92,9% and 98% of clitics, respectively. The second problem is that the data do not receive a self-evident interpretation. Recall that European Portuguese has null objects. As such, when a child utters a sentence without a clitic, one does not know whether the child is omitting a clitic as in other languages, or producing a target null object construction. In order to find the source of the problem, we tested a wider range of clitics. In particular, we decided to test the production of clitics in contexts in which null objects are ruled out in order to determine whether the children omit in accordance with a target null object grammar. If so, their rates of omission should be nearly null in those contexts in which the clitic is compulsory. In the remainder of this section, we summarize the results obtained for clitic production of different types. The results presented come from Silva (2008, 2010). Following the elicitation procedure first used in Schaeffer (1997), and first adapted for European Portuguese in Costa & Lobo (2006, 2007), Silva (2008, 2010) tested 73 children aged between 3 and 6 years and 6 months old. The tests of clitic

production were also applied to a control group composed by 15 adults. The following table gives details on the children and adults tested: Children Mean age Female Male Total [3,0; 4,0[ 3 years and 7 months 11 4 15 [4,0; 5,0[ 4 years and 5 months 16 11 27 [5,0; 6,0[ 5 years and 6 months 9 12 21 [6,0; 6,5[ 6 years and 3 months 5 5 10 Total 41 32 73 Adults Mean age Women Men Total [24,0; 27,0[ 25 years and 2 months 9 6 15 Table 1: Participants information As just mentioned, the aim of Silva s study was to test different types of clitics, in order to assess correlations with the null object construction. As such, the following types of clitics were tested:

Tests per type of clitic Accusative Dative Reflexive Non-argumental Enclisis Proclisis Islands Enclisis Proclisis Islands Enclisis Proclisis Enclisis Proclisis 1 st Sing 1 st Sing 1 st Sing 1 st Sing 1 st Sing 1 st Sing 1 st Sing 1 st Sing 1 st Sing 1 st Sing 1 st Plur 1 st Plur 1 st Plur 1 st Plur 1 st Plur 1 st Plur 1 st Plur 1 st Plur 1 st Plur 1 st Plur 2 nd Sing 2 nd Sing 2 nd Sing 2 nd Sing 2 nd Sing 2 nd Sing 2 nd Sing 2 nd Sing 2 nd Sing 2 nd Sing 2 nd Plur 2 nd Plur 2 nd Plur 2 nd Plur 2 nd Plur 2 nd Plur 3 rd Sing, fem 3 rd Sing, masc 3 rd Sing, fem 3 rd Sing, masc 3 rd Sing, fem 3 rd Sing, masc 3 rd Sing 3 rd Sing 3 rd Sing 3 rd Sing 3 rd Sing 3 rd Sing 3 rd Sing 3 rd Plur, fem 3 rd Plur, masc 3 rd Plur, fem 3 rd Plur, masc 3 rd Plur, fem 3 rd Plur, masc 3 rd Plur 3 rd Plur 3 rd Plur 3 rd Plur 3 rd Plur 3 rd Plur 3 rd Plur Table 2: Conditions tested in the experiment. As can be seen in the table, the conditions include those contexts in which clitics and null objects alternate, and those in which only clitics are a valid option. Two elicitation procedures were used. For 1 st and 2 nd person clitics, a puppet interacted with the child and with some toys. For 3 rd person clitics, the clitics were induced through the presentation of pictures. Both procedures had in common the relevant fact that the referent for the pronoun was made highly accessible. Below, we present an example for each of the procedures taken from Silva (2010):

Experiencer: What will Grandma do?! Grandma: I can smell something But I don t know what it is Are you both wearing perfume? Let me smell you [Grandma smells the child and the Puppet] Hmmm! You smell so good! Puppet: Estava distraído! Não reparei no que a Avó fez. Como é que ela sabe que nós cheiramos bem?! Diz lá o que a Avó fez? I was distracted! I didn t pay attention to what Grandma did. How does she know we smell good?! Tell me what did she do? EXPECTED RESPONSE: Cheirou-nos. She smelled us. Figure 1: Example of test item for eliciting 1 st person clitics. Experiencer (1 st Image): These 3 boys are dirty because they played football in the mud. But look! Each one of them has a towel in his hand. Experiencer (2 nd Image): [Pointing to the drawing] Este menino usou esta toalha e está agora limpo. Mas estes 2 continuam sujos. O que é que eles não fizeram? This boy used this towel and now he s clean. But these 2 boys are still dirty. What didn t they do? EXPECTED RESPONSE: Não se limparam. They didn t clean themselves. Figure 2: Example of test item for eliciting 3 rd person clitics.

For a detailed presentation of the results for each and every condition, we refer the reader to Silva (2008, 2010). For the purposes of this paper, it is sufficient that we focus on the results obtained in the 3 rd person accusative condition the clearest case in which clitics and null objects are in free variation, comparing them with a summary of results in which clitics should be obligatorily produced. Let us start by considering the results for the 3 rd person (singular and plural) accusative condition in non-compulsory contexts (enclisis and proclisis) summarized in table 3: 3 rd PERSON ACCUSATIVE CLITICS Clitic [3,0; 4,0[ [4,0; 5,0[ [5,0; 6,0[ [6,0; 6,5[ 23/240 99/432 146/336 74/160 9,58% 22,92% 43,45% 46,25% Control group 229/240 95,42% Null form 210/240 298/432 149/336 84/160 3/240 87,50% 68,98% 44,35% 52,50% 1,25% DP 6/ 240 33/432 41/336 2/160 8/240 2,50% 7,64% 12,20% 1,25% 3,33% Strong pronoun 1/240 0,42% 2/432 0,46% 0/336 0% 0/160 0% 0/240 0% Table 3: Results for 3 rd person accusative clitics in non-compulsory contexts. Two major conclusions emerge from these results. First, children s production of clitics is different from what adults do (chi-square tests: p < 0.001 for all comparisons between each children s group and the control group). There is an evident development effect from 3 to 5 years old (chi-square tests: p < 0.001). From 5 to 6, the development is much slower (chi-square test: p = 0,897). However, at age 6 the rate of production is still far from what is observed for adults 1 (as mentioned above, chi-square test: p < 0.001). Second, as was referred before, it is not the case that clitic omission ceases 1 The adults were, possibly, sensitive to the experiment since a higher production of null objects was expected in contexts where they freely vary with clitics.

at around age 3, as argued for other languages. Recall, however, that these data do not allow us a clear interpretation of the facts as clitic omission, since the null form row may be read as a case for assuming that children produce target null objects. More revealing data comes in the following table, containing a synthesis of the results for those contexts in which clitics are obligatory and null objects are ruled out. 3 rd PERSON ACCUSATIVE CLITICS IN STRONG ISLANDS Clitic [3,0; 4,0[ [4,0; 5,0[ [5,0; 6,0[ [6,0; 6,5[ 4/120 33/216 49/168 32/80 3,33% 15,28% 29,17% 40% Control group 78/120 65% Null form 77/120 64,17% 76/216 35,18% 27/168 16,07% 20/80 25% 0/120 0% DP 38/120 107/216 92/168 28/80 42/120 31,67% 49,54% 54,76% 35% 35% Strong pronoun 1/120 0,83% 0/216 0% 0/168 0% 0/80 0% 0/120 0% Table 4: Results for 3 rd person accusative clitics in strong islands (compulsory contexts). The results of these tables are interesting. First, they reveal that clitics are also omitted in contexts in which null objects are ruled out. However, they show that the rate of omission is lower in compulsory contexts than in non compulsory contexts: [3,0; 4,0[ - 87,50% vs. 64,17%; [4,0; 5,0[ - 68,98% vs. 35,18%; [5,0; 6,0[ - 44,35% vs. 16,07%; [6,0; 6,5[ - 52,50% vs. 25 %. In Costa & Lobo (2006), the fact that children omit clitics even in contexts in which null objects are ruled out was taken as an indication that there is clitic omission different from the target null object construction in children s productions. However, this account failed to provide an explanation for why there were different rates of omission, and did not make any commitment as to the nature and category of the empty element in the contexts in which clitics were not produced.

In fact, in the absence of a clitic, several outcomes are possible: either the child produces a kind of truncated structure and no empty category is involved, or the child is filling in the object position with some kind of empty category. The first hypothesis predicts that children treat structures without a complement as intransitive, whereas the second one predicts that children know that the relevant structures are transitive. In other words, under the second hypothesis, children know how to interpret null object constructions. If the second alternative is on the right track, one still has to know what type of null object is involved: a pronominal or a variable. Summarizing, the results obtained in the studies on children s production of clitics in European Portuguese open up space for a certain degree of analytical indeterminacy. The options are: a) Children omit clitics in compulsory contexts, because they have clitic omission of the type found in other languages. b) Children omit clitics in compulsory contexts, because they know that European Portuguese is a null object language, but they overuse null objects. In order to decide between these two options, some comprehension tests were run, in order to understand whether children acquiring European Portuguese display knowledge on the existence of the null object construction. If they do not, the second hypothesis can be immediately discarded. In the next section, we briefly present the results of the experiments carried out in Costa and Lobo (2008, 2010), which try to provide answers to this issue. 4. Null objects in comprehension. French children are known to omit clitics. Grüter (2006) raised a question for French quite similar to the one we raised for European Portuguese: can it be that French children are producing a kind of null object construction? If so, as conjectured by Grüter (2006), this means that their grammar includes the possibility of generating transitive structures without an explicit element. As such, they are supposed to interpret a verb

without a complement transitively. In order to test this prediction, Grüter (2006) developed a test in which children were asked to judge the truth value of verbs without a complement in transitive contexts. Children acquiring French massively rejected transitive interpretations for verbs that did not appear with any type of complement. This result can be interpreted as a consequence of the absence of a null object construction in their grammar. Costa and Lobo (2008, 2009) adapted Grüter s test for European Portuguese, and assessed whether children could assign transitive interpretations to a verb without a complement in the following environments: a) Simple clauses; b) Strong islands; c) Reflexive contexts. The purpose of testing environment a) is twofold: first, it allows for a clear comparison with the results obtained for French; second, it allows us to determine whether children acquiring European Portuguese have null objects. Environments b) and c) are those in which null objects are illegitimate in the adult grammar (out of these, only environment b) was tested for French, and no differences were found with respect to context a)). Testing the comprehension of verbs without a complement is interesting, since one can assess consistency between production and comprehension, and add a further argument to the idea that omission in European Portuguese is a case of overuse of the null object construction. In order to test the comprehension of null objects, Grüter s test was adapted to European Portuguese. In this test, a selection of verbs that can be either intransitive or transitive are used. A transitive situation is presented with a sentence describing it (uttered by a puppet) containing only subject and verb. If the child s grammar has no null objects, the child must judge such description false. If, on the other hand, the child s grammar includes null objects, she will accept a sentence with no explicit internal argument, considering it true. Let us consider two examples of test items: a potentially ambiguous sentence is presented to the child in a context making one of the interpretations true or false. After

the presentation of an image, the child is asked to judge whether a sentence uttered by the puppet is true or false. In the test items, the following transitive/intransitive alternation verbs were used: mergulhar dive ('x mergulha' or 'x mergulha y'), adormecer fall asleep / put to sleep ('x adormece' or 'x adormece y'), acordar wake up ('x acorda' or 'x acorda y'), baloiçar swing ('x baloiça' ou 'x baloiça y'). As shown in the following examples, both uses are possible for all these verbs: (12) a. O Rui mergulhou. the Rui dove Rui dove. b. O Rui mergulhou o irmão na piscina. the Rui dove the brother in the pool Rui put his brother in the pool (13) a. O Rui adormeceu. The Rui fell asleep Rui fell asleep. b. O Rui adormeceu o bebé. The Rui fell asleep the baby Rui put the baby to sleep. (14) a. O Rui acordou. The Rui woke up Rui woke up b. O Rui acordou o bebé. The Rui woke up the baby Rui woke up the baby. (15) a. O Rui baloiçou na cadeira. The Rui swang in the chair Rui swang in the chair. b. O Rui baloiçou o bebé na cadeira.

The Rui rocked the baby in the chair Rui rocked the baby in the chair. The test was preceded by a familiarization period with the task, with the puppet, with the images and with the verbs used in both variants (transitive and intransitive). In the period of adaptation to the experimental setup, the images were presented to the child and the four verbs were used in the transitive and in the intransitive constructions in order to ensure that the verbs, in their different constructions, were known to the child, and in order to make the interpretation of the drawings easier. In the following set of images, one can see the type of material used in the elicitation of judgements on null objects in reflexive environments: Figure 3: Example of pictures used in the comprehension of null objects For these images, the experimenter first introduces the characters, and then he describes the situation in the first drawing making the characters highly available in the discourse scale. Then, the puppet would utter a sentence like He is washing (without the reflexive clitic), which is not a legitimate description for the rightmost image. The results of this experiment, run on 19 children aged between 3;6 and 5;9, are summarized in the following graph, in which the rates of adult-like responses are given 2 : 2 Pron (V): Condition for pronouns with pronominal interpretation (True); Pron=Refl (F): Condition for pronouns with reflexive interpretation (False);Refl (V): Condition for reflexives with reflexive interpretation (True); Refl=Pron (F): Condition for reflexives with pronominal interpretation (False); ON

3;6-5;9 (n=19) 100% 80% 60% 40% 20% 0% Pron (V) Pron=Refl (F) Refl (V) Refl=Pron (F) ON (V) ReflN (F) DP (V) TransRefl (F) Pron (V) Pron=Refl (F) Refl (V) Refl=Pron (F) ON (V) ReflN (F) DP (V) TransRefl (F) Graph 1: Rates of correct comprehension of pronouns, reflexives and null arguments The most important conditions to focus on in the graph are ON(V), in which we tested the comprehension of null objects in simple sentences, and REFLN(F), the condition in which null objects should be ruled out. As can be read off the graph, children are successful in the mastery of null objects in simple transitive clauses. This is obvious, given the high success rate in the interpretation of transitive verbs without a complement as transitive. This contrasts with the behavior of children acquiring French described in Grüter (2006). The comparison between ON(V) and REFLN(F) shows that children fail to understand that reflexives are not good candidates for null objects. Note that no clear individual differences were found, and, as such, the difference between these two conditions is quite strong. These results are consistent with the results obtained in production tasks. Recall that children fail to reject the ungrammatical structures that they produce. From these observations, several interesting conclusions can be drawn: a) First, it becomes obvious that omission is not a uniform phenomenon, since different speakers display different behaviors towards omission. In particular, in French, no acceptance was found in these contexts, very much (V): Condition with accusative null objects (True); ReflN (F): Condition with null reflexive (False); DP (V): Control condition with full DP (True); TransRefl (F): Control condition with full DP and reflexive interpretation (False).

differing from European Portuguese. As such, it is legitimate to conjecture that the high rate of omission in this language is due to the overuse of null objects, whereas in French the inability to judge the same kind of stimulus transitively reflects that no null object grammar is at play. b) Second, the hypothesis that the high rates of omission found in European Portuguese are due to an overuse of the null object construction is confirmed, since the contexts of illegitimate production and comprehension overlap. c) Third, the rate of illegitimate acceptance of null objects in reflexive contexts is very similar to the rate of illegitimate acceptance of null objects in strong islands, found in Costa & Lobo (2008). This consistency in results again parallels what has been found in production. If the analysis we are proposing is on the right track, the combination of the results from production and comprehension converge in showing that children know that European Portuguese is a null object language, and overuse the null object option. If that is so, the differential behavior in clitic production, when this language is compared to others, can be easily explained: the rate of clitic omission and the ages at which children converge with the control group are different from what has been found for other languages, because clitic omission in this language is of a different nature. Unlike in other languages, clitic omission in European Portuguese is a kind of null object construction. Note that this is an interesting result, since it confirms the idea that much of the syntactic knowledge is acquired very early (Wexler 1998), and gives support to the claim there is great continuity between child and adult grammar (Guasti 2002). However, note that the evidence referred to so far does not yet provide a crystal-clear answer regarding the nature of the empty category involved. One possibility raised in Silva (2010) is that the null category assumed by children is a pro, and not a variable. This would explain why there are more contexts in which the null object is allowed for the child than for the adult. What is at stake, then, is to determine the degree of continuity involved in the mastery of the null object construction. Do children posit the same empty category as adults? For children, is the null object a pro or a variable? If the null object is pro, the

degree of continuity is smaller than one might think. Still another option, available in the target grammar is that children use a VP-ellipsis construction (as in example 16a). VP-ellipsis differs from null object in that it is allowed in islands (16b), with reflexives (16c), and it requires verbal parallelism (16d) (Matos 1992) 3 : (16) a. O Pedro tinha escrito o artigo e eu também tinha. The Pedro had written the article and I also had Pedro had written the article, and I had too. b. O Pedro escreveu o artigo, porque eu também escrevi. The Pedro wrote the article because I also wrote Pedro wrote the article, because I also did. c. O Pedro lavou-se e eu também lavei. Pedro washed SE and I also washed Pedro washed himself, and I did too. d. *O Pedro comprou o livro, porque eu roubei. The Pedro bought the book, because I stole The pilot study presented in the next section tries to shed some light on the nature of the null category involved in children s performances. 5. Null object: pro, variable or ellipsis? As discussed in the previous section, there is good evidence for saying that clitic omission in child Portuguese is an overuse of the null object option, independently available in the target grammar. If this analysis is on the right track, there is continuity between children s knowledge and the properties of adult grammar. However, in order to determine the degree to which child language and adult grammar are alike, it is 3 Santos (2006), unlike Matos (1992), rejects the idea that VP-ellipsis requires verbal identity. The fact that sentences like (16d) are ungrammatical is a standard argument to distinguish VP-ellipsis and null objects, since there is no verbal identity, and the ellipsis is illegitimate, because of the island context. If, on the contrary, a relaxation of the identity requirement were possible, this sentence should be fine under a VP-ellipsis reading, since VP-ellipsis is allowed in island contexts. Since, in the experiment, we use cases similar to these ones, we will follow Matos in accepting the idea that VP-ellipsis requires identity.

important to find out whether the representation assumed by the child for null objects matches the one of adults. In order to do so, Costa & Lobo (2010a) developed a test enabling to establish whether children ascribe to null objects the interpretation expected if it is a variable. In this section, we present the test and explore some pilot results. This test is highly inspired in the findings of Miyagawa (2010), who described that pro and variables behave differently in anaphoric retrieval contexts. In particular, a null subject in an embedded environment cannot have a sloppy reading. This can be seen in the following example: (11) O Pedro disse que os pais iam a cavalo e o Rui disse que iam a pé. The Pedro said that the parents went on horse and the Rui said that went on foot Pedro said that his parents went on horse, and Rui said that his (parents) went by foot. Possible reading: Rui said that Pedro s parents went walking. Impossible reading: Rui said that his parents went walking. The only reading available for this sentence is the strict one, in which the null category retrieves the reference of the matrix antecedent. This contrasts with null objects: (12) O Pedro abraça os pais e o Afonso beija. The Pedro hugs his parents and Afonso kisses Sentence (12) is ambiguous, since the object can be co-referential with an antecedent from the first coordinate (in the case Afonso kisses Pedro s parents), or with Afonso s parents (in the reading in which Pedro hugs his parents, and Afonso kisses his parents). The first reading is generally known as strict, whereas the second one is known as sloppy.

Recall from the previous section that VP-ellipsis is another option to be considered in the interpretation of children s performances. As such, it is relevant to know how this construction behaves with respect to the strict/sloppy readings. As shown in (13), VP-ellipsis allows both strict and sloppy readings: (13) O Pedro abraça os pais e o Afonso também abraça. The Pedro hugs his parents and Afonso also hugs This sentence is ambiguous, since it can mean that Afonso hugs Pedro s parents (strict reading) or that he hugs his own parents (sloppy reading). Given this, it becomes obvious that the sole difference between null objects in simple sentences (as in 12) and VP-ellipsis in the same context is the requirement of verbal parallelism. Since we know that pro only allows for strict readings (Miyagawa 2010) (recall the description of the sentence in (11)), if a child consistently rejects sloppy readings for null object, there will be good reasons to assume that she does not know that the null object is a variable. If, on the other hand, the child knows that the null subject can only have strict readings, rejecting sloppy readings for it, and accepting them for null objects, we will have good evidence to postulate that children know the category of the null arguments they use. If the child gives non-adult answers for null subjects, accepting sloppy readings, however, we will have to assume that the interpretation of empty categories in child grammar is generally subject to development. In order to test this, Costa & Lobo (2010) developed a truth value judgment task testing the following conditions: a) Strict readings for null subjects (True); b) Sloppy readings for null subjects (False); c) Strict readings for null objects (True); d) Sloppy readings for null objects (True); e) Strict readings for VP ellipsis (True); f) Sloppy readings for VP ellipsis (True).

The test was designed in the following way: pictures of situations involving two children and their parents were presented to the participants. A puppet uttered a statement about the picture, which had to be judged true or false. The sentences were of the type illustrated in (11), (12) and (13). Consider, for instance, the following test item for condition a). The picture below was shown: Figure 4: Example of picture used in the strict/sloppy readings comprehension task The test sentence for this picture was: O Moreno disse que os pais estavam sentados e o Loiro disse que tinham chapéu. The dark hair kid said that the parents were sitting and the blond kid said that had hat The dark-haired kid said that his parents were sitting, and the blond kid said that they had a hat. This sentence is true, because only the strict reading is available for subject pro in the adult grammar. Let us now see an example of a test item for the null object condition under the sloppy reading. First, a picture like the following is shown:

Figure 5: Example of picture used in the strict/sloppy readings comprehension task The test sentence for this picture was: O Louro abraça os pais e o Moreno beija. The blond kid hugs the parents and the dark haired kid kisses The blond kind hugs his parents and the dark-haired kid kisses them. This sentence is true, because the sloppy reading is available for null object in adult grammar. In what follows, we present the results of a pilot of this test. In the pilot, 20 5 year old typically developing monolingual children acquiring European Portuguese, aged between 5;0 and 5;10 participated (8 boys and 12 girls). The mean age was 5;5. Children were tested individually in a quiet room. No response-contingent stimulus was given, and children were only rewarded after completion of the whole task. Data were coded and transcribed by two experimenters. Additionally, the test was ran on a control group consisting of 15 adults aged between 23 and 46 years old. The test contained 5 items for each of the conditions listed above (30 items for the sum of the whole conditions) and 17 fillers.

As can be seen in the following table, the adult control group performed as expected, associating sloppy readings with VP-ellipsis and null object only, and rejecting such sloppy reading in null subject contexts: %target responses Sloppy reading for null subject (False) 96% (72/75) Strict reading for null subject (True) 100% (75/75) Strict reading for null object (True) 100% (75/75) Sloppy reading for null object (True) 100% (75/75) Strict reading for VP ellipsis (True) 98,6% (74/75) Sloppy reading for VP ellipsis (True) 98,6% (74/75) Table 5: Results of the control group in the strict/sloppy readings comprehension test In the following table, we present the general results per condition for children: %target responses Sloppy reading for null subject (False) 51% (51/100) Strict reading for null subject (True) 64% (64/100) Strict reading for null object (True) 71% (71/100) Sloppy reading for null object (True) 71% (71/100) Strict reading for VP ellipsis (True) 69% (69/100) Sloppy reading for VP ellipsis (True) 86% (86/100) Table 6: Results for children in the strict/sloppy readings comprehension test These preliminary results from the pilot study are very interesting. As is clear from the results in the table, there is no clear difference between conditions. In fact, children have a poor performance in all conditions, and do not reach ceiling performances in any of them (unlike we found for adults, cf. Costa & Lobo 2010a). Crossing these results with those of previous experiments and the results of Santos (2006) for VP-ellipsis can help us understand this performance. First, one cannot argue that the bad results are a consequence of a lack of knowledge on null object, null subject or VP-ellipsis. Independent research reveals that children acquiring European Portuguese know null objects (cf. the studies mentioned in the previous sections). The same holds for null subjects, since they produce sentences with null subjects from early

on (Gonçalves 2005). Finally, Santos (2006) convincingly shows that children know VP-ellipsis, since they produce it in verbal answers to yes-no questions, and are able to retrieve the antecedent of an elided VP in simple contexts. In short, children s difficulties cannot be attributed to the inexistence of each of these constructions in their grammar. We contend that these data show that children have problems interpreting the null category involved in these constructions. In other words, they have null subjects, null objects, and VP-ellipsis, but fail to assign them an adult interpretation, and are not able to distinguish between strict and sloppy readings. If we go back to our original question - what is the nature of the category involved in children s object omissions? we are now closer to an answer. Three possibilities emerge: i) children use pro in object position, but do not know its interpretation; ii) iii) children use a variable in object position, but do not know its interpretation; children use a VP-ellipsis, and disrespect the requirement of verbal parallelism. Option iii) can be easily discarded on the basis of Santos (2006) results, since she showed that children s production of VP-ellipsis in verbal answers to yes-no questions provide positive evidence for compliance with the parallelism requirement. However, as shown by these results, their interpretation of VP-ellipsis is not target, since there are obvious differences between children s performance and the ceiling results of adults. Options i) and ii) can, actually, be merged, since, on the basis of the evidence we have, they cancel each other out. pro and variables can be distinguished on the basis of their distribution and interpretation. The data from previous experiments show that children annul the differences with respect to distribution, since they license an alleged variable in islands. The preliminary data from this pilot shows that they also annul the difference with respect to interpretation, since they assign pro readings typical of variables (the sloppy one), and they sometimes reject strict reading for null objects. Given this and on the basis of the data available so far, it is legitimate to state that the difference between pro and variables is irrelevant at this stage of language development.

Considering all this, one can hypothesize that for children to reach an adult knowledge of the types of null categories involved in subject and object position, they have to acquire the difference in interpretation that distinguish them, which arguably involves acquiring further properties distinguishing operator-variable relations from pronominal binding, a matter we leave for further research. 6. Conclusions. In this paper, we aimed at presenting a summary of previous results obtained in the study of clitic production by European Portuguese children. It was shown that the results of the production tasks indicated that clitic omission in European Portuguese is different from what occurs for other languages. As mentioned in previous studies, the results obtained for European Portuguese show that clitic omission is not a uniform phenomenon crosslinguistically, and, because of this, no clear conclusions may be drawn from the European Portuguese data in order to account for or against views of clitic omission like Wexler, Gavarró & Torrens (2003). We also showed that the results from comprehension studies provide good evidence to say that null objects are available early, and known to the children. This implicit knowledge of null objects provides further evidence for a different treatment of clitic omission, and is a good argument in favor of continuity in language acquisition. In order to determine the degree of continuity, we tested whether children master the difference between pro, variable and VP-ellipsis. Preliminary results from a pilot experiment indicate that children do not yet know the interpretive option associated with each one of these null constructions. As a consequence, we did not yet obtain crystal-clear evidence for determining the nature of the category involved in clitic omission contexts, but we are now able to say that the difference between pro and variable is not a relevant distinctive factor for children. This is promising as an explanation for the overuse of null object. By hypothesis, and comparing to the results obtained for VP-ellipsis (for which there is independent evidence for the early mastery of its syntax), we can suppose that children know the syntax of null subject and null object, and the only problem they have is in the assignment of the correct interpretation.

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