Why children prefer impossible worlds

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WHY CHILDREN PREFER IMPOSSIBLE WORLDS

LINGUE E LINGUAGGIO XII.2 (2013) 223–248


Vincenzo Moscati

abstract: Sentences with more than one logic operator are in principle ambiguous between different interpretations, depending on the assign-ment of logic scope. This aspect, largely overlooked in previous stud-ies, could provide the right distinction that we need to capture children’s early misinterpretation of epistemic negative sentences. Grounded on the notion of semantic strength (Horn 1989), the opposition between weak (e.g. might not) and strong (e.g. cannot) meanings will be introduced, in order to motivate the empirical prediction that an asymmetry be-tween different kinds of negative sentences should be observable in lan-guage development. This idea will be explored in two new experiments on Standard Italian, an ideal testing ground given its extremely simpli-fied modal paradigm. The results confirm the prediction that, at age five, children do not have problems in comprehending negative epistemic sen-tences in general. Experiments 1 and 2 show instead that difficulties are largely confined to weak negative sentences. An additional result, found in Experiment 1, is the difference between children and adults in posi-tive sentences. This result is accounted for in terms of focus and a related assertion of exhaustiVity. In Experiment 2, a contextual manipulation is introduced to test this hypothesis.

keywords: asymmetric entailment, exhaustivity, language acquisition, modality.

1. INTRODUCTION*

We continuously make inferences about the world and consider situations that may not be real. For this reason, natural languages require expressive means to talk about circumstances beyond the actual here and now. This fundamental property is at the core of human language and modality is one of the linguistic categories that permit us to talk about events which are not before our eyes. Given that modals are often used to refer to situations that

* I wish to thank Stephen Crain, Rosalind Thornton, Drew Khlentzos, Peng Zhou, Jacopo Romoli and two anonymous reviewers for their comments and helpful suggestions. A special thanks also goes to the members of the Language Acquisition Lab at Macquarie University, to Lena Dal Pozzo and Sarah Zizzo for their help in collecting the data and to the children, teachers and parents from the Scuola Materna Mameli and Kindergarten.

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are not immediately observable, an important question is how children learn their meaning and when they correctly master their complex semantics.

Notwithstanding the importance of this issue, the development of mo-dality it is still poorly understood and the picture is far from being clear. In particular, a long-standing debate concerns the stages in which the different meanings of modal expressions are acquired. One of the reasons is doubt-less the fact that modality is a complex category (Palmer 1986; Portner 2009) and that the widely used distinction (Lyons 1977) between epistemic and deontic modality is not always sufficient. For example, when these two kinds of modality have been compared, it is still unclear whether they de-velop in parallel or if one of them is favored over the other. In fact, while some authors have suggested an advantage of deontic modality over epis-ome authors have suggested an advantage of deontic modality over epis-temic modality (Piéraut-Le Bonniec 1980; Wells 1979; Perkins 1983), oth-ers have instead argued in favour of an essentially similar developmental trend (Hirst & Weil 1982; Byrnes & Duff 1989). However, important as it is, the modal base (e.g. deontic vs epistemic) is not the only factor at play in modal development. In fact, it is possible that some apparent inconsis-tencies found in the literature are due to other distinctions that have been overlooked in previous studies. I will argue that one of these distinctions concerns the interaction between modals and other logic operators, as for example negation.

It is well-known, at least since Wason (1965), that the presence of ne-gation poses an additional load on sentence processing. However, what is less well-known is the fact that the processing load associated with nega-tion increases in complex ways, depending on logic scope assignMent. In previous studies on early modal comprehension (Hirst & Weil 1982; Bas-Hirst & Weil 1982; Bas-celli & Barbieri 2002; Noveck 2001), an implicit assumption was that, in negative sentences, modals expressing possibility (e.g. can and may) pose the same grade of difficulty. In this paper, I will question this assumption on the basis of the fact that the two sentences John may not come and John cannot come convey a very different meaning: while the former expresses the possibility that a certain event will not take place, the latter expresses instead the impossibility of the same event. I will argue that only the first of these two meanings, the one with weaker truth-conditions (i.e. possible not) is problematic for five-year olds.

In the following section, I will introduce some basic notions of possi-ble-worlds semantics, illustrating how the distinction between strong and weak readings could be derived. In Section 3, some of the previous stud-ies on language development and modality will be presented. Against this background, in Section 4, I will present the results of two new experiments on the interpretation of Italian modals.

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2. STRENGTH-SCALE INVERSION IN NEGATIVE SENTENCES

In natural language semantics, modality has been traditionally analyzed with the machinery of possible worlds semantics (Kripke 1959; Hintikka 1957; see also Portner 2009 for a survey). In this framework, two key notions are relevant to our discussion: the accessibility relation and the force of the modal. The first notion, the accessibility relation, is required to define the kind of modality we are considering in evaluating the proposition. We may draw possible or necessary conclusions on the basis of the available evidence (episteMic modality), the set of normative rules in force (deontic modality), our desires (bouletic modality), and so on. The second notion, the force of the modal, captures instead the fact that different modals express a different degree of confidence in the truth of a proposition. To better illustrate, con-sider the sentences in (1) and (2) and their paraphrases in (3) and (4):

(1) John may be the culprit(2) John must pay for his crime(3) On the basis of my knowledge, in one possible world, John is the culprit(4) On the basis of the code of law, in every possible world, John pays for his crime

Sentences (1) and (2) are semantically equivalent to (3) and (4), mak-ing explicit the two aforementioned notions of accessibility and force. The first part of (3) and (4) illustrates the accessibility relation, defining the set of possible worlds taken into consideration. In (3) and (4) we are talking about two different sets of worlds: in (3) we are considering the worlds where what I know in the actual world is true, while in (4) we are consider-ing the worlds which share the same code of laws with this one. Thus epis-temic modality and deontic modality are distinguished by the fact that they define two different sets of possible worlds.

The second part of (3) and (4) – in one possible world/in every pos-sible world – captures instead the force of the modal: in (3) we are saying that the proposition is true if there exists one world where John is the cul-prit, while in (4) the preposition is true only if John will pay for his crime in every world. According to this view, we can distinguish the meaning of necessary and possible by saying that, given a set of worlds, the first is a universal quantifier while the second is an existential one.

The distinction between accessibility and force is useful to keep distinct two separate aspects of modal development. When we compare different kinds of modality i.e. epistemic vs. deontic, we are comparing the devel-opment of two separate accessibility relations. When we consider modals belonging to the same kind, we are instead comparing their force. Given that only epistemic modals will be considered here, it is this last aspect that I will explore in more detail.

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In addition to the distinction between accessibility and force, a third no-tion is operative when pairs of modal expressions are considered. This is the notion of strength, rooted in the neo-Gricean tradition (Gadzar 1979; Horn 1989). This notion is relevant here since it permits us to rank modal expressions along a scale. To illustrate this point, consider again sentence (1), repeated as (5), and compare it with the alternative in (6).

(5) John may be the culprit (6) John must be the culprit

Whenever (6) is true, (5) is also true. However, it is easy to verify that the inverse does not hold. Sentence (5) can be true but (6) false at the same time: the fact that John may be the culprit does not force us to believe that he must be the culprit. Thus, we could define strength in terms asymmetric entailment, and order modals in accordance to a scale in which the stronger expression asymmetrically entails the weaker one:

(7) necessity > possibility

This idea, more or less explicitly stated, has been central in many stud-ies on modal development (Hirst & Weil 1982; Byrnes & Duff 1989; Bas-celli & Barbieri 2002).

The problem is that the strength relation given in (7) is not absolute and it may vary once an additional logic operator is added to the sentence. Neg-ative sentences are a paradigmatic case. In fact, when a negative operator is inserted, the relation in (7) reverses. If negation takes wide scope over a pair of modal expressions, their relative strength is inverted and the entail-ment goes into the opposite direction:

(8) not necessary < not possible

It is easy to verify that a sentence like it is not possible that John is the culprit has more stringent truth conditions than the alternative it is not nec-essary that John is the culprit. In this sense, not possible asymmetrically entails not necessary.

To fully capture the complex ways negation and modality interact, the last distinction which has to be considered regards their logic scope. Nega-tion may combine with a modal in two different ways: either taking wide or narrow scope (for Italian, see Moscati 2010). With wide scope, negation is interpreted over the modal and the readings not possible and not neces-sary are derived. If negation takes instead narrow scope, the alternative in-terpretations possible not and necessary not are generated.

At this point, we have a more accurate picture. The four possible logi-cal interpretations, given by the combination of force and scope, can be or-dered in accordance to their strength:

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(9) strong weaka. not possible > c. possible notb. necessary not > d. not necessary

What (9) ultimately shows is that the configurations in (9a-b) should be kept distinct from (9c-d)and that the correct strength-relations could be obtained only if force and scope are considered together. In the rest of the paper, I will assume a distinction between strong and weak readings as in (9), putting forward the hypothesis that weak readings are more challenging than strong readings in language development.

3. PREVIOUS STUDIES ON MODALITY

In children’s spontaneous productions, modal verbs are already attested be-fore the third year (Kuczaj & Maratsos 1975; Shepherd 1982; Bliss 1988; Stromswold 1990; Wells 1979; Perkins 1983). At the same time, in languages such as Turkish or Korean, children also begin to produce evidential mor-phemes (Aksu-Koç 1988; Aksu-Koç & Slobin 1986; Choi 1995), a linguistic category arguably related to modality (see Palmer 1986). However, although children start to use modals and evidentials from early on, several studies have shown that production and comprehension do not develop at exactly the same pace. In fact, an adult-like semantic competence is attested only later, at around the age of five (Bassano et al. 1992; Aksu-Koç 1988; Papafragou at el. 2007), when children start to give consistent answers in comprehension tasks. It is at this stage that subtle semantic distinctions, such as the ones of force and strength, can be investigated.

A variety of experimental tasks has been employed to study children’s comprehension of modals. One of the most widely adopted is the Hidden Object Forced Choice Task (HOFCT), initially introduced in Hirst & Weil (1982). This experimental paradigm, used with some variations in many successive studies, consisted of a simple scenario in which an object was hidden either under a cup or under a box. The children’s task was to find the hidden object relying only on the verbal clues provided by two puppets, who indicated a different location each using a modal of different strength:

(10) a. The peanut must be under the cup b. The peanut may be under the box

Given the pair in (10), if children were aware that must is stronger than may, they were expected to look under the cup instead of the box. The re-sult was that, with modals in the indicative mood, children preferred the stronger statement already at age 3 and they consistently selected it at age five. A similar result has been documented in Byrnes & Duff (1989). They

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also reported that five-year-old children already selected the strongest al-ternative in 84% of the cases. Analogous findings with the HOFCT have been successively reported also in Noveck et al. (1996), and in Bascelli & Barbieri (2002) with Italian speaking children. Taken together, these results seem to indicate that, by the beginning of the fifth year, children are sensi-tive to the strength of the modals.

However, the picture is more complex than that and this apparent early proficiency has not been fully acknowledged in the aforementioned studies. In fact, things become more complicated once negative sentences come into play. In the same study, Byrnes & Duff (1989) reported that the choice be-tween a pair of positive modal sentences (has to/can) was easier than the choice between a pair of negative modal sentences (can’t/might not). In another study, Noveck (2001) observed several different combinations of modals and negation by adopting a version of the HOFCT based on truth-values. Among the different conditions, negative modal sentences were also presented and children’s performance in the 5 year olds’ group was still at chance. These results, taken at face value, might suggest that children know the semantics of modals but they have a hard time when negation is insert-ed. However, this cannot be the whole story. In fact, negative sentences are not always more difficult than positive ones. For example, in the experiment from Bascelli & Barbieri (2002), negative sentences do not pose additional difficulties and they appear to be even easier than positive ones.

Given that a general opposition positive/negative is not adequate to cor-rectly capture the available data, I want to propose a solution to this appar-ent puzzle based on the distinction between strong and weak meanings as in (9). Let me restate the fundamental idea: negative modal sentences can-not be classified as strong or weak considering only the force of the modal, given that their strength is determined by the compositional result of two distinct operators, negation and modality. Thus, when negation takes wide scope over possibility, the meaning is a strong one (not possible). Con-versely, if negation receives narrow scope (possible not), the sentence re-ceives a weak meaning.

This idea has been explored in the domain of deontic modality in Moscati (2008) and Gualmini & Moscati (2009). In these two studies, Ital-ian children were presented with several story contexts in which they heard a negative sentence with a modal verb. The sentences were all true given the story they just heard, and they were of two kinds, weak (11) or strong (12).

(11) Il contadino può non dare le carote all’ elefante the farmer poss. not give the carrots to.the elephant a. *it is not possible that the farmer gives carrots to the elephant *strong b. it is possible that the farmer does not give carrots to the elephant weak

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(12) Il pilota non può guidare la moto the pilot not poss. drive the motorbike a. it is not possible that the pilot drives the motorbike strong b. *it is possible that the pilot does not drive the motorbike *weak

Interestingly, five-year-old children had no difficulty in accepting the strong sentences in (12), while weak sentences as (11) were rejected in the majority of the cases. When children were asked to explain why they (in-correctly) reject the weak sentences, their comments were all consistent with the strong reading. This result can be readily captured in terms of in-formational strength. If the idea that strength in negative sentences is a key factor, we may expect that the same difficulties found with deontic modals carry over into the realm of epistemic modality. This idea will be tested in a new experiment, described next.

4. CHILDREN’S INTERPRETATION OF MODALS UNDER NEGATION IN ITALIAN

Modal paradigms vary across languages and different strategies can be adopted to disambiguate negative sentences. Some languages, such as Eng-lish, have a rich paradigm where different modal forms can be used to dis-tinguish between narrow and wide scope readings. The alternation between can and might is one example. Other languages instead have a more impov-erished modal paradigm and they need to resort to alternative disambiguation strategies. One of them, found in Italian, is word order. Italian has only two modals:1 potere ‘can’ and dovere ‘must’. These forms are free from polarity restrictions and their meaning in negative sentences is solely determined by their position with respect to negation. Consider the sentences in (13):

(13) a. Ci può non essere una mucca nella scatola there possible not be a cow in.the box ‘There might not be a cow in the box’ (weak: possible not) b. Non ci può essere una mucca nella scatola not there possible be a cow in.the box ‘There cannot be a cow in the box’ (strong: not possible)

In both sentences (13a-b) the same modal potere, inflected for person and number, is used. However, when the modal precedes negation (13a), it takes wide scope and the sentence expresses the meaning possible not.

1 Another quasi-modal is bisogna, with a meaning similar to need. This form has idiosyncratic properties which distinguish it from the other two modals potere and dovere. For example, in Standard Italian, it cannot have a referential subject.

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When instead the modal follows the negation (13b), the resulting interpreta-tion is the stronger not possible. This shows that in Italian the interpretation is determined by the surface order of the two elements.2 Given its extreme-ly simple modal paradigm, Italian is a profitable testing ground to observe children’s interpretation of negative modal sentences.

In Experiment 1 and 2, sentences such as (13a-b) will be tested in a reasoning scenario based on the hidden-object task. This procedure, com-bined with truth-value judgments, is similar to the one adopted in Noveck (2001).3 The first reason to use this protocol is that the truth-value of a sen-tence is a better predictor of children’s choices. In fact, when the context is manipulated in order to make only one sentence in the pair true, children consistently choose the true sentence, regardless of the relative force of the modal (Noveck et al. 1996). The second reason is that in the traditional HOFCT contradictory statements are generated. As an example, consider the pair in (14):

(14) a. The ball can be under the cup b. The ball must be under the box

In the original version of the task, sentences as in (14) were presented in absence of epistemic evidence and they could be both true. Given this state of affairs, a low performance could have been due to the confusion generated by two potentially true but contradictory sentences.

3.1 Experiment 1. Truth-value judgments in a reasoning scenario

In Experiment 1, only one sentence was presented at the time and its truth conditions had to be evaluated against a simple scenario, illustrated in Table 1. Children had to evaluate the target sentence against the content of a closed box (Box C) by drawing inferences on the basis of what they already knew about the content of two other open boxes (Box A and Box B). Children were told, in fact, that box C had the same content as either Box A or Box B.

ExpErimEntal SEtting

Outside Open Box A Open Box B Closed Box Cstrawberry horse + cow horse ? = A or B

table 1. reasoning scenario in experiMent 1.

2 In this sense, the logical and the syntactic representations are isomorphic, given that the Logical Form and the Phonological Form coincide.3 A difference from Noveck (2001) is the presence of an extra object (e.g. an apple). The extra object was added outside the boxes to counterbalance true and false answers.

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We used the given scenario to evaluate children’s interpretation of three different kinds of modal sentences: positive, negative weak, and negative strong. These conditions are illustrated in (15)-(17) and they were counter-balanced for true and false answers:

(15) Positive a. Ci può essere una mucca nella scatola True ‘There might be a cow in the box’ b. Ci può essere una fragola nella scatola False ‘There might be a strawberry in the box’(16) Negative strong a Non ci può essere una fragola nella scatola True ‘There cannot be a strawberry in the box’ b. Non ci può essere una mucca nella scatola False ‘There cannot be a cow in the box’(17) Negative weak a. Ci può non essere una mucca nella scatola True ‘There might not be a cow in the box’ b. Ci può non essere un cavallo nella scatola False ‘There might not be a horse in the box’

Consider these sentences in relation to the content of box C. According to the experimental set up, box C contained either a cow or a cow and a horse. The extra object (strawberry) was positioned outside the boxes, so it could not be contained in box C. Given this state of affairs, sentence (15a) is true, given that in box A there was actually a cow. By contrast, sentence (15b) was clearly false, because the strawberry was neither in box A nor in box B.

In the second pair of sentences, the modal is contained in a negative statement. In (16) the modal potere follows the negative marker non and, here, the only interpretation is the strong not possible one. Under this inter-pretation, the assertion in (16a) that there cannot be a strawberry was true, whereas the assertion in (16b) that there cannot be a cow, was false.

In the last pair, the order between negation and the modal is reversed and in (17) the modal precedes the negative marker. The only reading al-lowed in adult grammar is the weak interpretation possible not. Under this meaning, (17a) was true, since a cow was not necessarily in box C, while (17b) is false since box C had to contain a horse, either alone (box A) or with a cow (box B).

In Experiment 1, we tested children in the three different conditions, where the conditions negatiVe weak and negatiVe strong only differ in the position of negation. The prediction is that, if children have difficulties with weak meanings, a difference in the rate of correct answers should be ob-servable between these two conditions.

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Participants: twenty monolingual Italian-speaking children took part in the experiment, recruited from kindergartens in the cities of Siena and Florence. The age range was between 5;1 and 5;11 (M=5;4). A group of 18 adults served as a control group.

Materials: the experimental material included eighteen white cardboard boxes, divided into six sets and displayed on a table in front of the partici-pants. Different objects were placed inside the boxes (animals, fruit, small toys) and a hand puppet was used to present the sentences.

Method: we tested subjects’ interpretations using the Truth Value Judg-ment Task methodology (TVJT) (Crain & Thornton 1998) and setting up a game scenario (as in Table 1) with small toys and boxes. A series of statements were uttered by a friendly puppet and the participants’ role was to determine whether the puppet was “right” or “wrong” on the basis of the items placed within the cardboard boxes. Children rewarded the pup-pet with a prize every time they thought it said something right, while they gave it a neutral object when they thought it was wrong.

The test phase was preceded by a familiarization procedure in two stages. The first stage consisted in a naming task combined with TVJs: the experimenter pointed at several objects within the open boxes and asked the puppet to say what was in the box. The puppet then uttered a simple declarative sentence of the form this is an X and the participants had to decide whether the puppet was right or wrong. When it was wrong, they had to correct it by saying the real name of the object. This preliminary task served to familiarize children with the TVJT and to verify that they all knew the name of the objects used later in the test session.

The second part of the training was more similar to the following test procedure. Children had to judge sentences about the closed box (box C), whose content was inferable given a simple rule. The rule was that the content of box C was exactly the same as the content of one of the two open boxes (box A, box B). At this stage, children were familiarized with the inferential rule and they were allowed to look into the closed box be-fore judging the puppet’s statement. Children were told that “the closed box has the same content as one of the two open boxes. It contains either what is in this box (a) or what is in this box (b)”. The experimenter pointed at the boxes in turn and named every single object in the scenario. She also told the children that the object outside the boxes (i.e. a strawberry) was “never in the closed box”. Crucially, before deciding whether the puppet’s statement was right or wrong, this time children were allowed to peep in-side box C. In this way, children got an immediate feedback on the possible content of the closed box. At this stage, children saw two sets of boxes. In the first set, the content of box C was similar to box B (i.e a single animal, as in Table 1); while in the second set it was similar to box A (i.e. two

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animals, as in Table 1).4 The puppet uttered a declarative sentence of the form there is/isn’t a(n) X in the box and the participants had to judge his statement. For each of the two sets of boxes, children had to judge three sentences.

At the end of the familiarization procedure, children still had four sets of boxes in front of them. Now statements with modal were introduced. Six sentences were presented for each set of boxes, two for each experimen-tal condition, as in (15)-(17). Six different presentation lists were prepared and subjects were randomly assigned to one of them. Every subject heard 8 sentences per condition, 4 true and 4 false, for a total of 24 sentences. Eve-ry time a sentence was judged “wrong”, the subject was asked to provide a brief comment.

Results: responses were considered successful whenever the participant accepted the true sentences and rejected the false ones, in accordance with the presentation setup. In the case of “wrong” answers, children had to say why the puppet was wrong. In the case that the answer was inconsistent with the reasoning scenario, it was excluded from the overall result (i.e. “wrong, because cows do not like boxes”). Table 2 reports the overall re-sults per group and condition.

group ConditionS

Positive Negative Strong Negative Weak

T F tot T F tot T F Tot

Children 0.53(42/79)

0.94(75/80)

0.73(117/159)

0.64(50/78)

0.75(60/80)

0.69(110/158)

0.38(30/78)

0.67(53/79)

0.53(83/157)

Adults 1.00(72/72)

1.00(72/72)

1.00(144/144)

0.79(57/72)

1.00(72/72)

0.90(129/144)

0.94(68/72)

0.93(67/72)

0.94(135/144)

table 2. proportion of correct answers in the three conditions for each truth-Value.

Let us first consider the answers given by the adults. The 18 partici-pants correctly evaluated the positive sentences, while negative sentences were only slightly more problematic, with a general performance above 90%. Notice that answers in the weak negative condition (94%) were not any less accurate than in the strong negative one (90%).

The result concerning children’s performance in general was notably lower: they provided the right answer in the positive condition in only 73%

4 This feedback excludes the possibility that children could misinterpret the rule in accordance to the meaning “C contains what is in box A and what is in box B”. Under this interpretation, only the presence of three animals would have been allowed in box C. However, the actual content of the closed box was inconsistent with this last interpretation. For the same reason, and to favor the exclusive-OR interpretation, the rule was also stated using the partitive expression one of the two boxes.

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of the cases and their proportion of correct judgments decreased in the neg-ative strong (69%) and in the negative weak (53%) conditions. Notice that the performance in this latter condition is extremely poor, when compared with the 94% of correct answers of the adults. A comparison between the proportion of correct answers in the two groups is reported in Figure 1.

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figure 1. proportion of correct answers.

Data were submitted to a 2 × 3 ANOVA, with Age as a between-subject factor (adult, children) and Condition (positive, negative weak, negative strong) as a within-subject factor. The proportion of correct answers was transformed with an arcosin function and encoded as the dependent vari-able. The analysis showed a significant main effect of Condition (F (2, 36) = 7.064, p<0.005) and Age (F (1, 36) = 90.851, p<0.001). The interaction between Age × Condition was also significant (F (2, 36)=3.352, p<0.05), confirming that the understanding of modal sentences increases with age.

Since we are primarily interested in comparing children’s and adult’s performance in the different conditions, a series of post-hoc comparisons was run using Bonferroni correction.

In the negative strong condition, no significant difference was found between adults and children. The difference between the two groups was instead significant in the negative weak condition (p<0.05), confirming that not all negative modal sentences are equally problematic for five-year-old children.

The post-hoc analysis also revealed a significant contrast in the positive condition (p<0.05). This result is quite surprising and deserves a closer ex-amination. First, let us consider children’s answers in the positive condition

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for true and false sentences separately. By inspecting the data, it turns out that children’s mistakes are largely confined to true positive sentences as (15a), where the proportion of correct answers drops to a low 53%. For the ease of the reader, (15a) is repeated in (18) below:

(18) Ci può essere una mucca nella scatola ‘There might be a cow in the box’

Taken at face value, the high rate of rejections is compatible with the hypothesis that children confuse potere/might with dovere/must. Under this view, children would have difficulties with modals even in positive sen-tences, incorrectly rejecting (18). However, this kind of explanation does not seem to be consistent with the motivations given by the children. Remember that whenever the puppet’s sentence was judged “wrong”, we asked the sub-jects to say why they thought the sentence was inappropriate. Now, when we requested them to justify their rejections of (18), many of the children commented that the sentence was false “because there is also a horse in the box”. The problem is that, if children interpret (18) as “there must be a cow in the box” the great majority of their comments become inconsistent:

(19) Puppet: There must be a cow in the box Children: False. #There is also a horse in the box

This encourages us to explore a second alternative. As just said, chil-dren often used the expressions also in many of their comments. This was a useful hint, given that this particle is related with focus (Krifka 2007) and it is often used to deny an assertion of exhaustivity, as the one associated with only in (20).

(20) Every other x, where x ≠ cow, is not in the box

Now, (20) is clearly false in the context, given that a horse must also be in the box. According to this view, children correctly interpret the modal in (18), but they focus the nominal constituent the cow: a reading equiva-lent to “only a cow”. When children’s comments are considered, this sec-ond line of reasoning seems to be on the right track, as the perfectly natural exchange below shows:

(21) Puppet: There might be only a cow in the box Children: False. There is also a horse in the box

Under this account, children know the meaning of potere/may but they reject the sentences by virtue of a focused interpretation. The prediction is that, if the assertion in (20) is made true in the context, children will accept the positive modal sentences at a higher rate. This issue will be directly ad-dressed in Experiment 2.

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Discussion: Experiment 1 shows that certain modal statements are still problematic for five-year-olds and that children’s mistakes are qualitatively and quantitatively different in the various conditions. The lowest perfor-mance was found in the negative weak condition, in accordance with the prediction that weak readings are the most problematic ones. If compared with the good performance found with strong negative sentences, this re-sult confirms that children do not have problems with negative sentences in general, but only with sentences in which the interaction between the mod-al and negation originates a weak interpretation.

Apart from weak negative sentences, the other interesting asymmetry between adults and children regards positive sentences. This difference is likely to be unrelated to modality, as suggested by children’s comments. It seems more plausible to assume that a pragmatic factor associated with fo-cus is at play here. The question is whether the effect of this assertion of exhaustivity can be put in relation with children’s rejections of weak nega-tive sentences. Let me briefly discuss this point, by assuming, for the mo-ment, that weak negative sentences as (17a) are also enriched by an asser-tion of exhaustivity similar to the one introduced by only. Following this reasoning, children would interpret (17a) as in (22) below:

(22) There might not be only one cow in the box True

According to this interpretation, however, the sentence would still be true, given that there actually was a horse in the closed box. This would not then explain why children reject true negative weak sentences. On the contrary, if children assign the wrong inverse logic scope to the sentence in (17a) and derive a non-target strong reading as in (23).

(23) There cannot be one cow in the box False

Their rejections will follow straightforwardly, given that (23) was false in the context. Moreover, this reading was also consistent with children’s explanations. In fact, most of the time children explained/justified their re-jections by saying that the sentence was false because “a cow may be in the box”.

Let me take stock and summarize here the results of Experiment 1. The main result is a significant difference between adults and children, due to a lower performance of the five-year-olds in the positive and in the weak negative condition. What is interesting for our hypothesis is the fact that a sharp asymmetry between the negative strong and the negative weak sen-tences emerges, confirming that these two constructions pose different chal-lenges for young language learners. A residual question concerns the high rate of rejections found in the positive condition. Children’s explanations

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of their rejections suggests that an extra factor, related with focus, might be at play here. If this idea is on the right track, we should be able to disen-tangle the effect of focus from the one of strength. In a second experiment, a contextual manipulation was introduced in order to cancel the effect of focus. We then expect a steady increase in the acceptance rate for positive sentences. On the contrary, no improvement should be observable in nega-tive weak sentences.

3.2 Experiment 2. Covert only and the assertion exhaustivity

In Experiment 1, the overall pattern of results indicates that children have a tendency to reject true sentences. However, different types of sentences could have been rejected for different reasons: positive sentences could have been rejected because children enrich their meaning with a salient assertion, weak negative sentences could have been instead rejected because children misin-terpret them in accordance with the wrong scope assignment. If this idea is on the right track, we should be able to distinguish between the two differ-ent factors. This can be done by manipulating the context to make sure that the sentences will be true even if an assertion of exhaustivity is generated. In this way, children’s difficulties should be only confined to negative weak sentences.

Remember that in Experiment 1 a toy was placed in both the open boxes, for example the horse in the scenario given in Table 1. In this setting, the horse is obligatorily present in the closed box, with or without the other toy-animal. The other toy (the cow, in Table 1), instead, could not stand by itself within box C. This state of affairs makes the positive modal sentences false if focus is assigned to the nominal constituent, resulting in a reading equivalent to “there might be only a cow in the box”. In order to nullify the effect of focus, we resorted to a simple contextual manipulation. The new experimental set-up is given in Table 3. Now, two different toys appear in each open box, a horse in one box and a cow in the other. The closed box therefore contains only one or the other of these animals. An additional set of animal-toys is left outside the boxes in order to counterbalance true and false sentences.

ExpErimEntal SEtting

Outside Open Box A Open Box B Closed Box Cduck, rooster, pig, goat cow horse ? = A or B

table 3. reasoning scenario in experiMent 2.

In the slightly modified scenario, the assertion of exhaustivity does not affect the truth conditions of the sentences, as (24a-b) and (25a-b) show:

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(24) Ci può essere una mucca nella scatola a. There might be only a cow in the box True b. There might be a cow in the box True(25) Ci può non essere una mucca nella scatola a. There might not be only a cow in the box True b. There might not be a cow in the box True

The positive sentence in (24) is true, regardless of whether an assertion of exhaustivity is generated or not. The same also holds for sentence (25), which is true if children have access to the weak reading possible not. How-ever, according to our experimental hypothesis, this reading is harder to ac-cess and children’s rejections would be independent from focus assignment. We expect that children would still judge sentence (25) as wrong.

In Experiment 2 we tested again the three kinds of sentences used in Ex-periment 1. This time, all the test sentences were true in the given context:

(26) Positive Può esserci una mucca nella scatola ‘There might be a cow in the box’ True(27) Negative Strong Non può esserci un’oca nella scatola ‘There cannot be a duck in the box’ True(28) Negative weak Può non esserci un cavallo nella scatola ‘There might not be a horse in the box’ True

Remember that all the sentences in (26)-(28) are unambiguous in adult Italian and they are all true in the scenario illustrated in Table 3.

As a control, for each set of boxes, we also presented three other posi-tive sentences referring to the toys outside of the boxes as in (29), which were all false in the given context. This allowed us to balance true and false sentences:

(29) Può esserci un gallo nella scatola ‘There might be a rooster in the box’ False

Participants: eighteen monolingual Italian-speaking children from 5;2 to 6;1 (mean 5;5) participated to the experiment. An additional group of 10 adults served as a control.

Materials: the experimental material included twenty-one white card-board boxes, grouped into seven sets. As in Experiment 1, the boxes were all displayed on a table in front of the participants.

Method: the experimental procedure was analogous to the one adopted

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in Experiment 1, with the same two-stage familiarization procedure preced-ing the test.

During the test phase, children were presented with five sets of boxes and, in each set, two boxes were open and one was closed. Outside of the boxes, four other animals were placed. Six sentences were presented for each set of boxes: one sentence for each experimental condition plus three fillers as in (29). In total, children and adults heard 30 sentences in the test phase. Again, children rewarded the puppet if they thought it was right. When they instead thought it was wrong, they were asked to explain why.

Results: once the confound associated with focus was eliminated, re-sults appeared to be quite sharp. Adults did not have any trouble in judg-ing sentences in (26)-(28) and they accepted all the test sentences, indicat-in (26)-(28) and they accepted all the test sentences, indicat-ing that the adults were also facilitated from the contextual manipulation introduced in Experiment 2. Things are instead quite different for children. In this modified scenario, children’s performance dramatically increased in the positive condition, being already at almost the same level as adults. In the negative weak condition, instead, the experimental manipulation did not produce any relevant effect: in Experiment 1 the acceptance rate of true negative sentences was at 38% and it was also attested at around the same level (33%) in Experiment 2. The overall results are reported in Table 4.

group ConditionS

Positive Negative Strong Negative WeakChildren 0.96

(86/90)0.87

(78/90)0.33

(30/90)Adults 1.00

(50/50)1.00

(50/50)1.00

(50/50)

table 4. proportion of correct answers.

The proportion of correct responses was transformed with the arccosine function and a 2 (Age: adult, children) × 3 (Condition: positive, negative weak, negative strong) ANOVA was conducted. This analysis showed a sig-nificant main effect of Condition (F (2, 26) = 13.607, p<0.001) and Age (F (1, 36) = 112.207, p<0.001). The interaction between Age × Condition was also significant (F (2, 52)= 13.607, p<0.05).

Again, we ran a series of post-hoc comparisons with Bonferroni correc-tion, in order to assess the effect of each experimental condition on the pro-portion of correct responses. The only significant contrasts were the ones between the weak negative conditions and the other two (p<0.001), a result in line with our experimental hypothesis.

Regarding the answers to the control sentences, Table 5 shows that both the children and the adult groups gave an extremely high proportion of correct answers, with children’s performance being already at adult level.

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figure 2. acceptance rate of true stateMents in the three experiMental conditions.

group rate of correct rejections

Children 0.98(267/270)

Adults 1.00(150/150)

table 5. proportion of correct answers/rejections to controls.

Discussion: in Experiment 2, the reasoning scenario was slightly modi-n Experiment 2, the reasoning scenario was slightly modi-fied with respect to the previous experiment: this time only one animal was placed within each open box. As a consequence of this manoeuvre, the pro-portion of deviant answers in the positive condition dramatically decreased. Notice that this result cannot be accounted for by assuming that children misinterpret might as must given that, under this account, children would have continued to reject positive statements, contrary to facts.

This second experiment also excludes another possible explanation, based on a pragmatic violation. One reviewer suggested that weak negative sentences could have been rejected because they would violate the conversational principles based on scalar implicatures. In fact, if children add a covert only, both sentences (30) and (31) become true:

(30) There might not be only a cow in the box(31) There must not be only a cow in the box

Given that the stronger statement, the one with must in (31) is also true, the assertion of (30) would be infelicitous, in violation of conversational

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rules (the Maxim of Quantity, Grice 1975). Under this account, weak sentences would be rejected for reasons of discourse-pragmatic.

This line of reasoning can be excluded now, when we consider the results from Experiment 2. In the revised scenario, a cow alone can be in the closed box. Now sentence (31) is false, and no pragmatic violation arises. Under the pragmatic account, we would have expected a higher acceptance of (30) in Experiment 2 than in Experiment 1. However, this was not the case and the manipulation of the scenario had no effect on the acceptance rate of the weak negative sentences (see Moscati 2011 for a discussion on other types of discoursive factors). Results in the negative conditions are instead consistent between the two experiments, as predicted by an account based on the relative strength of the modal sentences.

5. GENERAL DISCUSSION

Broadly speaking, the category of epistemic modality allows the speaker to modulate his degree of confidence about a proposition. This intuition played a central role in many of the previous studies on language development, and sentences with modals have often been compared in relation to their strength. However, the notion of strength was not fully explored, especially in those cases where two (or more) logic operators interact. When negation is entered into the equation, for example, we saw that the strength relations are actually reversed, at least when negation takes wide scope: although necessary is stronger than possible, in negative sentences not necessary becomes weaker than not possible. On the basis of these considerations, we can isolate a family of weak negative readings. For the ease of the reader, the entailment relations presented in (9) are repeated again in (32) below:

(32) strong weaka. not possible > c. possible notb. necessary not > d. not necessary

The goal of this paper was to show that the weak readings could be delayed with respect to the strong ones, at least in Italian, a language with an extremely simple modal paradigm. The results of Experiment 1 and 2 show that children do not have problems in negative sentences tout court, but only with weak negative ones. This explains some of the results reported in the previous studies on modal comprehension. As an example, the sentences from (33) to (35) have been listed among the most difficult to process:

(33) It might not be under the blue cup (Byrnes & Duff 1989) (34) There might not be a bear (Noveck 2001) (35) There does not have to be a bear (Noveck et al. 1996)

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Now, to the extent that our results on Italian are generalizable to other languages, the complexity posed by (33), (34) and (35) ceases to be unex-pected, given that they all belong to the same family of weak readings.

A further question is why weak readings should be disadvantaged with respect to strong ones? What we have observed here is the fact that chil-dren cannot differentiate between the weak reading possible not and the strong one not possible. In terms of the Operating Principles proposed in Slobin (1985), it seems that children at age five are not able to apply the principle of unifunctionality and to assign two different meanings to the two different word orders. Notice, however, that children’s mistakes are unidirectional: the weak reading (32c) is interpreted in accordance with the strong reading (32a), but not vice versa. How could we explain that? By looking at the other Operating Principles, the one ruling the interpre-tation of operators (position: operators) would make the right prediction, assigning the widest possible scope to negation, favoring the reading in (32a). However, this solution faces some empirical problems. In Moscati & Gualmini (2008), Italian children’s interpretations of (32d) were tested in sentences such as the farmer needs not to feed the animals. Now, if an Operating Principle assigns the widest possible scope to negation, this read-ing of (32d) should be perfectly acceptable. However, Moscati & Gualmini found a very low acceptance rate. Notice that this result is instead compat-ible with the hypothesis that weak meanings are disfavored in early gram-mar. Moreover, the idea that negation always takes the widest scope is also problematic once nominal quantifiers are considered. In the case of univer-sal nominal quantifiers, for example, Musolino (1998) and Musolino et al. (2000) showed that in sentences where eVery c-commands negation, as in every horse didn’t jump over the fence, negation does not take wide scope and children have no problem in accessing the adult reading, the one in which negation takes narrow scope under the quantifier.

In order to explain children’s preference for (32a), I would like to in-dicate two possible directions. A first possibility is that the processing of weak readings requires more computational resources as compared with the processing of strong readings. As a result, their processing is expected to be generally harder. Under this account, we might expect that even adults, pro-vided with a sufficiently demanding task, should encounter certain difficul-ties with weak negative sentences. A second possibility is, instead, that the special status of weak readings is confined to the early stages of language development and that this kind of interpretation is delayed for reasons of learnability. Let me briefly discuss these two alternatives in turn.

The fact that the processing of negation has a cognitive cost is well-

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known (Wason 1965)5 and it can be shown that this cost increases in the case of the weak meanings. Under standard assumptions of composition-ality, a possible computation of strong readings will unfold stepwise. The event structure, the modal base, the quantificational force and the negative operator will be processed in turn. I will assume that a sentence like the cow cannot be in the box has the following logic representation and that the computation moves from the core event structure (1) to the other logic op-erators in the higher clausal positions (2,3,4):

(36) [4not [3exist a world [2on the basis of the present knowledge where [1inside (cow, box)]]]]

The representation in (36) corresponds to the strong reading not possible, where negation takes wide logic scope over the modal. The first operation is to create the event structure, then the modal is interpreted (step 2 and 3) and last, the negative operator is added. I will sketch a possible computation below:

Step 1. Event structure: the representation inside(cow, box) is created.Step 2. Accessibility relation: the relation, established on the basis of our

knowledge between the actual world and the set of conceivable possible worlds, denotes the set W of worlds where the relation inside(cow, box) is validated.

Step 3. The (existential) quantifier insures that this set is not empty: W≠0Step 4. Negation inverts the truth-value: W=0

Crucial to our discussion is step 2. Here, only the set of possible worlds where a cow is within the box is taken into consideration: alternative event structures (e.g. worlds where a horse or a crocodile are inside the box) are not examined.

Consider now the case of weak readings. In the case of the possible not readings, negation has narrow scope and enters into the computation at a different stage, preceding the modal:

(37) [4exist a world [3on the basis of the present knowledge where [2not [1inside (cow, box)]]]]

5 Negative sentences require computing and accommodating a certain number of presuppositions. A way to capture this idea is by assuming that every negative sentence forces one to consider its positive counterpart. The more salient the positive sentence is, the faster the processing of negation. In accordance with this idea, the processing of a simple sentence like it is not green requires one to consider first it is green. If this last sentence is made salient in the context, then the presuppositions are naturally accommodated, facilitating the sentence processing.

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According to (37), negation is interpreted immediately after the event structure, deriving the narrow scope reading. Again, for clarity, I report the steps below:

Step 1. Event structure: the representation inside(cow, box) is created.Step 2. Negation is applied: alternative events are taken into consideration

(the box is empty, a horse is in the box, a crocodile is in the box …)Step 3. Accessibility relation: the relation, established on the basis of our

knowledge between the actual world and the set of conceivable possible worlds, denotes the set W of worlds where the relation not inside(cow, box) is validated.

Step 4. The (existential) quantifier ensures that this set is not empty: W≠0

Notice that, if negation is computed after the event structure, a wider array of possible events has to be considered (e.g. worlds where a horse or a crocodile are inside the box): negation has the effect of enlarging the set of worlds under consideration. Under this account, weak readings require extra cognitive resources both for adults and children. However, these resources might not be fully available to children at this stage. Thus, children may opt for the less demanding reading and interpret the sentences in accordance with the stronger meaning.

An alternative explanation is that the computational demands for weak and strong readings are the same and that strong readings are considered first by virtue of a learnability bias, active on the early stages of language development. This mechanism has been proposed to solve the particular learnability problem described in Crain et al. (1994). According to these authors, a problem arises whenever a sentence can be mapped onto two different interpretations and one of them asymmetrically entails the other. This is exactly the situation we are dealing with. To illustrate, I will use the English sentences in (38) and (39), underscoring that the same argument directly extends, mutatis mutandis, to Italian. Consider the sentence in (38) and its potential ambiguity, for a young learner, between the two meanings below:

(38) The cow may not be in the box a. *it is not possible that the cow is in the box strong b. it is possible that the cow is not in the box weak

If the child incorrectly assigns the meaning (38a) to (38), it will be relatively easy for him/her to recover from this initial mistake: once he/she sees that a cow is actually in the box, he/she will understand that this interpretation is too restrictive. As a result, he/she will immediately switch to the weak reading in (38b). Thus, it is quite easy to escape from a wrong interpretation by starting from the strongest meaning.

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Now consider sentence (39) and let us assume, for the sake of the argument, that children mistakenly interpret it in accordance to the weak reading in (39b):

(39) The cow can not be in the box a. it is not possible that the cow is in the box strong b. *it is possible that the cow is not in the box weak

If this happens, there is no positive logical evidence showing them that this reading is incorrect, given that (39b) is true either when a cow is in the box or when a cow is not in the box. Following this argument, there seems to be a clear advantage, in terms of learnability, in hypothesizing the strong meanings first (see Crain et al. 1994) for a formulation of this principle in terms of subset/superset).6 Our results could then be explained by assuming that the interpretations in (38a)-(39a)will be attempted first and, in case, revisited in favor of the weaker ones (38b)-(39b)on the basis of the growing evidence available to the child.

A remaining question concerns the distribution of the covert only. We observed that children associate it with a constituent in positive sentences, and that they do not do so in negative sentences. A tentative explanation would be to also relate this fact to the notion of strength: only is associated with a constituent solely if a stronger statement is generated. In positive sentences, the insertion of only makes (41) stronger than (40), assigning to the sentence more stringent truth conditions (i.e. (41) but not (40) is false when a cow and a horse are together in the box).

(40) It is possible that a cow is in the box(41) It is possible that only a cow is in the box

Under negation, however, a covert focus operator would have the op-posite effect, weakening the sentence. In this case (43) and (45) are true in a situation (again, when a cow and a horse are together in the box) where their non-focused counterparts in (42) and (44) are instead false:

(42) It is not possible that there is a cow in the box(43) It is not possible that there is only a cow in the box(44) It is possible that there is not a cow in the box(45) It is possible that there is not only a cow in the box

6 Other kinds of empirical evidence, such as the computation of conversational implicatures (Gualmini & Schwartz 2009) could be used to overcome the problem posed by sentences of the sort of (39). See also Guasti et al. (2005) on the development of scalar implicatures. In any case, additional assumptions would be required to account for the preference for strong readings at this stage of development.

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In conclusion, when the facts about the covert only are considered, an account based on strengthening and learnability as in Crain et al. (1994) seems to better capture this additional pattern, explaining with a single mechanism both types of incorrect rejections found in Experiment 1.

REFERENCES

Aksu-Koç, A. (1988). The acquisition of aspect and modality: The case of past ref-erence in Turkish. Cambridge: Cambridge University Press.

Aksu-Koç, A. & D. Slobin (1986). A psychological account of the development and use of evidentials in Turkish. In W. Chafe & J. Nichols (eds.), Evidential-ity: The linguistic coding of epistemology, 159–167. Norwood, NJ: Ablex.

Bliss, L. S. (1988). Modal usage by pre-school children. Journal of Applied Devel-opmental Psychology 9. 253–261.

Bascelli, E. & M. S. Barbieri (2002). Italian children’s understanding of epistem-ic and deontic modal verbs dovere (must) and potere (may). Journal of Child Language 29. 87–107.

Bassano, D., M. Hickmann & C. Champaud (1992). Epistemic modality in French children’s discourse: ‘to be sure’ or ‘not to be sure’? Journal of Child Lan-guage 19. 389–413.

Byrnes, J. P. & M. A. Duff (1989). Young children’s comprehension of modal ex-pressions. Cognitive Development 4. 369–387.

Choi, S. (1995). The development of epistemic sentence-ending modal forms and functions in Korean children. In J. Bybee & S. Fleischman (eds.), Modality in grammar and discourse, 165–204. Amsterdam & Philadelphia: John Ben-jamins.

Crain, S., W. Ni & L. Conway (1994). Learning, parsing, and modularity. In C. Clifton, L. Frazier & K. Rayner (eds.), Perspectives on sentence processing, 443–467. Hillsdale, NJ: Erlbaum.

Crain, S. & R. Thornton (1998). Investigations in Universal Grammar: A guide to experiments on the acquisition of syntax and semantics. Cambridge, MA: The MIT Press.

Gazdar, G. (1979). Pragmatics: Implicature, presupposition and logical form. New York: Academic Press.

Grice, H. P. (1975). Logic and conversation. In P. Cole & J. Morgan (eds.), Syntax and semantics. Volume 3: Speech acts, 41-58. New York: Academic Press.

Gualmini, A. & V. Moscati (2009). The early steps of modal and negation interac-tions: Evidence from child Italian. In E. Aboh, E. van der Linden, J. Quer & P. Sleeman (eds.), Romance languages and linguistic theory 2007, 131–144. Am-sterdam & Philadelphia: John Benjamins.

Gualmini, A. & B. Schwarz (2009). Solving learnability problems in the acquisi-tion of semantics. Journal of Semantics 26(2). 185–215.

Guasti, M. T., G. Chierchia, S. Crain, F. Foppolo, A. Gualmini & L. Meroni (2005). Why children and adults sometimes (but not always) compute implica-

247


tures. Language and Cognitive Processes 20. 667–696.Hintikka, J. (1969). Models for modalities. Dordrecht: Reidel.Hirst, W. & J. Weil (1982). Acquisition of epistemic and deontic meaning of

modals. Journal of Child Language 9. 659–666.Horn, L. R. (1989). A natural history of negation. Chicago: The University of Chi-

cago Press.Kuczaj, S. A. & M. P. Maratsos (1975). What children can say before they will.

Merrill-Palmer Quarterly 21. 89–111.Krifka, M. (2007). Basic notions of informational structure. In C. Fery & M. Krif-

ka (eds.), Interdisciplinary studies on information structure 6, 13–56. Potsdam: Universitätsverlag.

Kripke, S. (1959). A completeness theorem in modal logic. The Journal of Sym-bolic Logic 24(1). 1–14.

Lyons, J. (1977). Semantics. Cambridge: Cambridge University Press.Moscati, V. (2008). Strength and weakness of children’s interpretation of modals.

In Y. Otsu (ed.), Proceedings of the 9th Tokyo Conference on Psycholinguis-tics, 103–119. Tokyo: Hituzi Syobo.

Moscati, V. (2010). Negative raising: Logical form and linguistic variation. Cam-bridge: Cambridge Scholars Publishing.

Moscati, V. (2011). Discourse under control in ambiguous sentences. In J. Meibau-er & M. Steinbach (eds.) Experimental pragmatics and semantics, 63–78. Am-63–78. Am- Am-sterdam & Philadelphia: John Benjamins.

Moscati V. & A. Gualmini (2008). More facts that isomorphism cannot explain. In T. Friedman & M. Gibson (eds.), Proceedings of SALT XVII, 202–209. Ithaca, NY: CLC Publications.

Musolino, J. (1998). Universal Grammar and the acquisition of semantic knowl-edge. University of Maryland at College Park dissertation.

Musolino, J., S. Crain & R. Thornton (2000). Navigating negative quantificational space. Linguistics 38(1). 1–32.

Noveck, I. A. (2001). When children are more logical than adults: Experimental investigations of scalar implicature. Cognition 78(2). 165–188.

Noveck, I. A., S. Ho & M. Sera (1996). Children’s understanding of epistemic modals. Journal of Child Language 23(3). 621–643.

Palmer, F. (1986). Mood and modality. Cambridge: Cambridge University Press.Papafragou, A., P. Li, Y. Choi & C. Han (2007). Evidentiality in language and cog-

nition. Cognition 103. 253–299.Perkins, M. (1983). Modal expressions in English. London: Frances Pinter.Piéraut-Le Bonniec, G. (1980). The development of modal reasoning. Genesis of

necessity and possibility notions. New York: Academic Press.Portner, P. (2009). Modality. New York: Oxford University Press.Shepherd, S. C. (1982). From deontic to epistemic: An analysis of modals in the

history of English, creoles, and language acquisition. In A. Ahlquist (ed.), Pa-pers from the fifth international conference on historical linguistics, 316–323. Amsterdam & Philadelphia: John Benjamins.

Slobin, D. J. (1985). The crosslinguistic study of language acquisition: Theoretical

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VINCENZO MOSCATI

issues. Vol. 2. London: Erlbaum.Stromswold, K. (1990). Learnability and the acquisition of auxiliaries. Cambridge,

MA: MIT dissertation.Wason, P. C. (1965). The contexts of plausible denial. Journal of Verbal Learning

& Verbal Behavior 4(1). 7–11.Wells, G. (1979). Learning and using the auxiliary verb in English. In V. Lee (ed.),

Cognitive development: Language and thinking from birth to adolescence, 250–270. London: Croom Helm.

Vincenzo MoscatiMacquarie University – ARC Centre of Excellence in Cognition and its DisordersAustralian Hearing Hub, Macquarie University2109 North Ryde, NSWAustralia.e-mail: [email protected]

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