The interpretation of disjunction in Universal Grammar

LANGUAGE AND SPEECH, 2008, 51 (1 & 2), 151 S. –Crain 169

151

The Interpretation of Disjunction in Universal Grammar Stephen Crain Macquarie Centre for Cognitive Science

Key words

Abstract

child language

Child and adult speakers of English have different ideas of what ‘or’ means in ordinary statements of the form ‘A or B’. Even more far-reaching differences between children and adults are found in other languages. This tells us that young children do not learn what ‘or’ means by watching how adults use ‘or’. An alternative is to suppose that children draw upon a priori knowledge of the meaning of ‘or’. This conclusion is reinforced by the observation that all languages adopt the same meaning of ‘or’ in certain structures. For example, statements of the form ‘not S[A or B]’ have the same meanings in all languages, and disjunctive statements receive a uniform interpretation in sentences that contain certain focus expressions, such as English ‘only’. These observations are relevant for the long-standing “nature versus nurture” controversy. A linguistic property that (a) emerges in child language without decisive evidence from experience, and (b) is common to all human languages, is a likely candidate for innate specification. Experience matters, of course. As child speakers grow up, they eventually learn to use ‘or’ in the same way as adults do. But, based on findings from child language and cross-linguistic research, it looks like certain aspects of language, including the interpretation of disjunction, are part of the human genome.

cross-linguistic variation disjunction entailments focus expressions logical reasoning positive and negative polarity principles and parameters Universal Grammar

1Introduction Many facts about language remain hidden from learners, yet every learner figures them out, often very early in the course of language development. Advocates of universal grammar propose that young children solve some of these mysteries by drawing upon a priori knowledge of linguistic principles. This paper discusses a set of mysteries surrounding children’s emerging knowledge of the interpretation of disjunction in natural language (e.g., English ‘or’, Chinese ‘huozhe’, Japanese ‘ka’). Most of the input to children is consistent with an “exclusive-or” reading of

Acknowledgments: Several friends and colleagues provided helpful discussion of the issues raised in this paper: Brian Byrne, Gennaro Chierchia, Max Coltheart, Jean Hsu, Takuya Goro, Andrea Gualmini, Teresa Guasti, Chunyuan Jing, Thomas Lee, Luisa Meroni, Utako Minai, Terry Parsons, Paul Pietroski, Tanya Reinhart, Luigi Rizzi, Anna Szabolcsi, Ovid Tzeng, Roger Wales and especially, Martin Hackl and Rosalind Thornton. Address for correspondence. Professor Stephen Crain, Macquarie Centre for Cognitive Science, Macquarie University, C5C Talavera Rd., North Ryde NSW 2109, Australia; e-mail: < [email protected] >. ‘Language and Speech’ is © Kingston Press Ltd. 1958 – 2008

Language and Speech

152

Disjunction in Universal Grammar

disjunction, according to which a statement of the form A or B is true if A is true, or if B is true, but not if both A and B are true. Despite the input, child speakers accept a statement of the form A or B as a description of a situation in which both A and B took place, as in classical logic. Consider the following context. You and a friend have just seen Max order some sushi and some pasta. Later you overhear your friend tell someone “Max ordered sushi or pasta.” Would you contradict your friend, saying “No, that’s wrong, Max ordered sushi and pasta”? That’s what adult speakers of English would do, but child speakers would not do this. For young children, “Max ordered sushi or pasta” correctly describes the case where Max ordered both sushi and pasta. Logic textbooks specify that A or B includes the possibility of both A and B, so child speakers of English appear to be more logical than adult speakers. As children grow up, their decisions change about when ‘or’ is appropriate, because their initial interpretation of ‘or’ clashes with how adult speakers use the term. But the difference in meaning between the ‘or’ of logic and the ‘or’ of English emerges late in language development. Why do adults understand or differently than children do? For adults, simple affirmative sentences of the form A or B are subject to an implicature of exclusivity. That is, the use of or usually implies “not both,” although it does not entail it. For adults, then, a simple statement of the form A or B is pragmatically odd (or infelicitous) as a description of a situation in which both A and B are true. This is why the use of or by adult speakers does not appear to conform to classical logic. The implicature of exclusivity derives from the availability of another statement, namely A and B, which is more informative than A or B. A and B is more informative because it is true in only one set of circumstances, in which both A and B are true. A statement of the form A or B is also true in circumstances in which both A and B are true, but such a statement is true in other circumstances as well, namely where only A, or only B, is true. So, the truth conditions associated with A and B versus A or B overlap, with A or B being true in a superset of the circumstances that verify A and B. Consequently, the expressions or and and form a scale, based on information strength, with and being more informative (i.e., stronger) than or. A pragmatic principle Be Cooperative (cf. Grice, 1975) entreats speakers to be as informative as possible. Upon hearing someone use the less informative (weaker) term on the scale, or, listeners assume that the speaker was being cooperative, so they infer that the speaker was not in position to use the stronger term and. If listeners believe, in addition, that the speaker is informed about the truth or falsity of the stronger term, then the speaker’s selection of the weaker term is taken to imply the negation of the stronger term: not both A and B.1 In short, adult use of or is governed by a scalar implicature of exclusivity. Adults therefore avoid using A or B in situations in which both A and B are clearly true. Consequently, the vast majority of children’s experience is consistent with the 1

Recently, Gennaro Chierchia has argued, convincingly in my view, that scalar implicatures are computed on-line as part of the recursive interpretation of a sentence. Since nothing hinges on it, the simple sketch of scalar implicatures I have given here adopts the more familiar pragmatic account associated with Grice.

Language and Speech

S. Crain

153

conclusion that natural language disjunction is exclusive-or, not inclusive-or (see Crain, Goro, & Thornton, 2006). Nevertheless, even children as old as five or six fail to compute scalar implicatures for sentences with or (Chierchia, Crain, Guasti, Gualmini, & Meroni, 2001; Chierchia, Guasti, Gualmini, Meroni, & Crain, 2004; Guasti, Chierchia, Crain, Foppolo, Gualmini, & Meroni, 2005; cf. Noveck, 2001; Papafragou & Musolino, 2003). Much has been written on this topic, but suffice it to say that, despite the input, children interpret or as the inclusive-or of classical logic in contexts where adults enforce an implicature of exclusivity (as well as in contexts where adults interpret or as inclusive-or). On an experience-based account of word learning, one would presumably expect children to use the truth conditions that are typically associated with ‘or’ in the input (i.e., those corresponding to exclusive-or), as the basis for assigning meanings to such words. But this, apparently, does not happen.2 The mystery thus becomes: why do children adopt the logical meaning of disjunction, inclusive-or, given that the majority of their experience directs them towards a different meaning of disjunction, namely an exclusive-or reading? The present proposal is that children’s knowledge that disjunction is inclusive-or comes from universal grammar, taking universal grammar to be a theory of the initial state of language acquisition.3 Universal grammar contains the linguistic principles that all languages share and all language learners draw upon in the course of language development. If inclusive-or comes from universal grammar, then it should be demonstrable that disjunction is inclusive-or in all natural languages, regardless of the abundant apparent counterexamples. It should also be demonstrable that young children, across languages, adopt inclusive-or as the basic meaning of disjunction, regardless of the input they encounter. To substantiate the first claim — that inclusive-or is the basic meaning of disjunction in universal grammar — I propose to establish that natural languages universally invoke inclusive-or in several linguistic contexts, where the implicature of exclusivity does not arise and where parametric differences across languages are not operative. These observations will then be supplemented by experimental studies demonstrating that children not only assign the basic inclusive-or meaning to disjunction in these linguistic contexts, but also in linguistic contexts in which adult speakers assign the truth conditions associated with exclusive-or, due to an implicature. 2

Similarly, the quantificational expression “some” forms a scale with other expressions (some, many, most, all ), based on information strength, with ‘some’ being the weakest term on the scale. The vast majority of input to children is therefore consistent with the possibility that ‘some’ means some, but not all. Nevertheless, children fail to compute scalar implicatures for sentences with ‘some’, and use this expression to mean some and possibly all, as in classical logic.

3

Universal Grammar also comes with a fixed number of parameters. Therefore, it anticipates that languages, and language learners, will exhibit a limited amount of variation. We discuss a constraint on cross-linguistic diversity and on grammar formation, called the continuity hypothesis, in Section 6.

Language and Speech

154


2 Universal Principle 1 In classical logic textbooks, the truth conditions associated with inclusive-or are the building blocks for de Morgan’s laws. One of de Morgan’s laws covers disjunctive statements: ¬ (A ∨ B) ⇒ ¬A ∧ ¬B. According to this law, a negative disjunctive statement ¬(A ∨ B) carries a “conjunctive” entailment ¬A ∧ ¬B. The conjunctive entailment of disjunction under negation follows only if disjunction is assigned the truth conditions associated with inclusive-or. Therefore, we can determine whether or not disjunction corresponds to inclusive-or in natural languages by seeing if statements with disjunction under negation license conjunctive entailments. That is the research strategy we will follow in articulating linguistic universals for natural language disjunction. There are at least three linguistic contexts in which (negative) statements with disjunction license conjunctive entailments across languages. This section is concerned with one of these linguistic contexts. Across languages, conjunctive entailments are licensed in sentences in which negation appears in a higher clause than the clause that contains disjunction (see Goro, 2004; Szabolcsi, 2002). Recall the context in which you and your friend watched Max order sushi and pasta. Suppose that your sister, Suzi, didn’t see Max order sushi, but she did see him order pasta. Later you overhear your friend tell someone “Suzi didn’t see Max order sushi or pasta.” Would you contradict your friend, saying “No, that’s wrong. Suzi saw Max order pasta.” That’s what adult speakers of English would do, and that’s what child speakers would do. Textbooks of logic would agree. In logic, not [A or B] excludes the possibility of A and the possibility of B. In English, statements of the form not [A or B] also exclude the possibilities of both A and B. The situation is more complicated in some other languages, however, where a distinction in the interpretation of disjunction is drawn between (a) structures in which negation and disjunction are clause-mates, and (b) structures in which negation resides in a higher clause than disjunction. When negation and disjunction reside in the same clause, some languages license a conjunctive entailment, as in de Morgan’s laws, but others do not. For example, in English and German, statements with negation and disjunction in the same clause generate conjunctive entailments, so “Max didn’t order pasta or sushi” means that Max didn’t order pasta, and didn’t order sushi. By contrast, statements of this form do not enforce a conjunctive entailment in some other languages, such as Japanese and Russian (see Section 6). Nevertheless, a conjunctive entailment is generated in all natural languages when negation appear in a higher clause than the clause that contains disjunction; that is, in statements of the form not S[A or B]. For example, the English statement “Suzi didn’t see Max order sushi or pasta” means that Suzi didn’t see Max order sushi, and Suzi didn’t see Max order pasta. And when such a statement is translated into Japanese, German, Russian, Hungarian, and so forth, the corresponding statements carry the same conjunctive entailment. In short, natural languages license conjunctive entailments as long as negation is in a higher clause than disjunction. Statements of the form not S[A or B] are interpreted as excluding the possibility of both A and B in all languages. As noted earlier, this requires the inclusive-or reading of disjunction, as in classical logic. For ease of exposition, I will refer to this configuration as nonlocal Language and Speech

S. Crain

155

negation. Here, then, is the first linguistic universal, which is based on observations made by Anna Szabolcsi: Disjunction licenses conjunctive entailments in the scope of nonlocal negation. Here are some examples from English (a), Chinese (b) and Japanese (c). In each case, the statement with disjunction generates a conjunctive entailment. (1) a. Mary didn’t say S[John speaks French or Spanish] b. Mali meiyou shuo-guo S[Yuehan hui shuo fayu huozhe xibanyayu] c. Mary-wa S[John-ga French ka Spanish-wo hanas-u]-to iwa-nakat-ta Before we move on, it is worth pointing out why the implicature of exclusivity, which is associated with or in affirmatives sentences, is canceled in negative statements such as the examples in (1). The reason is that negation reverses the scale of information strength. A negative statement with or is stronger than the corresponding statement with and, so the scalar implicature outlined earlier does not apply.

3 Universal Principle 2 A second universal linguistic principle is observed in sentences that contain certain focus expressions, such as English only and its variants in Japanese (dake) and in Chinese (zhiyou). Consider the following context. You and your friend see Max order some pasta. Your sister Suzi doesn’t like the look of the pasta, so she orders some sushi. Later you overhear your friend tell someone “Only Max ordered pasta or sushi.” Would you contradict your friend, saying “No, that’s wrong. Suzi ordered sushi.”? Adult speakers of English would do this, and child speakers of English would too. For children and adults, the sentence “Only Max ordered pasta or sushi” excludes the possibility that someone else (from a contextually relevant set) ordered pasta, and it excludes the possibility that someone else ordered sushi. And if this English sentence is translated into any other language (as far as we know), the resulting statement has the same truth conditions as the English statement. In short, natural languages license conjunctive entailments for disjunction in sentences that contain the English focus expression “only” or its variants in other languages. This is the second linguistic universal, which is based on work by Takuya Goro: Disjunction licenses conjunctive entailments in the scope of certain focus expressions. This second universal principle doesn’t mention negation, as did the first principle. Nevertheless, there are good reasons for supposing that negation is represented somehow in the interpretation of sentences with focus expressions like only. To illustrate, consider the English sentence Only Martin’s computer came with iChat or iSync. This sentence expresses two propositions. Following common parlance, we will call one of these the presupposition and the other the assertion (e.g., Horn, 1969, 1996). The presupposition is about Martin’s computer; it came with either iChat or iSync, or possibly both. The presupposition can be derived by deleting the focus expression only from the original sentence, yielding Martin’s computer came with iChat or iSync. There is an implicature of “exclusivity” in the presupposition, at least for many speakers. Language and Speech

156


The second proposition associated with the focus expression only is the assertion. The assertion of the sentence Only Martin’s computer came with iChat or iSync concerns individuals that are not mentioned in the sentence. To derive the assertion, it is common practice to partition sentences with a focus expression into (a) a focus element and (b) a contrast set. Focus expressions such as only are typically associated with a particular linguistic expression somewhere in the sentence. The associated expression is the focus element. More often than not, the focus element receives phonological stress. In the sentence Only Martin’s computer came with iChat or iSync, the focus element is Martin. The contrast set consists of individuals in the domain of discourse that are taken by the speaker and hearer to be alternatives to the focus element. These individuals should have been introduced into the conversational context before the sentence was produced; their existence is presupposed. In the present example, the contrast set consists of individuals being contrasted with Martin. The sentence would not be felicitous in the absence of this contrast set. In sentences with only, the assertion is about the contrast set. The assertion states that the members of the contrast set lack the property being attributed to the focus element. In the sentence Only Martin’s computer came with iChat or iSync, the assertion denies the claim that the computers belonging to the individuals in the contrast set came with iChat or iSync; their computers did not come with iChat or iSync. Notice that the assertion contains disjunction in the scope of (local) negation. Notice also that disjunction licenses a conjunctive entailment in the assertion: these computers didn’t come with iChat and they didn’t come with iSync. Here, again, disjunction has the truth conditions associated with inclusive-or, as in de Morgan’s laws. There is no implicature of exclusivity in the assertion. The implicature is canceled, once again, because the assertion makes a negative statement, and negative statements reverse the scale of information strength, such that or becomes more informative (stronger) than and. The pivotal point is that disjunction yields a conjunctive entailment when it appears in the assertion. The conjunctive entailment of disjunction is not derived from an overt negative expression, however. The sentence Only Martin’s computer came with iChat or iSync does not itself contain a negative expression; negation is nevertheless contained in the assertion of sentences with only and, in virtue of this, disjunction licenses a conjunctive entailment. Moreover, sentences with disjunction in the scope of a focus expression generate a conjunctive entailment in all natural languages (as far as we know). Here is an example from Chinese, where the focus expressions is zhiyou and the disjunction operator is huozhe. (2)

zhiyou Yuanhan hui shuo fayu huozhe xibanyayu only John can speak French or Spanish

This entails: ∀x [x ≠John] [not{x speaks French} and not{x speaks Spanish}] As a final comment, logic textbooks are silent on how disjunction is interpreted in sentences with a focus expression. This is a phenomenon of language, not logic (see Section 9). Language and Speech

S. Crain

157

4 Universal Principle 3 The third linguistic universal ties together linguistic phenomena that appear to be unrelated, namely (a) linguistic contexts that yield the conjunctive entailment of disjunction and (b) linguistic contexts that permit the (negative polarity item) any. Chierchia (2004) provides an account that unifies these linguistic phenomena. The third universal is a natural extension of Chierchia’s account. It is well known that negative polarity items like any, much, and ever are licensed by downward entailing expressions. An expression is downward entailing if it guarantees the validity of an inference from general statements to more specific statements. The examples in (3) illustrate three expressions that have this defining property of downward entailment, since it is valid to substitute claims about sets (speaking a Romance language) with claims about subsets of the original set (speaking French, speaking Spanish, speaking Italian …). Example (3a) shows that the subject phrase of the universal quantifier every is downward entailing. Similarly, the antecedent of a conditional statement is downward entailing, as shown in (3b), and so is the preposition before, as illustrated in (3c). (3)

a. Every student who speaks a Romance language likes to travel. ⇒ every student who speaks French likes to travel. b. If a student speaks a Romance language, she likes to travel. ⇒ if a student speaks French, she likes to travel. c. John went to Europe before learning a Romance language. ⇒ John went to Europe before learning French.

The negative polarity item any is licensed in the same three environments. This is illustrated in the (a) examples in (4) – (6). As the (b) examples show, however, any is not licensed in the predicate phrase of the universal quantifier every, or in the consequent clause of conditional statements, or following the preposition after. Such asymmetries are potentially problematic for language learners, as we will discuss in Section 8. (4)

a. Every linguist who agreed with any philosopher in this room. b. *Every linguist in this room agreed with any philosopher.

(5)

a. If any linguist enters the gym, then Geoff leaves. b. *If Geoff leaves, then any linguist enters the gym.

(6)

a. Geoff went to the gym before any linguist. b. *Geoff went to the gym after any linguist.

Remarkably, the linguistic environments that license the NPI any also generate conjunctive entailments for disjunction (cf. Chierchia, 2004; Crain, Gualmini, & Pietroski, 2005). Example (7) shows that or generates a conjunctive entailment in the subject phrase of the universal quantifier every; (8) shows that the antecedent of a conditional yields a conjunctive entailment; and (9) shows that a conjunctive entailment is generated by the preposition before. Language and Speech

158

(7)


a. Every student who speaks French or Spanish is in this room. b. ⇒ every student who speaks French is in this room and every student who speaks Spanish is in this room

(8)

a. If Ted or Kyle enters the gym, then Geoff leaves. b. ⇒ if Ted enters the gym, then Geoff leaves and if Kyle enters the gym, then Geoff leaves

(9)

a. Geoff went to the gym before Ted or Kyle. b. ⇒ Geoff went to the gym before Ted and Geoff went to the gym before Kyle

Moreover, conjunctive entailments are not generated for disjunction when it appears in positions where any is not tolerated. To take just one example, a conjunctive entailment is not generated when disjunction is in the predicate phrase of the universal quantifier every, as in (10). To see this, notice that (10a) and (10b) are not contradictory, as would be the case if (10a) made a conjunctive entailment. Similarly, there is no conjunctive entailment of or when it is in the consequent clause of conditionals, or when it follows the preposition after. In all of these linguistic contexts, the disjunction operator or carries an implicature of exclusivity. (10) a. Every student in this room speaks French or Spanish. b. every student in this room speaks French or Spanish, but no one speaks both languages c. * ⇒ every student in this room speaks French and every student in this room speaks Spanish From these observations, we derive the third semantic universal, borrowing from the theory advanced by Chierchia (2004): Disjunction licenses conjunctive entailments in the scope of downward entailing expressions. Example (11) provides evidence that the Chinese disjunction operator huozhe licenses a conjunctive entailment when it appears in the scope of the universal quantifier meige; (12) shows that the same is true in Japanese. (11) Meige [hui shuo fayu huozhe xibanyayu de] xuesheng dou tongguo-le kaoshi every can speak French or Spanish DE student DOU pass-Perf exam ‘Every student who speaks French or Spanish passed the exam’ ⇒ every student who speaks French passed the exam and every student who speaks Spanish passed the exam (12) [French ka Spanish-wo hanasu] dono gakusei-mo goukakushi- ta or -ACC speak every student pass-exam-past ‘Every student who speaks Icelandic or Swahili passed the exam’ ⇒ every student who speaks Icelandic passed the exam and every student who speaks Swahili passed the exam. Language and Speech

S. Crain

159

5 Universal Principle 4 Taken together, the three linguistic universals we have described invite the inference that there is a fourth universal: Natural language disjunction is inclusive-or. Aside from the inherent interest in identifying linguistic universals, such universals also lend themselves to compelling poverty-of-stimulus arguments, since these principles are not readily visible in the input to children, yet children are expected to “cognize” such principles at an early age. This is the next topic: how children initially interpret disjunction.

6 Child language: Universal Principle 1 Suppose you and your friend watch Max ordering his lunch. Max informs you that he might order some sushi or perhaps some pasta, but not both. Max tells the waiter that he doesn’t want both dishes, but you and your friend don’t see which dish Max turns down. Later, your friend says “Max didn’t order sushi or pasta.” Would you contradict this, saying “No, that’s wrong. Max ordered sushi or pasta, but we don’t know which”? Adult speakers of English would do this, and so would child speakers. However, adult speakers of Japanese would accept your friend’s statement (“Max didn’t order sushi or pasta”) as an accurate description of what had taken place. In English, statements of the form not [A or B] make a conjunctive entailment (the “neither” reading); such statements exclude the possibility of A and they exclude the possibility of B. In contrast, for adult speakers of Japanese, Hungarian, Russian, and many other languages, statements of the form ‘not [A or B]’ do not generate conjunctive entailments in simple negative statements, in which negation and disjunction are clause-mates. The translation of the sentence “Max didn’t order sushi or pasta” into one of these languages can be paraphrased as follows: It’s sushi or it’s pasta that Max didn’t order. So, in these languages, the translation of your friend’s “Max didn’t order sushi or pasta” would be judged to be an accurate description of the scenario above, in which Max didn’t order one of the dishes, but we don’t know which dish he did not order. This shows that simple negative sentences with disjunction do not receive a uniform interpretation across languages. In some languages (English, German, etc.), disjunction generates conjunctive entailments under local negation, whereas in other languages (Japanese, Hungarian, Russian, etc.) it does not. Nevertheless, disjunction generates conjunctive entailments in all languages if disjunction and negation are separated by a clause boundary, as we have already seen. The distinction is between disjunction under local negation, not VP [A or B], versus nonlocal negation, not S [A or B]. The bracket label, VP versus S, makes a difference. That is why the first universal principle mentions nonlocal (higher) negation: Disjunction licenses conjunctive entailments in the scope of nonlocal negation. Example (14) is another illustration of a simple negative sentence with disjunction in Japanese. Adult speakers of Japanese interpret (14) to mean that the pig didn’t eat the carrot or didn’t eat the pepper. Despite the appearance of the Japanese disjunction operator ka under local negation in surface syntax, ka is interpreted by adults as if it has scope over negation. Language and Speech

160


(14) Butasan-wa ninjin ka pi’iman-wo tabe-nakat-ta pig-TOP pepper or carrot-ACC eat-NEG-PAST Why is the interpretation of disjunction subject to cross-linguistic variation? Pursuing a suggestion by Szabolcsi (2002), Goro (2004) proposed that disjunction is a positive polarity item (like some in English) in one class of languages (Japanese, Hungarian, Russian, etc.), but it does not serve this role in another class of languages (English, German, etc.). By definition, a positive polarity item must be interpreted as if it were positioned outside the scope of negation, rather than within the scope of negation. This explains why the disjunction operator ka in the Japanese example (14) has the truth conditions associated with exclusive-or (not both), whereas or generates a conjunctive entailments (neither) in the corresponding sentence of English. In Japanese, disjunction is not interpreted inside the scope of local negation (despite appearances), so the implicature of exclusivity is enforced. Based on considerations of language learnability, Goro (2004) predicted that Japanese-speaking children would interpret the disjunction operator ka as licensing conjunctive entailments in simple negative sentences such as (14), just as English speaking children and adults do.4 This expectation is derived from the observation that the alternative values of the ‘positive polarity parameter’ for disjunction stand in a subset / superset relation, with English exemplifying the subset value of the parameter, and Japanese exemplifying the superset value. Goro reasoned that this situation would lead to a “subset problem” unless children acquiring Japanese initially select the parameter value corresponding to English; hence, Goro predicted that child speakers of Japanese would license conjunctive entailments in simple negative sentences with disjunction, whereas adult speakers do not license such entailments. The reason children are expected to behave more logically than adult speakers of Japanese, Goro suggested, is that all language learners must adhere to a principle of language acquisition called the semantic subset principle (Crain, Ni, & Conway, 1994). The semantic subset principle enforces an ordering on the values of certain parameters, where one value makes a sentence true in a subset of the circumstances that make it true on the other value. The semantic subset principle compels children to adopt the subset value of the parameter as their initial setting; this value is abandoned only on the basis of positive evidence in the local language. If children adopted the superset value instead, they would generate sentence meanings that are not licensed in the local language, in addition to ones that are licensed. This raises a familiar learnability problem: in the absence of negative evidence, children would be unable to purge their grammars of the unacceptable meanings. To avoid this problem, the semantic subset principle orders the initial value of certain parameters.5 4

To convey the “neither” interpretation, Japanese employs sentences with a ~mo ~mo construction, which is semantically similar to the use of conjunction (and) in English. This strategy would also be used by adult speakers to convey the meaning of the assertion of the focus expression dake (see Section 7).

5

The semantic subset principle governs the initial settings of parameters in Universal Grammar. The semantic subset principle does not, however, guide the development of word meanings. In particular, children are not expected to initially adopt the exclusive-or reading as the initial

Language and Speech

S. Crain

161

To investigate this solution to the “logical problem of language acquisition,” Goro and Akiba (2004) examined Japanese children’s interpretation of negated disjunctions in sentences like (14) (repeated here) using the Truth Value Judgment Task. (14) Butasan-wa ninjin ka pi’iman-wo tabe-nakat-ta pig-TOP pepper or carrot-ACC eat-NEG-PAST Adult Meaning: ‘The pig didn’t eat the pepper or the pig didn’t eat the carrot’ Goro and Akiba (2004) interviewed 30 Japanese-speaking children (mean age 5;3) as well as a control group of Japanese-speaking adults. On a typical trial, subjects were asked to judge whether or not (14) was an accurate description of a situation in which the pig had eaten the carrot but not the green pepper. The findings were precisely as Goro had predicted. First, Japanese-speaking adults uniformly accepted the target sentences. So adult speakers consistently assigned the “not both” reading of disjunction under local negation. Hence, adult speakers of Japanese accepted (14) because the pig had not eaten both the carrot and the green pepper. By contrast, child speakers of Japanese rejected the same sentences 75% of the time, because they assigned the “neither” interpretation, and it was false that the pig had eaten neither food. The findings are even more compelling once the data from four children who responded like adults were set aside. The remaining 26 children rejected the target sentences 87% of the time. To summarize, child speakers of Japanese interpret disjunction under negation (NEG > OR), such that they generate a conjunctive entailment as in de Morgan’s law: ¬(A ∨ B) ⇒ ¬A ∧ ¬B. Adult speakers of Japanese, by contrast, interpret disjunction as having scope over negation (OR > NEG), so de Morgan’s laws are not operative for them. This makes it look as if adult speakers of these languages violate de Morgan’s laws in simple negative sentences. But of course this is not what’s going on. We have already seen that adult speakers of Japanese, and all other languages, adhere to de Morgan’s laws when disjunction is in a lower clause than negation. The difference between children and adults is that children adopt a more restrictive (subset) value of a parameter that governs the scopal interpretation of disjunction under local negation. At some point in language development, child speakers of Japanese come to adopt the less restrictive setting of the parameter in response to the input. Thereafter, disjunction has scope over negation (OR > NEG) for child speakers, just as it does for adults. The pattern of responses by Japanese-speaking children are difficult to explain on a experience-dependent account of language development, since Japanese-speaking children interpreted negated disjunctions as licensing conjunctive entailments, whereas Japanese-speaking adults did not. On the other hand, the findings are consistent with the continuity hypothesis, according to which child language is expected to diverge from the local adult language, but only in ways that adult languages can differ from interpretation of disjunction despite the fact that this reading validates sentences in a subset of the circumstances that are associated with the inclusive-or reading, and despite the fact that adult use of disjunction is, by and large, consistent with exclusive-or.

Language and Speech

162


each other (see, e.g., Crain, 1991, 2002; Crain, Goro, & Thornton, 2006; Crain & Pietroski, 2001, 2002; Thornton, 1990, 2004). Based on the semantic subset principle, the theory of Universal Grammar anticipates that children learning any language should interpret disjunction as inclusive-or, regardless of the input children encounter. The fact that this was found in a language in which the input from adults violates de Morgan’s laws provides further evidence for the continuity assumption (see Jing, Crain, & Hsu, 2005, for a similar analysis of child Chinese).

7Child language: Universal Principle 2 The linguistic universal II is also difficult to explain on an experience-dependent approach to language development (e.g., Tomasello, 2000, 2003): Disjunction licenses conjunctive entailments in the scope of certain focus expressions. The input to children presumably does not contain systematic information about the assertion of the focus expression only, that is, the entailment about the contrast set. Recent experimental research has sought to determine whether or not children know that sentences with the focus expression only contain negation, or its semantic equivalent, making only downward entailing in the assertion.6 As noted earlier, 4- to 5-year-old children appear to know that or licenses conjunctive entailments in certain downward-entailing contexts, for example, under negation, and in the Restrictor of the universal quantifier every. So, children’s interpretation of or can be used to assess their knowledge of the semantics of only (Goro, Minai, & Crain, 2005). It seems unlikely that there is relevant evidence in the input about the entailment of sentences with only. On the other hand, if children do not acquire knowledge of the entailment from experience, then children should have to access this knowledge regardless of differences in the language they are learning. With these objectives in mind, Goro, Minai, and Crain (2005) conducted several experiments, with English-speaking children (using sentences with only … or) and with Japanese-speaking children (using dake… ka …). The research strategy was to investigate their interpretations of disjunction in the two meaning components of sentences with the focus operator only / dake. One of the test sentences is given in (15). (15) a. Only Bunny Rabbit will eat a carrot or a green pepper. b. Usagichan-dake-ga ninjin ka piiman-wo taberu-yo. rabbit-only-NOM carrot or green pepper-ACC eat-dec Under Horn’s (1969; 1996) analysis, the meaning of (15) can be partitioned into the two conjoined propositions in (16). (16) a. Presupposition: Bunny Rabbit will eat a carrot or a green pepper b. Assertion: Everyone else (being contrasted with Bunny Rabbit) will not eat a carrot or a green pepper 6

There is much debate in the recent literature about whether or not the focus expression only is downward entailing (see e.g., von Fintel, 1999).

Language and Speech

S. Crain

163

We conducted experiments with English-speaking and Japanese-speaking children, to compare their linguistic behavior. The experiments in English and Japanese were identical in design, with only minimal changes in some of the toy props. The experiment adopted the Truth Value Judgment task, in the prediction mode (Chierchia et al., 2001; Crain, & Thornton, 1998). There were two experimenters. One of them acted out the stories using the toy props, and the other manipulated the puppet, Kermit the Frog. While the story was being acted out, the puppet watched along with the child subject. In each trial, the story was interrupted — after the introduction of the characters and a description of the situation — so that the puppet could make a prediction about what he thought would happen. Then, the story was resumed, and its final outcome provided the experimental context against which the subject evaluated the target sentence, which had been presented as the puppet’s prediction. The puppet repeated his prediction at the end of each story, and then the child subject was asked whether the puppet’s prediction had been right or wrong. Twenty-one English-speaking children (mean age 5;0) participated in the experiment, and 20 Japanese-speaking children (mean age 5;4). The experiments had two main test conditions, and a number of filler trials. One test condition corresponded to the presupposition of the target sentences, and the other corresponded to the assertion. The first condition made the sentence true for adult speakers of both languages. For the English sentence Only Bunny Rabbit will eat a carrot or a green pepper, the presupposition is the sentence minus the focus expression: Bunny Rabbit will eat a carrot or will eat a green pepper. This was true in Condition 1 because, as the story unfolded, it turned out that Bunny Rabbit did eat a carrot, but not a green pepper. The other individuals in the story, Winnie the Pooh and Cookie Monster, did not eat either of these food items. This condition is graphically represented in (17). (17) Condition 1 Carrot

Green Pepper

Bunny Rabbit

√

*

Winnie the Pooh

*

*

Cookie Monster

*

*

The assertion of the test sentences was investigated in Condition 2, as represented in (18). As in Condition 1, Bunny Rabbit ate a carrot, but not a green pepper. But, in Condition 2, one of the other characters, Cookie Monster, ended up eating a green pepper. This scenario was used to assess children’s knowledge of the assertion of sentences with a focus expression. The assertion of the English sentence Only Bunny Rabbit will eat a carrot or a green pepper is a proposition about the contrast set, namely that the members of the contrast set lack the property attributed to the element in focus: The others (contrasted with Bunny Rabbit) will not eat a carrot or a green pepper. In the assertion, or appears in the scope of negation, and is therefore expected to license a conjunctive entailment — that the others will not eat a carrot and will not eat a green pepper. Consequently, if children assign the inclusive-or interpretation to or in the assertion, they should reject the test sentence in Condition 2. Language and Speech

164


(18) Condition 2 Carrot

Green Pepper

Bunny Rabbit

√

*

Winnie the Pooh

*

*

Cookie Monster

*

√

Before we turn to the research findings, it is worth considering how children learn the assertion of sentences with the focus expression only. Adult speakers of English might be able to provide relevant input, but it is not clear that this is even possible in the case of Japanese. The assertion in both languages is the following proposition: Everyone except Bunny Rabbit will not eat a carrot or a green pepper.7 In both English and Japanese, disjunction appears in the scope of local negation. In English, disjunction under local negation licenses a conjunctive entailment, as needed for the assertion. However, in Japanese, disjunction cannot be interpreted in the scope of local negation. Suppose an adult speaker of Japanese tries to convey the content of the assertion: Everyone except Bunny Rabbit will not eat a carrot or a green pepper. The most straightforward Japanese counterparts to the English statement of the assertion are given in (19). The problem for the learner is that the statement expressed in (19) does not convey the intended (neither) interpretation that is entailed by the assertion. In fact, the statement expressed in (19) is true in the discourse context under consideration. Since neither Winnie the Pooh nor Cookie Monster ate a carrot, it is true that everyone except Bunny Rabbit didn’t eat a carrot or will not eat a green pepper; they did not eat a carrot. But this is not the assertion made by (15). Disjunction in the assertion of (15) generates the conjunctive entailment: everyone except Bunny Rabbit will not eat a carrot and will not eat a green pepper. min'na / zen'in-ga ninjin ka piiman-wo tabe-nakat-ta (19) Bunny Rabbit igai-no Bunny Rabbit except-gen everyone-nom carrot or pepper-acc eat-neg-past Meaning: ‘Everyone except BR didn’t eat the carrot OR didn’t eat the pepper’ * ‘Everyone except BR didn’t eat the carrot AND didn’t eat the pepper’ To convey the intended (neither) interpretation of the assertion, then, adult speakers of Japanese must come up with an alternative sentence structure that does not contain disjunction under local negation (see fn. 3). Clearly, Japanese-speaking children do not learn the meaning of the assertion of sentences with dake by watching how adults use the disjunction operator ka in sentences like (19). The question of how Japanese-speaking children learn what ka means in sentences with dake, such as (15), poses a serious challenge for an experience-based account of language development. 7

In Japanese, negation must be attached to the verb, making this paraphrase quite natural. In English, other options are possible, such as a statement with nobody, for example.

Language and Speech

S. Crain

165

We have already provided evidence that Japanese-speaking children access the inclusive-or interpretation of the disjunction operator ka under local negation, so they should also be expected to license the conjunction entailment of disjunction in sentences with the focus expression dake. And, as a matter of record, both Englishspeaking children and Japanese-speaking children consistently accepted the test sentences in Condition 1, and consistently rejected the test sentences in Condition 2. The acceptance rate for over 90% for Condition 1, and the rejection rate was over 90% for Condition 2. The two groups of children showed no significantly different behavior in interpreting disjunction in sentences containing the focus operators only versus dake. Most crucially for our purpose, the high rejection rate in Condition 2 shows that children assigned conjunctive entailments to disjunction in the assertion component of the test sentences. This, in turn, suggests that children assigned the same semantics to the disjunction operator in each language, despite the differences in the input from adult speakers. Children’s consistent rejections of the test sentences in Condition 2 provide compelling evidence that they are computing the assertion that is associated with the focus expression only. As we saw, the assertion expresses a (negative) proposition about a set of individuals that are being contrasted with the element in focus. The findings clearly establish children’s ability to compute such contrast sets, although this ability has recently been questioned (cf. Paterson, Liversedge, Rowland, & Filik, 2003). There is one loose end to tie up. The question remains why adult speakers of languages which do not interpret disjunction in the scope of local negation, such as Japanese, Hungarian, Russian, Chinese, and so forth, nevertheless generate a conjunctive entailment for disjunction when it is interpreted in the assertion of sentences with certain focus expressions. Intuitively, the answer is that negation is “covertly” supplied in the assertion of sentences with these focus expressions. Presumably, because negation is covert, it does not trigger the positive polarity effect that is encoded in the “disjunction” parameter value for these languages (for detailed analysis, see Goro, 2004).

8 Child language: Universal Principle 3 Recall the third putative linguistic universal: disjunction licenses conjunctive entailments when it appears in the scope of downward entailing expressions. One of the consequences of this universal is a striking asymmetry in the interpretation of disjunction depending on whether it appears in the subject phrase or in the predicate phrase of the universal quantifier, for example, every in English. Children’s knowledge of the asymmetry involving the universal quantifier has been investigated in the literature. Before we report the findings of these investigations, it will be useful to describe the semantics of the universal quantifier in more detail. The universal quantifier is a determiner, like no, some, both, t he, t hree, and so forth. Structurally, determiners combine with a noun (student) or a noun phrase (student in this room) to form a grammatical unit — like every student or every student in this room. The noun (phrase) that every combines with what is called its Restrictor (abbreviated by the subscript ‘R’ in the schema in (20) below). Once every combines with its Restrictor, the entire unit can then be combined with a predicate phrase (e.g., Language and Speech

166


swims, speaks French or Spanish). The predicate phrase is called the Scope of the universal quantifier (abbreviated ‘S’ in 20). If the disjunction operator or appears in the Scope of every, it has an “disjunctive” interpretation. For example, the sentence Every student speaks French or Spanish implies that every student speaks French or Spanish, and at least one student speaks one of these languages, but not both. We attribute this “disjunctive” reading in the Scope of every to a scalar implicature; this interpretation is not taken as evidence of an ambiguity in the meaning of or in natural language. (20) Every R[……….…] S […. or …….] = “disjunctive” reading Every R[… or …] S [……………] = conjunctive entailment Example (21) shows that the negative polarity item any is permitted in the Restrictor of the universal quantifier every, but not in its Scope. This illustrates the descriptive generalization that any may only appear in linguistic contexts in which disjunction licences a conjunctive entailment. (21) Every R[… any …] S […*any …] We now turn to the literature on child language. Several studies have investigated the truth conditions children associate with disjunction in the Restrictor and in the Scope of the universal quantifier (e.g., Boster & Crain, 1994; Gualmini, Meroni, & Crain, 2003). Using the Truth Value Judgment task, children were asked to evaluate sentences like those in (22) and (23), produced by a puppet, Kermit the Frog. (22) Every woman bought eggs or bananas. (23) Every woman who bought eggs or bananas got a basket. In one condition, sentences like (22) were presented to children in a context in which some of the women bought eggs, but none of them bought bananas. The child subjects consistently accepted test sentences like (22) in this condition, showing that they assigned a “disjunctive” interpretation to or in the Scope of the universal quantifier, every. In a second condition, children were presented with sentences like (23) in a context in which women who bought eggs received a basket, but not women who bought bananas. The child subjects consistently rejected the test sentences in this condition. This finding is taken as evidence that children generated a conjunctive entailment for disjunction in the Restrictor of every. This asymmetry in children’s responses in the two conditions demonstrates their knowledge of the asymmetry in the two grammatical structures associated with the universal quantifier — the Restrictor and the Scope. Taken together, the findings are compelling evidence that children know that the Restrictor of every is downward entailing, but not its Scope. So much for children’s asymmetrical interpretation of disjunction in the Scope and Restrictor of sentences with the universal quantifier, every. What about the expected asymmetry in the licensing of any? There are only a handful of studies bearing on the development of polarity sensitivity in children, but what little is known is consistent with the conclusion that young children produce and avoid negative polarity items in the same linguistic contexts as adults do (O’Leary & Crain, 1994: Thornton, 1995; van der Wal, 1996). An experiment by O’Leary and Crain is representative. The experimental technique was a Truth Value Judgment task with an elicitation component. In the task, the puppet, Kermit the Frog, often produced false Language and Speech

S. Crain

167

descriptions of the events that had taken place in the story. Whenever Kermit failed to accurately state what had happened in a story, children were asked to say “what really happened.” The experimenter who was manipulating Kermit produced sentences like those in (24) and (25), to which the child subject responded as indicated. (24) Kermit: Every dinosaur found something to write with. Child: No, this one didn’t find anything to write with. (25) Kermit: Only one of the reindeer found anything to eat. Child: No, every reindeer found something to eat. In the condition illustrated by (24), Kermit’s statements had a universal quantifier every, which does not tolerate negative polarity items, such as anything, in its Scope; instead, the (positive polarity) expression something was used. Eleven children (mean age 4;10) participated in the study. These children’s responses frequently contained the negative polarity item anything in linguistic contexts that license it. In another condition, illustrated in (25), Kermit’s statements contained the negative polarity item anything. However, in correcting Kermit, children consistently used the universal quantifier every, so the linguistic context forced children to avoid repeating anything; they typically produced something instead. The findings make it clear that children have mastered some, if not all, of the requisite knowledge of downward entailment, which underlies the appropriate use and avoidance of negative polarity items.

9 Logic vs. Language The findings reported in this paper invite the conclusion that children know that natural language disjunction is inclusive-or, as in classical logic. This may give the impression that natural language and logical reasoning go hand in hand in universal grammar. And this, in turn, may lead to the speculation that what is innately specified in the mind / brains of language learners is the conceptual apparatus used in logical reasoning, rather than specific contingent properties of natural language. Upon closer examination, however, several specific contingent properties of natural language have emerged in the course of these deliberations. First, we have seen that natural languages manifest a distinction between structures in which disjunction and negation appear in the same clause, and ones in which negation appears in a higher clause than disjunction. Although the distinction between VP and S is needed to represent the first universal principle, there is no corresponding labeled brackets in classical logic. Second, some natural languages exhibit an inverse scope interpretation (rather than the surface scope relations) in structures in which disjunction (a positive polarity item) and negation appear in the same clause. There is nothing like inverse scope relations in classic logic. Third, the assertion of certain focus expressions has no counterpart in logic. Finally, the conjunctive entailment of disjunction does not arise simply with negation, as in de Morgan’s laws, but the same entailment is licensed by a host of linguistic expressions, namely ones that are downward entailing. There are no logical counterparts to many of these downward entailing expressions. manuscript received:

03. 19. 2006

manuscript accepted:

11. 01. 2006

Language and Speech

168


References BOSTER, C., & CRAIN, S. (1994). The interaction of every and or in child language. In Early cognition and the transition to language, University of Texas Working Papers, Austin, TX. CHIERCHIA, G. (2004). Scalar implicatures, polarity phenomena, and the syntax / pragmatics interface. In A. Belleti & L. Rizzi (Eds.), Structures and beyond. Oxford: Oxford University Press. CHIERCHIA, G., CRAIN, S., GUASTI, M. T., GUALMINI. A., & MERONI, L. (2001). The acquisition of disjunction: Evidence for a grammatical view of scalar implicatures. Proceedings of the 25th Boston University Conference on Language Development (pp.157 – 168). Somerville, MA: Cascadilla Press. CHIERCHIA, G., GUASTI, M. T., GUALMINI. A., MERONI, L., & CRAIN, S. (2004). Semantic and pragmatic competence in children and adult’s interpretation of ‘or’. In Noveck & S. Wilson (Eds.), Experimental pragmatics, I (pp. 283 – 300). London: Palgraves. CRAIN, S. (1991). Language acquisition in the absence of experience. Behavioural and Brain Sciences, 4, 597 – 650. CRAIN, S. (2002). The continuity assumption. In I. Lasser (Ed.), The process of language acquisition (pp. 3 – 24). New York: Peter Lang. CRAIN, S., GARDNER, A., GUALMINI, A., & RABBIN, B. (2002). Children’s command of negation. Proceedings of the Third Tokyo Conference on Psycholinguistics (pp.71 – 95). Tokyo: Hituzi Publishing Company. CRAIN, S., GORO, T., & THORNTON, R. (2006). Language acquisition is language change. Journal of Psycholinguistic Research, 35(1), 31 – 49. CRAIN, S., GUALMINI, A., & PIETROSKI, P. (2005). Brass tacks in linguistic theory: Innate grammatical principles. Proceedings of the First Annual AHRB Conference on Innateness and the Structure of the Mind (pp.175 –197). University of Sheffield, England. CRAIN, S., NI, W., & CONWAY, L. (1994). Learning, parsing, and modularity. In C. Clifton, L. Frazier, & K. Rayner (Eds.), Perspectives on sentence processing (pp.443 – 467). Hillsdale, NJ: Lawrence Erlbaum Associates. CRAIN, S., & PIETROSKI, P. (2001). Nature, nurture and Universal Grammar. Linguistics and Philosophy, 24, 139 – 185. CRAIN, S. & PIETROSKI, P. (2002). Why language acquisition is a snap. The Linguistic Review, 19(1/2), 163 – 183. CRAIN, S., & THORNTON, R. (1998). Investigations in Universal Grammar: A guide to experiments on the acquisition of syntax and semantics. Cambridge, MA: MIT Press. GORO, T. (2004). The emergence of Universal Grammar in the emergence of language: The acquisition of japanese logical connectives and positive polarity. Unpublished ms, University of Maryland at College Park. GORO, T., & AKIBA, S. (2004). The acquisition of disjunction and positive polarity in Japanese. Proceedings of the 23rd West Coast Conference on Formal Linguistics (pp. 251 – 264). Summerville, MA: Cascadilla Press. GORO, T., MINAI, U., & CRAIN, S. (2005). Two disjunctions for the price of only one. Proceedings of the 29th Annual Boston University Conference on Language Development (pp.228 – 239). Summerville, MA: Cascadilla Press. GRICE, H. P. (1975). Logic and conversation. In P. Cole & J. Morgan (Eds.), Syntax and semantics 3: Speech acts (41 – 58). New York: Academic Press. GUALMINI, A., & CRAIN, S. (2002). Why no child or adult must learn de Morgan’s laws. Proceedings of the 24th Annual Boston University Conference on Language Development (pp.367 – 378). Summerville, MA: Cascadilla Press. GUALMINI, A., CRAIN, S., MERONI, L., CHIERCHIA, G., & GUASTI, M. T. (2001). At the semantics / pragmatics interface in child language. Proceedings of Semantics and Linguistic Theory, 11, New York University. Language and Speech

S. Crain

169

GUALMINI, A., MERONI, L., & CRAIN, S. (2003). An asymmetric universal in child language. Proceedings of Sinn und Bedeutung VI (pp.136 – 148). Arbeitspapiere des Fachbereichs Sprachwissenschaft, Konstanz, Germany. GUASTI, M. T., CHIERCHIA, G., CRAIN, S., FOPPOLO, F., GUALMINI, A., & MERONI, L. (2005). Why children and adults sometimes (but not always) compute implicatures. Language and Cognitive Processes, 20, 667 – 696. HORN, L. (1969). A presuppositional approach to only and even. Proceedings of the Chicago Linguistic Society, 5, 98 – 107. HORN, L. (1996). Presupposition and implicature. In S. Lappin (Ed.), Handbook of contemporary semantic theory (pp. 299 – 319). Oxford: Backwell. JING, C., CRAIN, S., & HSU, C. (2005). The interpretation of focus in Chinese: Child versus adult language. Proceedings of the Sixth Tokyo Conference on Psycholinguistics. Tokyo: Hituzi Publishing Company. MINAI, U., GORO, T., & CRAIN, S. (2006). Covert downward entailment in child English and Japanese. Proceedings of GALANA, Hawaii. NOVECK, I. A. (2001). When children are more logical than adults: Experimental investigations of scalar implicatures. Cognition, 78(2), 165 – 188. O’LEARY, C., & CRAIN, S. (1994). Negative Polarity (a positive result) and Positive Polarity (a negative result). Presented at the 18th Annual Boston University Conference on Language Development, Boston, MA. PAPAFRAGOU, A., & MUSOLINO, J. (2003). Scalar implicatures: Experiments at the semanticspragmatics interface. Cognition, 86(3), 253 – 282. PATERSON, K. L., LIVERSEDGE, S. P., ROWLAND, C., & FILIK, R. (2003). Children’s comprehension of sentences with focus particles. Cognition, 89, 263 – 294. SZABOLCSI, A. (2002). Hungarian disjunctions and positive polarity. In I. Kenesei & P. Siptar (Eds.), Approaches to Hungarian, 8 (pp. 217 – 241). Budapest: Akademiai Kiado. THORNTON, R. (1990). Adventures in long-distance moving: The acquisition of complex wh-questions. Doctoral dissertation, University of Connecticut, Storrs. THORNTON, R. (1995). Children’s negative questions: A production / comprehension asymmetry. In J. Fuller, H. Han, & D. Parkinson (Eds.), Proceedings of Eastern States Conference on Linguistics. Cornell, New York: CLC Publications. THORNTON, R. (2004). Why continuity. In A. Brugos, L. Micciulla, & C. E. Smith (Eds.), Proceedings of the 28th Boston University Conference on Language Development (pp.620 – 632). Somerville, MA: Cascadilla Press. TOMASELLO, M. (2000). First steps toward a usage-based theory of language acquisition. Cognitive Linguistics, 11, 61 – 82. TOMASELLO, M. (2003). Constructing a language: A usage-based theory of language acquisition. Cambridge, MA: Harvard University Press. Van, der WAL, S. (1996). Negative polarity items and negation: Tandem acquisition. Groningen Dissertations in Linguistics, 17, University of Groningen. Von FINTEL, K. (1999). NPI-licensing, Strawson entailment, and context dependency. Journal of Semantics, 16, 97 – 148.

Language and Speech