Download Early Language Acquisition: Children's Understanding of Relative Clauses and more Lecture notes Construction in PDF only on Docsity!
Haskins Laboratories Status Report on Speech Research 1989, SR-99 / 100, 118-
Competence and Performance in Child Language*
Stephen Craint and Janet Dean Fodortt
1. INTRODUCTION
This paper presents the results of our recent experimental investigations of a central issue in linguistic theory: which properties of human language are innately determined? There are two main sources of information to be tapped to find the answer t9 this question. First, universal properties of human languages are plausibly (even if not necessarily) taken to be innately determined. In addition, properties that emerge in children's language in the absence of decisive evidence in their linguistic input are reasonably held to be innate. Clearly, it would be most satisfactory if these two diagnostics for what is innate agreed with each other. In some cases they do. For example, there is a universal principle favoring transformational movement of phrases rather than oflexical categories e.g., topicalization of noun phrases but not of nouns. To the best of our knowledge children abide by this principle; they may hear sentences such as Candy, you can't have now~ but they don't infer that nouns can be topicalized. If they did, they would say things like *Vegetables, I won't eat the. But this is not an error characteristic of children. Instead, from the moment they produce topicalized constructions at all, they apparently produce correct NP- topicalized forms such as The vegetables, I won't eat. In recent years, this happy convergence of results from research on universals and research
This research was supported in part by NSF Grant BNS 84.18537, and by a Program Project Grant to Haskins Laboratories from the National Institute of Child Health and Human Development (HD·01994). The studies reported in this paper were conducted in collaboration with several friends and colleagues: Henry Hamburger, Paul Gorrell, Howard Lasnik Cecile McKee, Keiko Murasugi, Mineharu Nakayama, Jay~ Sarma and Rosalind Thornton. We thank them for their permission to gather this work together here.
118
on ~cquisition has been challenged by expenmental studies reporting various syntactic failures on the part of children. The children in these experiments are apparently violating putatively universal phrase structure principles or constraints on transformations. Failure to demonstrate early knowledge of syntactic principles is reported by Jakubowicz (1984), Lust (1981), Matthei (1981, 1982), Phinney (1981), Roeper (1986), Solan and Roeper (1978)
Tavakolian (1978, 1981) and Wexler and Chie~
(1985). Some explanation is clearly called for if a syntactic principle is respected in all adult languages but is not respected in the language of children. Assuming that the experimental data accurately reflect children's linguistic competence, there are several possible responses to the unaccom- modating data. The most extreme would be to give up the innateness claim for the principle in question. One might look for further linguistic data which show that it isn't universaL Or one might abandon the hypothesis that all universal prin~iples are innate. For instance, Matthei (1981) obtamed results that he interpreted as evidence that universal constraints on children's interpretation of reciprocals are learned not
innate. However, this approach is plausible o~ly if
one ~an offer so~e other explanation (e.g., functIonal explanatIon) for why the constraints should be universal. But this is not always easy; as Ch~msky (1986) has emphasized, many propertIes of natural language are arbitrary and have no practical motivation. A different response to the apparent failure of children to respect constraints believed to be ~nnate. is to argue that the constraints are as yet mapphcable to their sentences. The claim is that as soon as a child's linguistic analyses have reached the level of sophistication at which a
The Perception of Phonetic Gestures 117
Stoll, G. (1984). Pitch of vowels: Experimental and theoretical investigation of its dependence on vowel quality. Speech Communication, 3, 137-150. Studdert-Kennedy, M. (1986). Two cheers for direct realism. Journal of Phonetics; 14, 99-104. Studdert-Kennedy, M., &: Shankweiler, D. (1970). Hemispheric specialization for speech perception. Journal of the Acoustical Society of America, 48, 579-594. VanDerVeer, N. (1979). Ecological acoustics: Human perception of entlironmental sounds. Unpublished doctoral dissertation, Cornell University. Warren, W. &: Verbrugge, R. (1984). Auditory perception of breaking and bouncing events: A case study in ecological acoustics. Journal of Experimental Psychology: Human Perception and Performance, 10, 704-712. Whalen, D. (1984). Subcategorical mismatches slow phonetic judgments. Perception and Psychophysics, 35, 49-64. Whalen, D. &: Liberman, A. (1987). Speech perception takes precedence over nonspeech perception. Science, 237,169-171.
FOOTNOTES
"In I. G. Mattingly &: M. Studdert-Kennedy (Eds.), Modularity and the motor theory of speech perception. Hillsdale, NJ: Lawrence Erlbaum Associates, in press. t Also Dartmouth College, Hanover, New Hampshire. tt Also University of Connecticut, Storrs. Now at the University of California at Riverside, Department of Psychology. 1 There is a small qualification to the claim that listeners cannot tell what contributions visible and audible information each have to their perceptual experience in the McGurk effect. Massaro (1987) has shown that effects of the video display can be reduced but not eliminated by instructing subjects to look at, but to ignore, the display. 2Liberman et al. identify a cipher as a system in which each unique unit of the message maps onto a unique symbol. In contrast, in a code, the correspondence between message unit and symbol is not 1:1. 3Liberman et al. propose to replace the more conventional view of the features of a phoneme (for example, that of Jakobson, Fant &: Halle, 1951) with one of features as "implicit instructions to separate and independent parts of the motor machinery" (p. 446). 4With one apparent slip on page 2: "The objects of speech perception are the intended phonetic gestures of the speaker, represented in the brain as invariant motor commands ...." Sane can certainly challenge the idea that listeners recover the very gestures that occurred to produce a speech signal. Obviously there are no gestures at all responsible for most synthetic speech or for "sine-wave speech" (e.g., Remez, Rubin,
Pisoni, &: Carrell, 1981) and quite different behaviors underlie a parrot's or mynah bird's mimicking of speech. The claim that we argue is incontrovertible is that listeners recover gestures from speech-like signals, even those generated in some other way. (We direct realists [Fowler, 1986a,b] would also argue that "misperceptions" (hearing phonetic gestures where there are none) can only occur in limited varieties of ways-the most notable being signals produced by certain mirage-producing human artifacts, such as speech synthesizers or mirage- producing birds. Another, however, possibly, includes signals produced to mimic those of normal speakers by speakers with pathologies of the vocal tract that prevent normal realization of gestures.) 6There are two almost orthogonal perspectives from which perception can be studied. On the one hand, investigators can focus on processes inside the perceiver that take place from the time that a sense organ is stimulated until a percept is achieved or a response is made to the input. On the other hand, they can look outside the perceiver and ask what, in the environment, the organism under study perceives, what information in stimulation to the sense organs allows perception of the things perceived, and finally, whether the organisms in fact use the postulated information. Here we focus on this latter perspective, most closely associated with the work of James Gibson (e.g., 1966; 1979; Reed &:Jones, 1982). 7It is easy to find examples in which perception is heteromorphic with respect to the proximal stimulation and homomorphic with respect to distal events-looming, for example. We can also think of some examples in which perception appears homomorphic with respect to proximal stimulation, but in the examples we have corne up with, they are homomorphic with respect to the distal event as well (perception of a line dfawn by a pencil, for example), and so there is no way to decide whether perception is of the proximal stimulation or of the distal event. We challenge the motor theorists to provide an example in which perception is homomorphic with structure in proximal stimulation that is not also homomorphic with distal event structure. These would prOVide convincing cases of proximal stimulation perception. 8Bregman (1987) considers duplex perception to disconfirm his "rule of disjoint allocation" in acoustic scene analysis by listeners. According to the rule, each acoustic fragment is assigned in perception to one and only one environmental source. It seems, however, that duplex perception does not disconfirm the rule. 9Using a more sensitive, AXB, test, however, we have found that listeners can match the metal door chirp, rather than a wooden door chirp, to the metal door slam at performa~ce levels considerably better than chance.
120 Crain^ and^ Fodor
2. CHILDREN'S ERRORS IN
COMPREHENSION
In this section we attempt to identify and isolate several components of language-related skills, in order to gain a better understanding of each, and to clarify the relationship between the innateness hypothesis and early linguistic knowledge. Very little work has been done on this topic. The majority oflanguage development studies seem to take it for granted that the experimental paradigms provide a direct tap into the child's linguistic competence. An important exception is a study by Goodluck and Tavakolian (1982), in which improved performance on a relative clause comprehension task resulted from simplification of other aspects of the syntax and semantics of the stimulus sentences (Le., the use of intransitive rather than transitive relative clauses, and relative clauses with one animate and one inanimate noun phrase rather than two animates). The success of these manipulations is exactly in accord with our general hypothesis about the relation between competence and performance. As other demands on the child's performance are reduced, greater competence is revealed. Our experiments focus on three factors involved
. in many child language experiments which may interfere with estimation of the extent of children's linguistic knowledge in tasks which are designed to measure sentence comprehension. These factors-parsing, presupposition and plans-are of interest in their own right, but have received very little attention in previous research on syntax acquisition. In this section we will review our. recent work on these topics. In the following section we will tum to an alternative research strategy for assessing children's knowledge, the technique of elicited production. Parsing. Sentence parsing is a complex task which is known to be governed (in adults) by various decision strategies that favor one structural analysis over another where both are compatible with the input word sequence. Even adults make parsing errors, and it would hardly be surprising, given the limited memory and attention spans of children, to discover that they do too. These parsing preferences must somehow be neutralized or factored out of an experimental task whose objective is the assessment of children's knowledge of syntactic rules and constraints. Plans. The formation of an action plan is an important aspect of any comprehension task
involving the manipulation .of toys or other objects. If the plan for manipulating objects appropriately in response to a test sentence is necessarily complex to formulate or to execute, its difficulty for a child subject may mask his correct comprehension of the sentence. Thus we need to
. develop a better understanding of the nature and relative complexity of such plans, and also to devise experimental paradigms in which their impact on performance is minimized. Presuppositions. A variety of pragmatic considerations must also be taken into account, such as the contextual fixing of deictic reference, obedience to cooperative principles of conversation, and so forth. In particular, our research suggests that test sentences whose pragmatic presuppositions are unsatisfied in the experimental situation are also unlikely to provide results allowing an accurate assessment of a child's knowledge of syntactic principles. It is necessary to establish· which kinds of presuppositions children are sensitive to, and to ensure that these are satisfied in experimental tasks.
2.1. Parsing 2.1.1. Subjacency. One universal constraint which should be innate is Subjacency. Subjacency prohibits extraction of cohstituents from various constructions, including relative clauses. However, in an experimental study by Otsu (1981), many children responded as if they allowed extraction from relative clauses in answering questions about the content of pictures. For example, children saw a picture of a girl using a crayon to draw a monkey who was drinking milk through a straw. They were then asked to respond to question (1).
(1) What is Mary drawing a picture of a monkey that is drinking milk with?
Otsu found that many children responded to (1) in a way that appeared to violate Subjacency. In this case, the answer that is in apparent violation of Subjacency is "a straw." This is because "a straw" is appropriate only if the what has been moved from a position in the monkey drinking milk clause as shown in (2a), rather than from the Mary drawing picture clause as shown in (2b).
(2) a) *What is Mary drawing a picture of a monkey [that is drinking milk with _]?
b) What is Mary drawing a picture of a monkey [that is drinking milk] with_?
Competence and Perfonnance in Child Language 121
But the monkey drinking milk clause is a relative clause, and Subjacency prohibits the what from moving out of it. Thus the only acceptable structure is (2b), and the only acceptable answer is "a crayon." If these data are interpreted solely in terms of children's grammatical knowledge, then the conclusion would then have to be that knowledge of Subjacency sets in quite late in at least some children. As we noted earlier, Otsu suggested that the innateness of Subjacency could be salvaged by showing that the children who appeared to violate Subjacency had not yet mastered the phrase structure of relative clauses (of sufficient complexity to contain an extractable noun phrase). When he cOftducted an independent test of knowledge of relative clause structure, he found, as predicted, a correlation between phrase structure and Subjacency application in the children's performance. However, the children's performance was still surprisingly poor: 25% of the children who were deemed to have mastered relative clauses gave responses involving ungrammatical Subjacency violating extractions
. from relative clauses. We have argued (Crain & Fodor, 1984) for an alternative analysis of Otsu's data, which makes it possible to credit children with knowledge of both phrase structure principles and constraints on transformations from an early age. We claim that children's parsing routines can influence their performance on the kind of sentences used in the Subjacency test; in particular, that there are strong parsing pressures encouraging subjects to compute the ungrammatical analysis of such sentences. Until a child develops sufficient capacity to override these parsing pressures, they may mask his syntactic competence, making him look as if he were ignorant of Subjacency. A powerful general tendency in sentence parsing by adults is to attach an incoming phrase low in the phrase marker if possible. This has been called Right Association; see Kimball (1973), Frazier and Fodor (1978). In sentence (3), for example, the preferred analysis has with NP modifying drinking milk rather than modifying drawing a picture, even though in this case both analyses are grammatically well-formed because there has been no WH-movement. (3) Mary is drawing a picture of a monkey that is drinking milk with NP. To see how strong this parsing pressure is, note how difficult it is to get the sensible interpretation of (3) when a crayon is substituted for NP. This
Right Association preference is still present if the NP in (3) is extracted, as in (1). The word with in (1) still coheres strongly with the relative clause, rather than with the main clause. The result is that the analysis of (2) that is most immediately apparent is the ungrammatical (2a) in which what has been extracted from the relative clause. Since this 'garden path' analysis is apparent to most adults, it is hardly surprising if some of Otsu's child subjects were also tempted by it and responded to (1) in the picture verification task by saying "a straw" rather than "a crayon." We conducted several experiments designed to establish the plausibility of this claim that the relatively poor performance of children on sentences like (1) is due to parsing pressures rather than to ignorance of universal constraints. In the first experiment, we tested children and adults on complement-clause questions as in (4). Subjacency does not prohibit extraction from complement clauses, so if there were no Right Association effects this sentence should be fully ambiguous, with both interpretations equally available. (4) What is Bozo watching the dog jump through? That is, given a picture in which Bozo the clown is looking through a keyhole at a dog jumping through a hoop, it would be correct to say either the "the keyhole" or "a hoop." Intuitively, though, the interpretations are highly skewed for adults, with a strong preference for the Right Association interpretation ("hoop") in which the preposition attaches within the lower clause. Our experiment showed that the same is true for children. We tested twenty 3- to 5-year-olds (mean age 4;6) on these sentences using a picture verification task just like Otsu's, and 90% of their responses were in accord with the Right Association interpretation. 2 Thus children and adults alike are strongly swayed by Right Association. This is an important result. To the best of our knowledge the question of whether children's parsing strategies resemble those of adults has not previously been investigated. But children certainly should show the same preferences as adults, if the human sentence parsing mechanism is innately structured. And the parsing mechanism certainly should be innately structured, because it would be pointless to be born knowing a lot of facts about language if one weren't also born knowing how to use those facts for speaking and understanding. It is satisfying, then, to have shown that children
Competence and Performance in Child Language 123
reading of the pronoun in certain comprehension tasks. The results of a new comprehension methodology show that children as young as 2; admit the same range of interpretations for pronouns as adults do. Two sources of evidence have been cited as evidence that children up to 5 or 6 years uniformly reject backward pronominalization. First, children who are asked to repeat back a sentence such as (7) often respond by converting it into a forward pronominalization construction, as in (8) (Lust, 1981). (7) Because she was tired, Mommy was sleeping. (8) Because Mommy was tired, she was sleeping. The fact that these children took the trouble to exchange the pronoun and its antecedent certainly indicates that they disfavor backward pronom- inalization in their own productions. But it does not show that the backward pronominalization interpretation is not compatible with the child's grammar, as suggested by Solan (1983). To the contrary, the conversion of (7) to (8) shows that children do accept backward pronominalization in comprehension; for they would think of (8) as an acceptable variant of (7) only if they were interpreting the pronoun in (7) as coreferential with the subsequent lexical noun phrase (Lasnik & Crain, 1985). Second, it has been found that when the acting- out situation for a sentence like (6) includes a potential referent for he other than the duck (e.g., a farmer), this unmentioned object is usually favored by the children as the referent of the pronoun (Solan, 1983; Tavakolian, 1978). In contrast to the prevailing view, we would attribute this to a parsing preference for the extra- sentential interpretation of the pronoun; it does not have to be taken as evidence that children have a grammatical prohibition against backward anaphora. Our suggestion, then, is that children's knowledge might be comparable to, that of adults, even if their performance differs. It is particularly important to keep this distinction in mind for potentially ambiguous constructions such as these. When a sentence has more than one possible interpretation, the interpretation that children select can tell us which interpretation they prefer; it cannot show that others are unavailable to them. After all, adults also exhibit biases in connection with ambiguous constructions, but this does not lead us to accuse them of ignorance of alternative interpretations. To establish how much children
actually do know, we should look for the factors that might be biassing their interpretations, and also for ways of minimizing this bias so that interpretations which are less preferred but nevertheless acceptable to them have a chance of showing through. The most likely general source of bias against backward pronominalization is the fact that interpretation of the pronoun would have to be delayed until the antecedent is encountered later in the sentence. This retention of uninterpreted items may strain a child's limited working memory. There is some evidence for this speculation. Hamburger and Crain (1984) have noted that children show a tendency to interpret adjectives immediately, without waiting for the remainder of the noun phrase, even in cases where this leads them to give incorrect responses. And Clark (1971) has observed errors attributable to children's tendency to act out a clause immediately without waiting for other clauses in the sentence. The only way to interpret the pronoun immediately in a sentence like (6) is to assign it an extra-sentential referent, as children typically do. If this proposal is correct, it should be that children will accept backward pronominalization in an experimental task that presses subjects to access every interpretation they can assign to a sentence. Crain and McKee (1985) used a true/false paradigm in which subjects judge the truth value of sentences against situations acted out by the experimenter. The sentences were as in (9), where either a coreferential reading or an extra-sentential reading of the pronoun is possible. (9) When he went into the barn, the fox stole the food. On each trial, a child heard a sentence following a staged event acted out by one of two experimenters, using toy figures and props. The second experimenter manipulated a puppet, Kermit the Frog. Following each event, Kermit said what he thought had happened on that trial. The child's task was to indicate whether or not the sentence uttered by Kermit accurately described what had happened. Children were asked to feed Kermit a cookie ifhe said the right thing, that is, if what he said was what really happened. In this way, 'true' responses were encouraged in the experimental situation. But sometimes Kermit would say the wrong thing, if he wasn't paying close attention. When this happened, the child was asked to make Kermit eat a rag. (In pilot
124 Crain and Fodor
work without the rag ploy, we had found that children were reluctant to say that Kermit had said something wrong.) To test for the availability of both interpretations of an ambiguous sentence like (9), children judged it twice during the course of the experiment, once following a situation in which a fox stole some chickens from inside a barn (for the backward pronominalization interpretation), and once following a situation in which a man stole some chickens while a fox was in a barn (for the extra-sentential interpretation). Children accepted the backward anaphora reading for all the ambiguous sentences 73 of the time. The extra-sentential reading was accepted 81 of the time, but the difference was not significant. Much the same results were obtained even for the 7 youngest children, whose ages were from 2;10 to 3;4. Only two of the 62 subjects consistently rejected the backward anaphora reading. Thus most children find the backward anaphora reading acceptable, although it might not be preferred if they were forced to choose between inte.rpretations, as in previous comprehension studies. We should note that a variety of control sentences were also tested to rule out other, less interesting, explanations of the children's performance. For example, the children rejected sentence (10) following a situation in which Strawberry Shortcake did eat an ice cream, but not while she w~s outside playing. This shows that they were not simply ignoring the subordinated clauses of sentences in deciding whether to accept or reject them. (10) When she was outside playing, Strawberry Shortcake ate an ice cream. Sentences like (11) were also tested in order to establish that subjects were not merely giving positive responses to all sentences, regardless of their grammatical properties. (11) He stole the food when the fox went into the barn. The difference between (11) and the acceptable backward pronominalization in (9) is that in (11) the pronoun is in the higher clause and c- commands the fox, while in (9) the pronoun is in the subordinate clause and does not c-command the fox. (A node A in a phrase marker is said to c- command a node B if there is a route from A to B which goes up to the first branching node above A, and then down to B. Note that c-command is a structure-dependent relation.) There is a universal constraint that prohibits a pronoun from
c-commanding its antecedent. And indeed the children did reject (11) 87% of the time. Note that this positive result shows that the children have early knowledge not only of the absence of linear sequence conditions on pronominalization, but also of the existence of structural conditions such as c-command. (See also Lust, 1981, and' Goodluck, 1986.) 2.1.3. Subject/Auxiliary Inversion. Another study (Crain & Nakayama, 1987) also explored the tie between children's errors in acquisition tasks and sentence processing problems. This study was designed to test whether children give structure-dependent or structure-independent responses when they are required to transform sentences by performing Subject/Auxiliary inversion. As Chomsky (1971) pointed out, transformational rules are universally sensitive to the structural configurations in the sentences to which they apply, not just to the linear sequence of words. The procedure in this study was simply for the experimenter to preface dec1aratives like (12) with the carrier phrase "Ask Jabba if ... ," as in (13).
(12) The man who is running is bald.
(13) Ask Jabba if the man who is running is bald.
The child then had to pose the appropriate yes/no questions to J abba the Hutt, a figure from "Star Wars" who was being manipulated by one of the experimenters. Following each question, Jabba was shown a picture and would respond "yes" or "no." The sentences all contained a relative clause modifying the subject noun phrase. The correct structure-dependent transformation moves the first verb of the main clause to the front of the sentence, past the whole subject noun phrase, as in (14). An incorrect, structure-independent transformation would be as in (15), where the linearly first verb in the word string (which happens to be the verb of the relative clause) has been fronted. (14) Is the man who is running bald? (15) *Is the man who running is bald? For simple sentences with only one clause such as (16), which are more frequent in a young child's input, both versions of the transformation rule give the correct result. (16) Ask Jabba if the man is bald. (17) Is the man bald?
126 Crain and Fodor
We noted in section 1 a range of possible explanations of apparently delayed knowledge of linguistic facts. In the present case they would include the following:
- the construction does not, after all, belong to the core but is 'peripheral' and hence should be acquired late;
- children don't hear this construction until quite late in the course oflanguage development and so could not be expected to know it exists;
- the core principles in question undergo maturation and so are not accessible at early stages of acquisition;
- the experimental data are faulty and children do indeed have knowledge of this construction.
We will argue for this last alternative. And just as in the previously described studies of innate constraints, we will lay the blame for the misleading experimental data on the fact that traditional experimental paradigms do not make sufficient allowance for the limited memory and computational capacities of young children. Once again, our story is that non-linguistic immaturity can create the illusion of linguistic immaturity. 2.2.1. Relative Clauses. Children typically make more errors in understanding sentences containing relative clauses (as in 22) than sentences containing conjoined clauses (as in 23), when comprehension is assessed by a figure manipulation (act-out) task. (22) The dog pushed the sheep that jumped over the fence. (23) The dog pushed the sheep and jumped over the fence. The usual finding that (22) is more difficult for children than (23) up to age 6 years or so has been interpreted as an instance oflate emergence of the rules for subordinate syntax in language development (e.g., Tavakolian, 1981). However, though coordination may be innately favored over subordination, it is also true that subordination is ubiquitous in natural language; relative clause constructions are very close to the 'core.' So ignorance of relative clauses until age 6 would stretch the innateness hypothesis. Fortunately this is not how things stand. Hamburger and Crain (1982) showed that the source of children's performance errors on this task is not a lack of syntactic knowledge. By constructing pragmatic contexts in which the presuppositions of restrictive relative clauses were satisfied, they were able to demonstrate mastery
of relative clause structure by children as young as 3 years. There are two presuppositions in (22): (i) that there are at least two sheep in the context, and (ii) that one (but only one) of the sheep jumped over a fence prior to the utterance. The reason why previous studies failed to demonstrate early knowledge of relative clause constructions, we believe, is that they did not pay scrupulous attention to these pragmatic presuppositions. For example, subjects were required to act out the meaning of a sentence such as (22) in contexts in which only one sheep was present. The poor performance by young children in these experiments was attributed to their ignorance of the linguistic properties of relative clause constructions. But suppose that a child did know the linguistic properties, but that he also was aware of the associated presuppositions. Such a child might very well be unable to relate his correct understanding of the sentence to the inappropriate circumstances provided by the experiment. Adult subjects may be able to 'see through' the unnaturalness of an experimental task to the intentions of the experimenter, but it is not realistic to expect this of young children. Following this line of reasoning, Hamburger and Crain (1982) made the apparently minor change of adding two more sheep to the acting out situation for sentence (22), and obtained a much higher percentage of correct responses. The most frequent remaining 'error' was failure to act out the event described by the relative clause, but since felicitous usage presupposes that this event has already occurred, this is not really an error but is precisely the kind of response that is compatible with perfect- comprehension of the sentence. This interpretation of the data is supported by the fact that there was a positive correlation between incidence of this response type and age. 5 We have conducted another series of studies on relative clauses, trying several other techniques for assessing grammatical competence. In one study, we employed a picture verification paradigm to see if children could distinguish relative clauses from conjoined clauses, despite the claim of Tavakolian (1981) that they systematically impose a conjoined clause analysis on relatives. In this study, seventeen 3- and 4- year-oIds responded to relative clause constructions like (24). (24) The cat is holding hands with a man who is holding hands with a woman. (25) The cat is holding hands with a man and is holding hands with a woman.
Competence and Performance in Child Language 127
This sentence was associated with a pair of pictures, one that was appropriate to it and one that was appropriate to the superficially similar conjoined sentence (25). 8eventy percent of the 3- year-oIds' responses and 94 of the 4-year-olds' responses matched sentences with the appropriate picture rather than with the one depicting the conjoined clause interpretation. A second technique we tried used a 'silliness' judgment task (see Hsu, 1981) to establish whether children can differentiate relative clauses from conjoined clauses. Ninety-one percent of the responses of the twelve 3- and 4-year-olds tested categorized as 'silly' sentences such as (26), although sentences such as (27) were accepted as sensible 87% of the time. (26) The horse ate the hay that jumped over the fence. (27) The man watched the horse that jumped over the fence. Notice that sentence (26) would not be anomalous if the that -clause were misinterpreted as an and - clause, or if it were interpreted as extraposed from the subject NP; in both cases, the horse would be the understood subject of the relative clause. The results therefore indicate that most children interpret the that-clause in this sentence correctly, i.e., as a subordinate clause modifying the hay. Informal testing of adults suggests that the only respect in which children and adults differ on the interpretation of relative clauses is that the adults are somewhat more likely to accept the extraposed relative analysis as well, though even for adults this analysis is much less preferred. A third experiment, on the phrase structure of relative clause constructions, indicates that children, like adults, treat a noun phrase and its modifying relative clause as a single constituent, inasmuch as they can construe it as the antecedent for a pronoun such as one. In a picture verification study, fifteen 3- to 5- year-olds responded to the instructions in (28). (28) The mother frog is looking at an airplane that has a woman in it. The baby frog is looking at one too. Point to it. Ninety-three percent of the time the subjects chose the picture in which the baby frog was looking at an airplane with a woman in it, in preference to the picture in which the baby frog was looking at an airplane without a woman in it. That is, the relative clause was included in the noun phrase assigned as antecedent to the pronoun.
In short: the weight of evidence now indicates that children grasp the structure and meaning of relative clause constructions quite early in the course of language acquisition, as would be expected in view of the central position of these constructions in natural language.. 2.2.2. Temporal Terms. Another line of research has yielded support for the claim that presupposition failure is implicated in children's poor linguistic performance. These studies employed sentences containing temporal clauses with before and after, as in (29).
(29) Push the red car to me before/after you push the blue car.
Clark (1971) and Amidon and Carey (1972) have claimed that most normal, 3- to 5-year-olds do not understand these sentences appropriately. 8ince Amidon and Carey established that the children were familiar with concepts of temporal sequence (e.g., as expressed by words like first and last), the implication is that the structure of these adverbial clauses is beyond the scope of the child's grammar at this age. However, the acting-out tasks employed in these studies were once again unnatural ones which ignored the presuppositional content of the test sentences. Felicitous usage of sentence (29) demands that the pushing of the blue car has already been contextually established by the hearer as an intended, or at least probable, future event; but this was not established in these experimental tasks. It is very likely, then, that these studies underestimated children's ability to comprehend temporal subordinate clauses. For example, Amidon and Carey reported that five and six year old children who were not given any feedback frequently failed to act out the action described in the subordinate clause. Johnson (1975) found that four and five year old children correctly acted out commands such as those in (30) only 51% of the time; again, the predominant error was failure to act out the action described in the subordinate clause.
(30) a Push the car before you push the truck. (81 before 82)
b. Mter you push the motorcycle, push the bus. (After 81, 82)
c. Before you push the airplane, push the car. (Before 82, 81)
d Push the truck after you push the helicopter. (82 after 81)
Competence and Performance in Child Language 129
an unnatural experimental situation, but children, with their more limited cognitive and social skills, apparently do not have this ability. Consequently, they are highly sensitive to pragmatic infelicities. And therefore their linguistic knowledge can be accurately appraised only by tests which include controls to insure that they are not penalized by their knowledge of pragmatic principles. 2.3. Plans Another possible source of poor performance by children is in formulating the action plans which are needed in order to obey an imperative, or act out the content of a declarative sentence which they have successfully processed and understood. As we use the term, a plan is a mental representation used to guide action. A plan may be simple in structure, consisting of just a list of actions to be performed in sequence; or it may be internally complex, with loops and branches and other such structures now familiar in computer programs. Formulating a plan is a skill that makes demands on memory and computational resources. In certain experimental tasks, these demands may outweigh those of the purely linguistic processing aspects of the task. So when children perform poorly, it is important to consider the possibility that formulating, storing or executing the relevant action plan is the source of the problem, rather than imperfect knowledge of the linguistic rules or an inability to apply them in parsing the sentence at hand. 2.3.1. Prenominal Modifiers. The first study on plans that we conducted was in response to the claim by Matthei (1982) and Roeper (1972) that 4- to 6-year-olds have difficulty in interpreting phrases such as (33) containing both an ordinal and a descriptive adjective. (33) the second striped ball ?onfronted with an array such as (34), many chIldren selected item (ii), i.e., the ball which is second in the array and also is striped, rather than item (iv) which is the second of the striped balls (counting from the left as the children were trained to do).
(34) Array for "the second striped ball"
better than the younger group. What is perhaps most interesting is that the younger group appear to be even more sensitive than the older group to the proper contextual embedding ofutterances. 6 A breakdown of the types of errors that occurred reveals that the predominant errors are (i) acting out the main clause only, and (ii) reversing the correct order of the actions. As noted above for relative clause constructions, acting out the main clause only is a quite reasonable response given that the context failed to satisfy the subordinate clause presupposition. And in fact most of these errors were found in the I and NC groups.^7 Reversals were the most frequent error type in the study though they constituted only 19% of all responses. These errors may reflect a genuine lack of comprehension of either the temporal terms or the relevant syntactic structure. However no child in either the F or FI groups produced a consistent response pattern which would indicate that this was the case, so it seems more likely that these errors were due primarily just to occasional inattention. The main conclusion we draw from these results is that children, from a very young age, are indeed sensitive to the proper contextual embedding of language. Their performance is facilitated by satisfying the presuppositions of temporal subordinate clauses, and information which does not satisfy the presuppositions does not result in facilitation. A secondary conclusion is that children do construct the appropriate syntactic structure for sentences with embedded clauses. If the children in our study had failed to distinguish main from subordinate clauses (e.g., by assigning a 'flat' conjunction-type structure to the experimenter's commands), we would not expect to find the difference between the F and I groups we observed. Nor is it plausible to suggest that the children relied upon a structure-independent formula of 'old information precedes new infor~ation.' For example, for the F group, the new mformation was always in the main clause. If children were assuming that old information would be first, we would have expected relatively poor performance from the F group on sentences in which the main clause preceded the subordinate clause. In fact, no such effect was observed. In sum: once again, the linguistic knowledge of young children, when freed of interfering influences, appears to be quite advanced. Adults have the ability to set aside contextual factors in
(i) (^) (ii)
(iii) (iv) (v)
130 Crain and Fodor
Hamburger and Crain found that the children consistently responded to the second instruction by pointing to (v) rather than (iv), showing that they took the proform one to corefer with expressions like striped ball. Thus it appears that they do know the structure (35). Finally, we note two experiments by Hamburger and Crain (1987). The purpose of these experiments was to provide empirical support for our claim that response planning is an important factor in psycholinguistic tasks, independently of syntax and semantics. The first experiment attempts to show that children's ability to comprehend a phrase is inversely related to the complexity of the associated plan. For this purpose we compare phrases that are arguably equal to each other in syntactic complexity but differ in plan complexity. Examples are shown in (39), in increasing order of complexity of plans. (39) 1. John's biggest book ii. second green book Ill. second biggest book
change in method is to withhold the display while the sentence is being uttered, so that formation and execution of the plan are less likely to interfere with each other. A dramatic improvement in performance on a phrase like (33) also results from first asking the child to identify the first striped ball, which forces him to plan and execute part ofthe procedure he will later need for (33). Facilitating the procedural aspects of the task thus makes it possible for the child to reveal his mastery of the syntax and semantics of such expressions. Hamburger and Crain also found quite direct evidence that children do not assign the 'flat structure' analysis. The standard assumption in linguistics is that proforms corefer with a syntactic constituent. In the correct structure (35), the words striped and ball form a complete constituent, but in the incorrect structure (36) they do not. Thus the children should permit the proform one to corefer with striped ball only if they have the correct hierarchical structure. To find out whether they permit this coreference, they were tested on the instructions in (37), with the array in (38). (37) Point to the first striped ball; point to the second one.
The empirical finding, then, appears to be that children assign an interpretation that is not the same as an adult would assign to expressions of this kind. This difference is attributed by Matthei to children's failure to adopt the hierarchical phrase structure internal to a noun phrase that characterizes the adult grammar. This structure is shown in (35). Instead, Matthei argues that children adopt a 'flat structure' for phrases of this kind, with both the ordinal and the descriptive adjective modifying the noun directly as in (36).
JIo'P NP
DET N' DET^ N' /
ADI N' I' ADI (^) ADI N
/ ,^ I I I
ADI N (^) the second (^) slriped ball
I I
lite second striped ball
Any divergence between children's and adults' grammars poses a problem from the standpoint of language acquisition theory; namely, explaining how the child ultimately converges on the adult grammar without correction or other 'negative' feedback. Fortunately, there is no need to assume an error in the children's grammar in this case, for there is an alternative component of the language processor in which the errors might have arisen. In a series of experiments, Hamburger and Crain (1984) show that most children do assign the adult phrase structure and do understand the phrase. correctly as referring to the second of the striped balls. The difficulty that children experience arises when they attempt to derive from this interpretation a procedure for actually identifying the relevant item in the array. An analysis of the logical structure of the necessary procedure shows it to be quite complex, significantly more so than the procedure for "count the striped balls," the kind of phrase Matthei used in a pretest in an attempt to show that children were able to cope with the nonsyntactic demands of the task. This procedural account of the children's errors is supported by the sharp improvement in performance that results from three changes in method. One change is the inclusion of a pretask session in which the children handle and count homogeneous subsets of the items which are subsequently used in an array. This experience is assumed to prime some of the procedural planning required in the main experimental task. A second
(i)
,-.-,_.
(ii) (iii)
~ ~ (iv) (v)
132 Crain and Fodor
factors. This is probably because production avoids non-verbal response planning, which we have seen is a major source of difficulty in act-out comprehension tasks. It is worth noting also that
. in constructing contexts to elicit particular utterance types, we have no choice but to attend to the satisfaction of the presuppositions that are associated with the syntactic structures in question, because otherwise the subjects won't utter anything like the construction that is being targeted. In elicited production it is delicate manipulations of the communicative situation that give one control over the subject's utterances. 3.1. Relative Clauses. In section 2 we presented evidence of young children's competence with relative clauses. Further confirmation was obtained by Hamburger and Crain (1982), using an elicited production methodology. Pragmatic contexts were constructed in, which the presuppositions of restrictive relatives were satisfied. It was discovered that children as young as three reliably produce relative clauses in these contexts. A context that is uniquely felicitous for a relative clause is one which requires the speaker to identify to an observer which of two objects to perform some action on. In our experiment, the observer is blindfolded during identification of a toy, so the child cannot identify it to the observer merely by pointing to it or saying this / that one. Also, the differentiating property of the relevant toy is not one that can be encoded merely with a noun (e.g., the guard) or a prenominal adjective (e.g., the big guard) or a prepositional phrase (e.g., the guard with the gun), but involves a more complex state or action (e.g., the guard that is shooting Darth Vader). Young children reliably produce meaningful utterances with relative clauses when these felicity conditions are met. For example: (40) Jabba, please come over to point to the one that's asleep. (3;5) Point to the one that's standing up. (3;9) Point to the guy who's going to get killed. (3;9) Point to the kangaroo that's eating the strawberry ice cream. (3;11) Note that the possibility of imitation is excluded because the experimenter takes care not to use any relative clause constructions in the elicitation . situation. This technique has now been extended to younger children (as young as 2;8), and to the elicitation of a wider array of relative clause
constructions, including relatives with object gaps (e.g., the guard that Princess Leia is standing on). 3.2. Passives. Borer and Wexler (1987) have argued that A-chains, which are involved in the derivation of verbal passive constructions, are not available to children in the first few years. 8 Borer and Wexler maintain that knowledge of A-chains is innate, but becomes accessible only after the language faculty undergoes maturational change. We were not convinced, however, that this maturation hypothesis is necessitated by the facts. Rather, the facts seem to be consistent with A- chains being innate and accessible from the outset. One source of data cited in support of the maturation hypothesis is the absence of full passives in the spontaneous speech of young children. But this of course is not incontrovertible evidence that children's grammars are incapable of generating passives. Full passives are rarely observed in adults' spontaneous speech either, or in adult speech to children. But their paucity is not interpreted in this case as revealing a lack of grammatical knowledge. Instead, it is understood as due to the fact that the passive is a marked form which it is appropriate to use only in certain discourse contexts; in most contexts the active is acceptable and more natural, or a reduced passive without a by-phrase is sufficient. That is, the absence of full verbal passives in adult speech· is assumed to be a consequence of the fact that it's only in rare situations that the full passive is uniquely felicitous. But the same logic that explains why adults produce so few full passives may apply equally to children. Perhaps they too have knowledge of this construction, but do not use it except where the communicative situation is appropriate. We have tested this possibility in an experiment with thirty-two 3- and 4-year-old children. (Crain, Thornton, & Murasugi, 1987). One experimenter asked the child to pose questions to another experimenter. The pragmatic context was carefully controlled so that questions containing a full verbal passive would be fully appropriate. The following protocol illustrates the elicitation technique:
Adult See, the Incredible Hulk is hitting one of the soldiers Look over here. Darth Vader goes over and hits a soldier. So Darth Vader is also hitting one of the soldiers. Ask Kciko which one.
Child to Keiko: Which soldier is getting hit by Darth Vader?
Competence and Performance in Child Language 133
Note that the child knows what the correct answer is to his question, and that he cannot expect to elicit this answer from his interlocutor (Keiko) unless he includes the by-phrase. In fact, exactly 50% of responses were passives with full by -phrases). Of course, active constructions are also felicitous in this context (e.g., Which soldier is Darth Vader hitting?), even though the contextual contrast with another agent (the Incredible Hulk) may tend to favor the passive stylistically. And indeed 31% of responses were active questions with object gaps. The other 19% of responses included mostly sentences that were grammatical but not as specific as the context demanded (e.g., passive lacking by-phrases). Using this technique, we were able to elicit full verbal passives from all but three of the thirty-two children tested so far, including ones as young as 3;4. Some examples are shown in (41).
(41) She got knocked down by the Smurfie. (3;4)
Which girl is pushing, getting pushed by a car? (3;8) He got picked up from her. (3;11) It's getting ate up from Luke Skywalker. (4;0) Which giraffe gets huggen by Grover? (4;9) Note that these utterances contain a variety of morphological and other errors, but they all nevertheless exhibit the essential passive structure (underlying subject in pre-verbal position; agent in post-verbal prepositional phrase). 9 It might be argued that the children's passives elicited in this experiment do not involve true A-chains. However, since they are just like adult passives (disregarding morphological errors), the burden of proof falls on anyone who holds that adult passives involve A-chains and children's passives do not. No criterion has been proposed, as far as we know, which distinguishes adult's and children's passives in this respect. For example, it is true that the children almost always use a form of get in place of the passive auxiliary be, but get is acceptable in adult passives also. Wet is more regular and phonologically more prominent than forms of be, and this may be why it is more salient for children.) Children's considerable success in producing passive sentences appropriate to the circumstances (i.e., their correct pairing of sentence forms and meanings) constitutes compelling evidence of their grammatical competence with this construction. Comparison of these results with the results of testing the same children with two comprehension paradigms (act-
out and picture-verification) confirms that, like spontaneous production data, these measures underestimate children's linguistic knowledge. The finding that young children evince mastery of the passive obviates the need to appeal to maturation to account for its absence in early child language. Maturation cannot of course be absolutely excluded; but a maturation account is motivated only where a construction is acquired surprisingly late-where this means later than would be expected on the basis of processing complexity, pragmatic usefulness in children's discourse, and so forth. (Also, as noted in section 1, some important cross-language and cross- construction correlations need to be established to confirm a maturational approach; see Borer & Wexler, 1987, on comparison of English passives with passive and causative constructions in Hebrew.) The elicited production results suggest that the age at which passive is acquired in English falls well within a time span that is compatible with these other factors, and so maturation does not need to be invoked. 3.3. Wanna contraction. Another phenomenon that can be shown by elicitation to appear quite early in acquisition is wanna contraction in English. The facts are shown in (42) and (43).
(42)a. Who do you want to help? b. Who do you wanna help? (43)a. Who do you want to help you? b. Who do you wanna help you?
Every adult is (implicitly) aware that contraction is admissible in (42b) but not (43b). However, on the usual assumption that children do not have access to 'negative data' (Le., are not informed of which sentences are ungrammatical) it is difficult to see how this knowledge about the ungrammaticality of sentences like (43b) could be acquired from experience (at any age). So this is yet another candidate for innate linguistic knowledge. (What is known innately would be that a trace between two words prevents them from contracting together. The relevant difference between (42b) and (43b) is that in (43b) the who is the subject of the subordinate clause and has been moved from a position between the want and the to. The trace of this noun phrase that is left behind blocks the contraction. In (42b), by contrast, the trace is in object position after help, and therefore is not in the way of the contraction.) Crain and Thornton (in press) used the elicited production technique to encourage children to ask questions that would reveal violations like (43b) if
Competence and Performance in Child Language 135
Frazier, L., &; Fodor, J. D. (1978). The sausage machine: A new two-stage parsing model. Cognition, 6, 291-325. Goodluck, H. (1986). Children's interpretation of pronouns and null NPs: Structure and strategy. In P. Fletcher &; M. Garman (Eds.), umguage acquisition: Studies in first langUllge deoelopment (2nd ed.). Cambridge, MA: Cambridge University Press. Goodluck, H., &; Tavakolian, S. (1982). Competence and processing in children's grammar of relative clauses. Cognition, 8,389-416. Gorrell, P., Crain, S., &; Fodor, J. D. (1989). Contextual information and temporal terms. Journal of Child Language, 16,623-632. Hamburger, H., &; Crain, S: (1982). Relative acqUisition. In S. Kuczaj (Ed.), Language deoelopment (Volume II, pp. 245-274). Hillsdale, NJ: Lawrence Erlbaum Associates. Hamburger, H., &; Crain, S. (1984). Acquisition of cognitive compiling. Cognition, 17, 85-136. Hamburger, H., &; Crain, S. (1987). Plans and semantics in human processing of language. Cognititle Science, 11, 101-136. Hsu, J. R. (1981). The deoelopment of structural principles related to complement subject interpretation. Doctoral dissertation, The City University of New York. Jakubowicz, C. (1984). On markedness and binding principles. Proceedings of the Northeastern Linguistic Society, Amherst, Massachusetts. Johnson, H. (1975). The meaning of before and after for preschool children. Journal of Experimental Child Psychology, 19. Kimball, J. (1973). Seven principles of surface structure parsing in natural language. Cognition, 2, 15-47. Lasnik, H., &; Crain, S. (1985). On the acquisition of pronominal reference. Lingua, 65,135-154. Lust, B. (1981). Constraint on anaphora in child language: A prediction for a universal. In S. Tavakolian (Ed.), Language acquisition'and linguistic tht!Dry (pp. 74-96). Cambridge, MA: MIT Press. Matthei, E. M. (1981). Children's interpretations of sentences containing reciprocals. In S. Tavakolian (Ed.), Language acquisition and linguistic theory (pp. 97-115). Cambridge, MA: MIT Press. Matthei, E. M. (1982). The acquisition of prenominal modifier sequences. Cognition, 11, 301-332. Nakayama, M. (1987). Performance factors in subject-aux inversion by children. Journal of Child Language, 14, 113-125. Otsu, Y. (1981). Uniuersal grammar and syntactic deuelopment in children: Toward a theory of syntactic deoelopment. Unpublished doctoral dissertation, M.l.T. Phinney, M. (1981) The acquisition of embedded sentences and the NIC. Proceedings of the North Eastern Linguistic Society, 11. Amherst: University of Massachusetts Richards, M. M. (1976). Come and go reconsidered: Children's use of deictic verbs in contrived situations. Journal of Verbal Learning and Verbal Behauior, 15, 655-665. Roeper, T. W. (1972). Approaches to a theory of language acquisition with examples from German children. Unpublished doctoral dissertation, Harvard University. Roeper, T. W. (1986). How children acquire bound variables. In B. Lust (Ed.), Studies in the acquisition of anaphora, Volume I. Dordrecht, Holland: D. Reidel Publishing Company. Solan, L. (1983). Pronominal reference: Child language and the theory of grammar. Dordrecht, Holland: D. Reidel Publishing Company. Solan, L., &; Roeper, T. W. (1978). Children's use of syntactic structure in interpreting relative clauses. In H. Goodluck &; L. Solan (Eds.), Papers in the Structure and Deuelopment of Child
Language. UMASS Occasional Papers in Linguistics (Vol. 4, pp. 105-126). Tavakolian, S. L. (1978). Children's comprehension of pronominal subjects and missing subjects in complicated sentences. In H. Goodluck &; L. Solan (Eds.), Papers in the Structure and Deuelopment of Child Language. UMASS Occasional Papers in Linguistics (Vol. 4, pp. 145-152). Tavakolian, S. L. (1981). The conjoined-clause analysis of relative clauses. In S. Tavakolian (Ed.), Language acquisition and linguistic theory (pp. 167-187). Cambridge, MA: MIT Press,. de Villiers, J. G., &; de Villiers, P. A. (1986). The acquisition of English. In D. Slobin (Ed.), The crosslinguistic study of language acquisition Volume I: The dJlta. Hillsdale, NJ: Lawrence Erlbaum Associates. Wexler, K"^ &;^ Chien,^ Y.^ (1985) The^ development^ of lexical anaphors and pronouns. Papers and Reports on Chl7d Language Deuelopment. Stanford, CA: Stanford University.
FOOTNOTES
·Language and cognition: A deoelopmental perspectiue (in press). Norwood, NJ: Ablex. tAlso University of Connecticut, Storrs. ttAlso Graduate Center, City University of New York. lSusan Carey has pointed out (Boston University Conference,
- that the linguistic maturation hypothesis predicts that knowledge of a linguistic principle should correlate with gestation age rather than with birth age in children born prematurely. Unfortunately, variability is probably such that no clear correlation could be expected to show itself by age 4 or 5, when passiVes and other relevant syntactic constructions are claimed to emerge. 2For full details of procedure and results of this experiment, and of all other studies reported in this paper, we refer readers to the original pu blications. 3As far as is known at present, no natural language exhibits this blanket prohibition against backward pronominalization; see discussion in Lasnik and Crain (1985). This suggests that it is not a possible constraint in a natural language grammar, in which case it should not be entertained by children at any age or stage of acquisition (unless one assumes linguistic maturation). 4The awkwardness of the prosodic contour for (18), with its heavy juncture before the final word, may indicate that this kind of construction is also an unnatural one for the sentence production routines. SIn reViewing the literature on relative clauses, de Villiers and de Villiers (1986) suggest that if earlier work had counted the assertion-only response as correct, children would have been seen to perform better there too. This objection is unwarranted, for two reasons. First, responses of this type did not appear in other studies, presumably because these studies failed to meet the presuppositions of the restrictive relative clause. More important, in the Hamburger and Crain study this response was not evinced by any of the 3-year-old children, and accounted for only 13% of the responses of the 4-year-olds. Nevertheless, even the 3-year-olds acted out sentences with relative clauses at a much higher rate (69%) of success than in earlier studies. 6These results should be interpreted with caution due to the small and unequal number of subjects in each SUbgroup leading to rather uneven data. For example, the older F group performed relatively poorly compared to the younger F group,
136 Crain^ and^ Fodor
though closer analysis reveals that this is due to the poor performance of just one child (4;4) in the F group. 7There were no main-clause-only errors in the Fl grol;lP' For the F group, 12 of the 16 main-clause-only errors (out of 168 responses) are due to one child 8 An A-chain is the association of a trace with a moved noun phrase in an A-pOSition (= argument position such as Subject). For example, in The bagel was ellten by Bill there is an A-chain consisting of the bagel and its associated trace after eaten.
9The proper reversal of underlying subject and object order occurred even when the task was complicated by an implausible scene to be described. For example, the sentence One dinoSllur's being eated from the ice cream cone was used to describe a situation in which the dinosaur was indeed being eaten by the ice cream, not vice versa. lOIn preliminary evaluation of the audio tapes, we have found it unexpectedly easy to distinguish children's contracted and non-contracted forms in most cases.
