learning names for solid substances: quantifying solid entities in terms of portions

Cognitive Development, 8, 83-104 (1993)

Learning Names for Solid Substances: Quantifying Solid Entities

in Terms of Portions

Sandeep Prasada Massachusetts Institute of Technology

Objects are quantified in terms of individuals whereas substances are quantified in terms of portions. Soja, Carey, & Spelke (1991) have shown that 2-year-olds take words used to name solid entities as naming objects and quantify them in terms of individuals. One consequence of children's bias to quantify solids in terms of individuals is that they may have problems learning names for solid substances. Previous research suggests that this may be the case. In the study presented here, two experiments investigated 2½- to 3~A-year-olds ' knowledge of names for solid substances, their ability to learn names for solid substances, and their knowledge of nonlinguistic properties of solid substances. It was found that children of this age do not know many names for solid substances but can be taught names for them. There was also evidence that children represent the names as mass nouns and possibly adjectives. Finally, it was found that there is development of children's nonlinguistic knowledge of substances between the ages of 21,6 and 3 years. The relevance of these results for theories of lexical development are discussed.

The ontological categories OBJECT and SUBSTANCE play an important role in many theories of the acquisit ion of c o u n t - m a s s noun syntax (Bloom, 1990; Gordon , 1985; Macnamara , 1982; McPherson, 1991) and lexical development (Soja, Carey, & Spelke, 1991). The interest in objects and substances derives from the different manne r in which one quantifies these entities. Objects such as tables and dogs are quantif ied in terms of atomic individuals , whereas substances such as sand and wood are quantif ied in terms of portions (Bloom, in press; Macnamara , 1986; McPherson, 1991). Categories such as TABLE and DOG pro-

This research was supported by NIH Training Grant T32-MH 18823 and by a fellowship funded by a grant from the Fairchild Foundation to MIT. I would like to thank Susan Carey for her insightful comments and advice at various stages of the study and comments on drafts of the article. 1 would also like to thank Paul Bloom, Geoff Hall, John J. Kim, Laura Klatt, Nancy Soja, Sandra Waxman, and two anonymous reviewers for comments on earlier versions. 1 am grateful to the children, teachers, and parents at the Bright Horizons, Lotus, and Peabody Terrace day-care centers, and the Cambridge Montesorri School.

Correspondence and requests for reprints should be sent to Sandeep Prasada, Institute for Re- search in Cognitive Science, 3401 Walnut St. Room 408C, University of Pennsylvania, Philadelphia, PA 19104-6228.

Manuscript received February 27, 1992; revision accepted October 22, 1992 83

84 Sandeep Prasada

vide a principle of individuatibn which specifies what is to count as one instance of a table or dog (Macnamara, 1986). Categories such as SAND and WOOD, on the other hand, do not provide a way to specify what is to count as one instance of sand or wood; sand and wood are quantified in terms of portions (e.g., a pile of sand, a piece of wood; Macnamara, 1986).

The different manner in which one quantifies objects and substances is en- coded in languages like English in the distinction between count nouns and mass nouns. Count nouns quantify in terms of individuals, thus names for objects are lexicalized as count nouns. Mass nouns quantify in terms of portions, therefore names for substances are lexicalized as mass nouns. The count-mass noun distinction extends to nouns such as par~, and justice which are not names for objects or substances. Children must have a way to learn nouns such as these that do not name objects or substances. A number of researchers have suggested that children use the quantificational properties of objects and substances to learn the quantificational properties of determiners (e.g., a, another, 0 ) and locutions with specific quantificational properties (e.g., a bunch of, a piece of) and then use this information to learn new count and mass nouns (Bloom, in press; Gordon, 1985; McPherson, 1991).

These theories of the acquisition of count-mass syntax assume that the categories OBJECT and SUBSTANCE are available to children and that children quantify the category OBJECT in terms of individuals and the category SUBSTANCE in terms of portions. Quine (1960), on the other hand, suggests that children may not have these categories or know the quantificational properties of these categories ini- tially. Quine suggests that the categories, as well as their quantificational properties, are learned through language. He does not, however, specify how the child may learn the count-mass syntax of a language that would, in turn, help the child learn categories and their quantificational properties.

Soja, Carey, and Spelke (1991) provide evidence against Quine's proposals by showing that 2-year-olds who have not yet mastered count-mass noun syntax represent the categories OBJECT and NONSOLID SUBSTANCE and know the quantificational properties of these categories. On the basis of their data, Soja et al. suggest that children use the following procedures to help constrain word meanings and learn the quantificational properties of nouns:

Procedure 1 Step 1: Test to see if the speaker could be talking about a solid object; if yes, Step 2: Conclude the word refers to individual whole objects of the same

type as the referent.

Procedure 2 Step 1: Test to see if the speaker could be talking about a nonsolid substance;

if yes, Step 2: Conclude the word refers to portions of the substance of the same

type as the referent. (Soja et al., 1991, pp. 182-83)

Names for Solid Substances 85

One possible consequence of children's use of a procedure like Procedure 1 is that children will have difficulties in learning names for solid substances (e.g., wood; Bloom, in press; Dickinson, 1988; Soja, 1987, 1991). Children typically encounter solid substances in the form of objects. Given the evidence that they are biased towards conceptualizing solid entities as objects which are quantified in terms of individuals, it is possible that young children may not be able to conceptualize solid entities as portions of stuff and thus may be unable to learn names for solid substances. There is some evidence that suggests that young children have problems learning names for solid substances. Children younger than 3~/2 years of age produce (Soja, 1987, 1991) and comprehend (Dickinson, 1986) very few, if any, names for solid substances. Furthermore, Dickinson (1988) was unable to teach 3-year-olds names for novel solid substances. The youngest age at which children have been shown to map words onto kind of solid substance is 3t/2 years (Au & Markman, 1987).

If children do use some words to refer to solid substances, it is important to determine whether the words are represented as mass nouns or as adjectives. Adults usually know words for kinds of solid substances which they lexicalize as mass nouns (e.g., This table is made of wood), as well as property names which they lexicalize as adjectives (e.g., This is a wooden table). Whereas one might expect Procedure 1 to interfere with the acquisition of mass nouns because they quantify in terms of portions, the procedure should not interfere with the acquisition of adjectives which are not quantified in any way. If children learn words for solid substances as adjectives, they will name some property or combination of properties of an object that is related to the kind of solid substance that the object is made of (e.g., hard and brown and smooth) rather than the kind of stuff.

Previous research on children's learning of names for solid and nonsolid substances does not provide evidence regarding whether children are mapping the words onto substance or some property of the substance. In all these experiments, children were interpreted as mapping the word onto substance if they picked the item(s) in the response set which matched the teaching object on substance rather than kind of object (Markman & Wachtel, 1988), or shape (Soja et al., 1991), or shape or color (Au & Markman, 1987). Whereas it is possible that children were mapping the words onto substance, it is also possible that children were naming the texture or some combination of properties of the substance. The study presented here investigated the question of what children are mapping names for solid substances onto by looking to see if children used these words to respond to questions that require a substance reply and if children use the words with the locution made of which requires a substance response when followed by a nonplural noun. The study also used production data to investigate whether children represent the words as mass nouns or as adjectives.

The quantificational properties of solid substances are relevant for how words for solid substances are lexicalized, but there are many properties of solid sub-

86 Sandeep Prasada

stances that are independent of the manner in which one quantifies solid substances. For example, whether or not one can squeeze a piece of sponge is not in any way dependent on whether sponge is quantified over individuals or portions. This suggests that although the existence of Procedure 1 may interfere with children's acquisition of names for solid substances, it should not interfere with those inferences involving solid substances which do not require the quantificational properties of solid substances. There is some evidence that suggests that this is the case. Soja (1991) found that 21/2-year-old girls and 3V2-year-old boys and girls base their inferences about the smell of an object on the basis of the kind of substance the object is made of. Schmidt (1987) found that 3-year-olds base their inferences about the smell and weight of objects on the basis of substance kind. Soja (1987) also found that 3-year-olds base inferences about the weight of an object on the object's substance kind rather than object kind.

Taken together, the studies on children's acquisition of names for solid substances and children's nonlinguistic inferences about solid substances suggest that kind of solid substance is available as the basis of nonlinguistic inferences, but is unavailable as a possible word meaning to the young child. If this asymmetry between children's ability to use kind of solid substance as the basis of nonlinguistic inductions and children's ability to learn names for solid substances is in fact real, it presents strong evidence for distinct semantic and conceptual constraints on word meanings. The asymmetry would also provide additional evidence for Soja et al.'s (1991) Procedure 1. Finally, the asymmetry would suggest that the ontological categories that are available for guiding language acquisition do not include SUBSTANCe, and that the relevant category may be NONSOLID SUBSTANCE.

This study investigated whether or not there is an asymmetry in children's ability to learn names for solid substances and their ability to use solid substances as the basis of nonlinguistic inductions. The study also sought to determine whether children are mapping names for solid substances onto kind of solid substance, or if the words are being mapped onto some property of the substance (e.g., color or texture) or a combination of properties (e.g., hard and rough and brown). If children are mapping the words onto kind of substance, they should represent the words as mass nouns. If, on the other hand, children are learning the words as property names, they should represent the words as adjectives.

In Experiment 1, a word-learning task was used to investigate whether 21/2 - to 3V2-year-olds can learn names for solid substances. An elicitation task was used to investigate which solid substance words children of this age know, whether they represent the words as nouns or adjectives, and children's knowledge of properties of solid substances. In Experiment 2, a nonlinguistic induction task investigated children's knowledge of properties of objects that are related to the kind of solid substance the objects were made of.


EXPERIMENT 1

In order to test the reality of the asymmetry between children's ability to learn names for solid substances and their ability to use solid substance as the basis of nonlinguistic inductions one can (a) question the validity of the studies that suggest that solid substances are available as the basis of nonlinguistic inductions, or (b) question the validity of the studies which suggest that children younger than 3½ years of age cannot learn names for solid substances. This experiment questions the latter result because it is a negative result and there are reasons to believe that the negative result may be due to methodological factors.

In this experiment, children were taught names for solid substances using familiar objects and a large variety of substances. The substance words were used as mass nouns with the locution made of and as adjectives. Half of the substances used in the experiment had a different color in the teaching situation and the response set in order to test for the possibility that children were mapping the substance names onto color rather than substance.

In addition to the word-learning task, an elicitation task was run to investigate the following questions: (a) Which solid substance names do 2½- to 3½-year- olds know, (b) Do the words actually refer to substances, and (c) Are the words represented as mass nouns or adjectives? In the task, children were asked to name various objects, the color and shape of the objects, and the kind of substance the objects were made of. Solid substance names were elicited in two ways; first, children were asked what various objects were made of and, sec- ondly, children were asked to explain a salient difference in a substance-related property between two objects (e.g., why one can squeeze one (sponge) ball but not another (wooden) ball). Note that this question does not force the child to respond with a substance name. They could answer the question by making reference to any property of one of the objects including the object's size, color, or texture. The explanations may also provide evidence regarding whether children are representing the solid substance words as mass nouns or adjectives. Responses using the locution made of (e.g., Because it's made of metal) would provide evidence that the name for the substance is represented as a mass noun. Responses that lack a determiner (e.g., Because it's metal) are consistent with a mass noun or an adjective representation and responses in which the substance word precedes a noun (e.g., Because it's a metal ball) would suggest that the word is represented as an adjective. Finally, the explanations provide a measure of children's nonlinguistic knowledge of solid substances; specifically, that certain (substance-related) properties of objects are due to the substance of which the object is made.

Method Subjects. Thirty-two children from day-care centers in the Cambridge-

Boston area participated. They were divided into a younger group ranging in age

88 Sandeep Prasada

Table 1. Objects, Substances, and Substance-Related Property Differences Used in the Elicitation Task

Object Substance I Substance 2 Property

ball wood sponge squeezability plate plastic paper foldability tube metal rubber bendability duck cloth playdoh scratchability bowl glass clay transparency tile styrofoam slate weight

from 2;4 to 3;0 (M age = 2;9) and an older group ranging in age from 3;I to 3;7 (M age = 3.4).

Materials. Six types of objects were used in the elicitation task. Each type of object was made out of two different substances that have a salient property difference (e .g . , can squeeze a sponge ball but not a wooden ball). The objects, substances, and salient property differences are given in Table 1. The same objects were used in the teaching set of the word-learning task. In addition to these objects, the response set in the word-learning task included six objects of the same kind as in the teaching set but made of a third substance (e.g. , plastic ball) and six pairs of objects made of the same kinds of substances as the objects in the teaching set (e .g. , a sponge doll and a wooden doll). The objects and substances used in the word-learning task are given in Table 2.

Table 2. Stimuli Used in the Word-Learning Task in Experiment 1 and the Nonlinguistic Inference Task in Experiment 2

Objects and Substances Used in the Word-Learning Task in Experiment 1

Teaching Object Response Set

wood/sponge ball paper/plastic plate cloth/playdoh duck clay/glass bowl slate/styrofoam tile metal/rubber tube

wooden doll, sponge doll, plastic ball paper box, plastic box, rattan plate cloth heart, playdoh heart, wooden duck clay pot, glass jar, plastic bowl slate star, styrofoam star, cork tile metal socket cover, rubber socket cover, cardboard tube

Objects, Substances, and Properties Used in the Nonlinguistic Inference Task in Experiment 2

Teaching Object Response Set Property

sponge ball wooden doll, sponge doll. tennis ball squeezability paper plate paper box, plastic box, rattan plate foldability playdoh duck cloth heart, playdoh heart, wooden duck scratchability glass bowl clay pot, glass jar, plastic bowl transparency styrofoam tile slate star, styrofoam star, cork tile weight rubber tube metal socket cover, rubber socket cover, cardboard tube bendability


Teaching Object

@ Response Sot

@ Figure I. Example of stimuli used in the word-learning task.

Procedure. Each child was taught the name for one of the substances of each of the six pairs of objects used as the teaching stimuli (see Table 2). On a given trial, a Cookie Monster puppet presented the child with one of the teaching objects and asked the child what the object is called. If the child didn't know what the object was called the puppet told the child the name for the object. The puppet then told the child what the object was made of using a locution of the following form: This ball is made of sponge; This is a sponge ball. The child was asked to repeat the substance name (Can you say sponge?) to ensure that the child had heard the word properly and was paying attention. The object was put away and a response set containing the following items was brought out: (a) another object of the same kind (e.g., a plastic ball), (b) a different kind of object made of the same substance (e.g., a sponge doll), and (c) a different kind of object made of a third substance but of the same kind as (b) (e.g., a wooden doll). The child was then asked to give Cookie Monster the object that was made of the substance just taught (e.g., Give Cookie Monster the thing that is made of sponge). The third object in the response set (different from the teaching object in both kind of object and substance) was included to insure that children were not making their choices on the basis of novelty or a preference for object type. This object served as the correct response for subjects who were taught the substance name of the second object in each teaching pair. The use of the same object as both the correct and incorrect response across subjects controlled for any biases

90 Sandeep Prasada

that children may have had for picking objects from the response set. The objects and substances used in a sample trial are shown in Figure 1.

In the elicitation task, children were introduced to the Cookie Monster puppet and asked to play a game with him. A blindfold was placed on Cookie Monster and it was explained that Cookie Monster would not be able to see and so the child would have to help Cookie Monster find out what was in front of him. On a given trial, the child was presented with one pair of objects of the same kind but made of different kinds of substance (e.g., a sponge ball and a wooden ball). The child was then asked to name the objects, their color, shape, t and substance. The experimenter then summarized this information in random order and brought a salient difference in substance properties to the child's attention (e.g., can squeeze the sponge ball but not the wooden one). The child was then asked to give an explanation for this difference between the two objects. The sessions were tape recorded and children's utterances were transcribed.

Each child participated in both the elicitation and the word-learning task on separate days. The order of the tasks was counter balanced across children within each age group.

Results

Word-Learning Task. To assess whether children had learned a substance name in the word-learning task, only the trials that taught a substance name not already known by the child were analyzed. Children were counted as knowing a substance name if they correctly identified it in the elicitation task. ~ Excluding these trials ensured that the analyses included only those substances for which children did not know names.

A 2 × 2 analysis of variance (ANOVA) with age and order of task as the independent variables and proportion of correct responses as the dependent variable was carried out to see if there was development in children's ability to learn names for substances between the ages of 2V2 and 3V2 years, and to see if participating in the elicitation task first may have helped children in the word- learning task by focusing them in on substances. No effects of age or order of task were found. The percentage of trials on which children responded by picking the correct substance, made object-bias errors (picking the object that matched the teaching object on kind of object), and picked the object that did not

IThe question about the shape of the object was omitted for the trial with the duck. 2Note that this is an extremely liberal measure of children's prior knowledge of substance names

because it credits children with knowing a substance name if they used it correctly in one instance even if they might have used the word incorrectly on other trials in the elicitation task. Furthermore, half the children participated in the elicitation task after the word-learning task and thus may have learned the name in the word-learning task. It is also unlikely that children may have comprehended some of the substance names that they did not produce because Dickinson's (1986) results show that 3-year-olds' comprehension of even very common substance names like wood, glass, and plastic is poor.


100

8O

¢ o

o

~ 4(1

n

20

[ ] Older • Younger

0 Substance Object-bias error Other error

Type of Response

Figure 2. Percentage of responses that matched the teaching objects' substance kind, object kind, or neither.

match the teaching object on kind of object or substance (other errors) are shown in Figure 2.

Overall, children picked the object that matched the teaching object in substance in the response set on 65% of trials, made object-bias errors on 24% of trials, and made other errors on 11% of the trials. The proportion of correct responses is significantly greater than would be expected by chance (33%), t(31) = 6.95, p < .0001. It may be argued, however, that children had no reason to pick the object that didn't match the teaching object on object or substance kind and thus chance performance should be taken to be 50% rather than 33%. Even with this conservative estimate of chance, children made the substance interpretation more often than would be predicted by chance t(31) = 3.39, p < .002. The pattern of results for individual children was similar to the overall results in that 12 of the 16 younger children were correct on at least 67% of trials (at least 4 out of 6 trials for children who didn't know any of the words) and 9 out of 16 of the older children responded correctly on at least 67% of the trials.

Because playdoh is not a solid substance, a parallel set of analyses was carded out excluding the results of the playdoh trials. The results were virtually identical with no difference being found between the younger children's performance (64% correct) and that of the older children (66% correct); nor was there an effect of order of task. As before, the percentage of correct responses was greater than

92 Sandeep Prasada

Table 3. Responses in the Word-Learning and Elicitation Tasks by Substance

Substance

Percentage of Correct Responses

in Word-Learning Task

Percentage of Correct Identifications

in Elicitation Task

clay 46 13 cloth 64* 9 glass 67* 31 metal 73* 3 paper 67* 41 plastic 44 0 playdoh 80* 75 rubber 83* 9 slate 44 0 sponge 83* 16 styrofoam 75* 6 wood 67* 25

*Significantly greater than chance (33%), p < .05.

would be expected by chance (33%), t(31) = 6.73, p < .0001; chance (50%), t(31) = 3.22, p < .003. The pattern of responses given by the individual children was similar to the pattern found in the analysis including playdoh as well as the overall pattern; 11 out of 16 younger children responded correctly on at least 67% of the trials and 9 out of the 16 older children responded correctly on at least 67% of the trials. The percentage of correct mappings for each substance is shown in column one of Table 3. Children were successful in learning the names of most of the substances; clay, plastic, and slate seemed not to be learned as well and elicited a large number of object-bias errors.

A 2 x 2 ANOVA with age and whether the color of the substance was the same in the teaching object and the response set as the independent variables, and the proportion of correct responses as the dependent variable, was carried out to see if children were mapping the names onto color. No significant effects were found indicating that children were not mapping the names onto color.

A parallel set of analyses was carried out using data from all the trials rather than only the trials that taught substance names not already known by the children. The pattern of results was the same except that there was a higher success rate. This is presumably due to the analyses including data about words that children already knew.

Finally, an analysis was done to see if there was a relationship between the number of substance names a child already knew (produced) and the child 's ability to learn other names for solid substances. The correlation was not significant (r = .12) indicating that children who knew more names for solid substances were not better at learning new names for solid substances than children who knew fewer names for solid substances.


Elicitation Task. The responses of most interest in the elicitation task are those to the substance identification question, What is this made of?., and the explanations for substance-relevant property differences between objects (e.g., why one can squeeze a sponge ball but not a wooden one).

Substance Identification. Children responded to the question, What is this made of?. with a substance name on 52% of the trials, gave no response on 29% of the trials and a nonsubstance word on 19% of trials. Of the trials on which children responded with a substance name, 50% of the responses mentioned the correct substance. It is likely, however, that this analysis overestimates children's knowledge of names for solid substances because children could accidentally respond with the correct substance name if they knew that the question What is this made of?. requires an answer that included certain words (substance names). Carey and Bartlett (1978) found that children respond to the question What color is this? with color terms before they know the meaning of the individual color terms and Wynn (1990) has found a similar phenomenon with respect to children's early use of number words in response to the question, How many Xs are there?

A second, more conservative analysis of children's responses was carded out in which children were credited with knowledge of a substance name if they used it to refer to only the correct substance. Using this criterion, children correctly answered the substance identification question on 19% of all the trials. The percentage of correct identifications for each of the substances is given in column two of Table 3. Note that this is an extremely conservative measure of children's knowledge of names for solid substances because it requires the child to know the correct extension of the word; any confusion over the extension counts as the child not knowing the word. Furthermore, a number of the incorrect responses may be due to the task demand of answering the question. A 2 x 2 ANOVA with age and order of task as the independent variables and number of correct substance identifications as the dependent variable was carried out. A significant effect of age was found with the older children providing more correct identifications than the younger children, F(I, 28) = 6.162, p < .02.

Explanations. Children's explanations of differences in substance-relevant properties of objects (e.g., why one can squeeze a sponge ball but not a wooden one) are analyzed in this section. Children made some kind of response on 50% of the trials. Explanations were coded as relevant or irrelevant to the question. Relevant explanations were those that included (a) a substance name (e.g., It's metal, it's made of metal), (b) the texture of the object (when relevant) but no substance name (e.g., It's soft), and (c) the locution made of without any substance name. Relevant explanations accounted for the majority (72%) of the responses, incorrect possible explanations (e.g., size as an explanation for difference in weight even though the size of the two objects is the same) accounted for 6% of the responses, and irrelevant explanations (e.g., because can roll it a s

an explanation for squeezability) accounted for the remaining 22% of the r e -

94 5andeep Prasada

sponses. Of the relevant explanations, 79% referred to a solid substance, 16% referred to a texture but no substance, and 5% used the locution made of without a substance name. Many of the explanations that mentioned a substance mentioned the wrong substance. A 2 x 2 ANOVA with age and order of task as the independent variables and the number of relevant explanations as the dependent variable found a significant effect of age with older children producing more relevant explanations, F(1, 28) = 4.239, p < .05. All other effects were not significant.

Finally, the explanations that mentioned a solid substance were analyzed to see if they provide evidence regarding whether children represent solid substance terms as mass nouns or adjectives (children never used the substance names with count-noun syntax). Of these explanations, 39% of the uses of solid substance terms occurred in mass-noun contexts (made of X (where X is not marked as plural)), 61% occurred in contexts that are ambiguous between mass nouns and adjectives (it's X), and 0% occurred in adjective contexts (It's a X ball). If children were learning these words as adjectives one would expect at least some prenominal uses such as It's a metal ball. Bloom (I 970), B owerman (1973), and Brown (1973) all report that prenominal adjectives appear in the vocabularies of English speaking children at an earlier age than predicative adjectives. More importantly, for the purposes of this study, Nelson (1976) found that prenominal adjectives are more frequent than predicative adjectives in the vocabulary of 2V2- year-olds. The lack of any utterances that use substance names in prenominal position in this study strongly suggests that names for solid substances are learned as mass nouns rather than as adjectives.

Discussion The results of the word-learning task show that children as young as 2t/2 years of age can learn names for solid substances. This finding conflicts with Dickinson's (1988) finding that 3-year-olds do not map words onto kind of solid substance. Dickinson (1988) presented children with unfamiliar objects made out of novel solid substances and chunks of the substances. The object/chunks were named in a neutral condition (e.g., This is the blicket), a count-noun condition (e.g., This is a blicket), and an informative condition (This is made of blicket). He found that 3-year-olds do not map the novel word onto a material-kind interpretation in any of the conditions.

One problem with interpreting Dickinson's (1988) results as showing an inability to learn names for solid substances is that the objects used in the study were unfamiliar to the children. There is now a large body of evidence suggesting that there is a strong object bias in word learning when unfamiliar objects (i.e., objects for which children do not have a name) are used (Gelman & Taylor, 1984; Hall, 1990; Markman & Wachtel, 1988; Soja et al., 1991; Taylor & Gelman, 1988). Markman and Wachtel (1988) have shown that older children (M age = 4;0) will map a novel word onto solid substance if a familiar object is used


but will name the kind of object if an unfamiliar object is used. The 2V2-year- olds' success in the current study suggests that the unfamiliarity of the objects used by Dickinson (1988) may have been a major reason why 3-year-olds were unable to map novel words onto a substance-kind interpretation in his study. A second problem with Dickinson's (1988) study is that he used novel words and children may have known some solid substance names such as plastic, metal, and wood and thus been reluctant to take a novel word as having the same meaning due to a Principle of Contrast (Clark, 1987). Finally, many of the novel substances in the study were somewhat similar to one another and in many cases do not represent different kinds of substances even for adults (e.g., different colors of plastic or types of wood). This might have led children to construe novel labels as referring to things other than kind of solid substance in order to avoid having two names for what they conceptualize as the same kind of substance.

The results of the word-learning task in this experiment show that children as young as 2V2 years old can learn names for solid substances if familiar objects and the actual substance names are used. Previous results suggesting that 3-year- olds are unable to learn names for solid substances must be attributed to methodological factors rather than an inability to learn names for solid substances.

The results of the elicitation task suggest that 2V2- to 3V_,-year-olds do not know many names for solid substances and that 3- to 3V2-year-olds know more names for solid substances than 2V2- to 3-year-olds. These results are consistent with previous findings suggesting that children younger than 3V,_ years of age know very few, if any, names for solid substances (Dickinson, 1986; Soja, 1991). Although children do not know many names for solid substances, they do know that substance names occur with the locution made of. This is reflected in the many incorrect substance names given in response to the question, What is this made of?.

Although children generally responded to the question What is this made oj~?. with substance names, this does not, in itself, provide evidence regarding whether the words are being mapped onto kind of solid substance or not. It is possible that children knew that made of is followed by a list of some words but did not know what those words refer to. However, the explanations of property differences between objects made of different substances provided three types of evidence that when children learn names for solid substances, they map the words onto kind of solid substance. First, the question that elicited the explanations did not require children to respond with names of substances and thus children's use of names for solid substances in their explanations shows that they know that the property being probed is related to the object's substance kind rather than some other property. The use of substance names in these explanations provides evidence that the substance names are actually being mapped onto substance. Second, children often provided explanations that mentioned the wrong substance. Children could not have any association between a given property and the wrong substance (e.g., between transparency and wood) and so

96 Sandeep Prasada

the explanations that mentioned the wrong substance suggest that children know that the substance is relevant but do not know the correct substance name. Third, the explanations containing the locution made of without a substance name suggest that children understand the meaning of made of and realize that what the object is made of is relevant to the property difference but do not know a name for the substance that the object is made of.

In addition to providing evidence that children map the names for solid substances onto substance, the explanations provided evidence that children represent the names as mass nouns. If children represented the words as adjectives one would not expect them to use the words with the locution made of and one would expect at least a few prenominal uses of the substance words. Children used the words with the locution made of without a plural, used the substance names without a determiner, and never used the words prenominally. These data strongly suggest that children represent names for solid substances as mass nouns and thus quantify them in terms of portions. It is possible that in addition to representing names for solid substances as mass nouns, children represent these words as adjectives but use them only predicatively.

Finally, the results of the explanation task suggest that children between the ages of 2'/,. and 3'/2 years of age know some properties of solid substances as demonstrated by the many responses that mentioned solid substances. Their knowledge of properties of solid substances is limited, however. This limited knowledge is reflected in the large number of failures to respond to the explanation question. The older children gave more explanations than the younger children suggesting that this is an age at which children are learning about the properties of solid substances. This difference in knowledge of properties of solid substances contrast with children's ability to learn names for solid substances; the younger children were as successful as the older children in learning names for solid substances. It is possible, however, that the explanation task underestimates children's nonlinguistic knowledge of solid substances as it is linguistically very demanding. A simpler, nonlinguistic inference task was used in Experiment 2 to assess children's knowledge of properties of solid substances. The task was identical in structure to the word-learning task except that instead of teaching a word, a property related to the object's substance was pointed out and then children were given a response set and asked to give the object having the same property rather than the same name.

EXPERIMENT 2

This experiment used materials used in the word-learning task in Experiment 1 to investigate 21/2- to 3V2-year-olds' inferences about properties of solid substances that are independent of the manner in which one quantifies solid substances. Children were shown a substance-related property of an object (e.g., can squeeze a sponge ball) and were then asked to predict which object in the response set would have the same property.


Subjects Thirty-two children from day-care centers in the Cambridge-Boston area participated. They were divided into a younger group ranging in age from 2;4 to 2;9 (M age = 2;7) and an older group ranging in age from 2;10 to 3;7 (M age = 3;3).

Materials One of the objects from each pair of objects used in the teaching set of the word- learning task was used as the object for which a substance-related property was demonstrated. Only one object of each pair was used so that only "positive" (e.g., why can squeeze (sponge) ball rather than why cannot squeeze (wooden) ball) properties could be probed. The properties that were probed were those that were used in the elicitation task. The response set was identical to the one used in the word-learning task in Experiment 1 except for the following changes: (a) The plastic ball was replaced with a tennis ball because the plastic ball was squeeza- ble, and (b) the cork tile was replaced by a slate tile because the cork tile was too light. The complete set of stimuli used in this experiment is shown in Table 2.

Procedure A Cookie Monster puppet showed the child one of the objects from the stimulus set (e.g., a sponge ball) and asked the child to name it. If the child did not know the name of thc object, Cookie Monster told the child the name. Cookie Monster then demonstrated a substance-related property of the object (e.g., look, you can squeeze this ball). Thc child was then allowed to perform the action needed to demonstrate the property of interest. The child was then told, " i 'm going to put this away and then bring out some things and ask you to give Cookie Monster the thing you can (squeeze) just like this." The property was demonstrated once again and then the object was put away and the response set was brought out. As in the word-learning task in Experiment 1, the response set consisted of: (a) another object of the same kind (e.g., a tennis ball), (b) a different kind of object made of the same substance (e.g., a sponge doll), and (c) a different kind of object made of a third substance but of the same kind as (b) (e.g., a wooden doll). The child was then asked to "give Cookie Monster the thing you can (squeeze)."

Results A 2 x 2 ANOVA with age and gender as the independent variables and proportion of correct responses as the dependent variable was performed. Gender was included as an independent variable because Soja (1991) found that 2V2-year-old girls made more inductions about the smell of an object on the basis of solid substance than did boys. There was a significant effect of age with the older children picking the correct answer more often than the younger children, F(1, 28) = 7.257, p < .01. All the rest of the effects were not significant. The age difference is also reflected in the number of younger and older children that got at least 4 out of 6 trials correct. Only 5 out of the 16 younger children did so,

98 Sandeep Prasada

100

u~ c o

o

80

60 ¸

4 0 '

20"

D Older

• Younger

S u b s t a n c e Object-bias error Other error

Type of Response

Figure 3. Percentage of responses that matched the demonstration objects' substance kind, object kind, or neither.

whereas 14 of the 16 older children got at least 4 out of 6 trials correct. The percentages of correct responses, object-bias errors, and other errors as a function of age are shown in Figure 3. The younger children picked the correct item on 50% of the trials, made an object-bias error on 35% of the trials, and made other errors on 15% of the trials. The proportion of correct responses made by the younger children differed from chance responding when chance performance was taken to be 33%, t(15) = 2.828, p < .01, but not when chance performance was taken to be 50%. The older children, on the other hand, picked the correct item on 73% of the trials, made an object-bias error on 23% of the trials, and made other errors on 4% of the trials. The proportion of correct responses given by the older children was significantly greater than that expected by chance (33%), t(15) = 6.746, p < .001. This was the case even when the conservative estimate of chance was employed (50%), t(15) = 3.905, p < .001. 3

The distribution of responses as a function of substance is given in Table 4. As can be seen, the older children were successful at inferring that the property is

3For the glass trials, children were asked "which thing will you be able to see Cookie Monster through" while Cookie Monster was not visible. This required children to make an inference but given that the inference may have been different or easier than the other inferences, the data was also analyzed without the glass trials. The pattern of results were the same except that the younger children were not better than chance even at the 33% chance level.

Names for Solid Substances

Table 4. Percen tage of Cor rec t Responses by Substance and Age

99

Substance Younger Older

styrofoam 37.5 75.0* glass 62.5* 87.5* paper 37.5 .81.3* playdoh 68.8* 87.5* rubber 50 31.3 sponge 43.8 75.0*

*Significantly greater than chance (33%), p < .05.

related to the substance of which the object is made for all substances except rubber. The results of the rubber trial are probably misleading, however, because the object response was a cardboard tube which could be bent, especially by the older children. The younger children, on the other hand, were largely unsuc- cessful at predicting that the object made of the same substance would have the same property. The younger children only performed well on the trials that tested properties of playdoh and glass.

Discussion The results of this experiment show that there is a great deal of development between the ages of 272 and 3 years of age in children's knowledge of the connection between certain properties of objects and the solid substance of which the object is made. This result is consistent with the results of the explanation task in Experiment 1 in which it was found that the children in the older group gave more explanations that were relevant to the substance-related property difference than did children in the younger group. Of the properties probed in Experiment 2, the 2J/2-year-olds knew only that scratchability is a property of playdoh and that transparency is a property of glass. The older children, on the other hand, knew that the properties probed were related to substance kind.

Although the younger children did not consistently attribute the properties probed to the object's substance kind, it is not the case that the younger children had a mistaken belief that the property in question is related to kind of object. This can be seen in the fact that although the younger children did not pick the substance response consistently, they picked it more often than the object response and did not pick the object response consistently. It is interesting that children do not use a default strategy of predicting that an unfamiliar property is likely to be possessed by objects of the same kind. Older children and adults have been shown to project unfamiliar properties to members of the same kind (Gelman, 1988; Osherson, Smith, Wilkie, Lopez, & Shafir, 1990). The results of the experiment presented here suggest that either 272-year-olds have not developed such a strategy, or that the children have partial knowledge of these proper-

100 Sandeep Prasada

ties, do not treat them as wholly unfamiliar, and consequently do not use a default strategy to reason about them. To distinguish between these possibilities one would have to conduct a similar experiment in which the properties probed are related to substance but are unlikely to be familiar to children of this age. If children respond the way they did in this experiment it would suggest that they have not developed the default strategy used by older children and adults. If, on the other hand, children use the default strategy, it would suggest that children in this experiment have some knowledge that the properties being probed are related to the substance of which the objects are made but that this knowledge is fragmentary.

This study adds to the studies of children's nonlinguistic inferences about solid substances by Soja (1991) and Schmidt (1987) by probing a greater number of properties and substances. The results of this experiment, along with previous studies, suggest that children's knowledge of properties of solid substances de- velops between the ages of 2t/2 and 4 years and that children learn about the connection between different substances and properties at different ages. Thus, 21/2-year-old girls base their inferences about the smell of an object on substance kind (Soja, 1991) and 3-year-olds base their inferences about flexibility, deformability, transparency, and weight on substance kind. Knowledge of other properties of solid substances, for example which substances burn or rust, does not develop until much later (Dickinson, 1982). An interesting question for future research concerns how children represent the connection between the particular substances and properties. If children's representations are of the form sponge is a substance that is deformable, then one would expect children to generalize the connection between the deformability of an object and the substance of which an object is made to other objects that are deformable. The same would not be true if the representation is of a more specific nature such as sponge objects are deformable because this would leave open the possibility that some property of sponge other than its substance (e.g., texture) is relevant to an object's deformability.

GENERAL DISCUSSION

This study presents evidence that 2V2- to 3~/2-year-olds do not know many names for solid substances but that children as young as 2t/2 years of age can learn names for solid substances. In addition, there is evidence that children represent names for solid substances as mass nouns and possibly adjectives. The study also found that there is a great deal of development in children's nonlinguistic knowledge of solid substances between the ages of 2t/2 and 3V2 years.

Young Children's Knowledge of Names for Solid Substances Although children can learn name for solid substances, children between the ages of 2Y2 and 31/2 years were found not to know many names for solid substances.


This finding confirms and extends previous findings that children younger than 3V2 or 4 years of age do not know many, if any, names for solid substances (Dickinson, 1986; Soja, 1987, 1991). The study presented here extends the previous results by testing a greater range of solid substances and by providing evidence that although children do not always know the correct extensions of the words, they do know that the words refer to kind of substance. This is similar to the findings that children often know that certain words refer to color or number without knowing which color (Carey & Bartlett, 1978) or number (Wynn, 1990). This study also presented evidence that the names for solid substances are represented as mass nouns and possibly also as adjectives.

Given the finding that even 2Vz-year-olds can learn names for solid substances, the question arises as to why children know so few names for solid substances. The simplest answer to this question would be that children do not hear these words very often. This is in fact what Soja (1991) found; caretakers do not use names for solid substances very often and there is a correlation between the frequency with which children hear names for solid substances and children's production of these names. In the current study, the lack of a correlation between the number of solid substance names produced and children's ability to learn names for solid substances also suggests that the lack of solid substance names in young children's vocabularies is probably due to the lack of opportunities to learn these words rather than an inability to learn them.

How Might Children Learn Names for Solid Substances? Children younger than 3 years of age were found to base very few nonlinguistic inferences on the basis of solid substances, yet they are able to learn names for solid substances. This raises the question of how children are able to learn names for entities they know very little about. Data from the two experiments presented here suggest the following mechanism: Children learn that the locution made of requires a substance name to follow it in the context of a nonsolid substance such as playdoh, or possibly a solid substance that they know a little about (e.g., glass). Children can then use this knowledge to identify instances of solid substances being named even though they may not know any properties of the substance being named. Substances such as playdoh and paper are likely to be helpful in the learning of the meaning of the locution made of because children often use these substances to construct objects. This could help children learn the relationship between substances and objects. Children learn the meaning of the locution made of through semantic cues and then use distributional evidence to infer the meaning of the word that follows it. If this is the case, then one would expect to find that children are able to learn names for substances that they know very little about. Children's ability to make nonlinguistic inferences about solid substances is necessarily dependent on their experience with the substance, but the ability to know that a new word names a kind of substance does not require experience with the particular substance being spoken about.

102 Sandeep Prasada

Quantification and Word Learning Given that children younger than 3 years of age base very few nonlinguistic inferences on the basis of solid substances, and the fact that 2V2-year-olds are already in the process of learning count-mass syntax (Gordon, 1985; Soja et al., 1991), it seems that solid substances do not play a role in the acquisition of count-mass syntax. The data from this study suggests that children probably use their nonlinguistic knowledge of nonsolid substances to learn the quantificational properties of mass nouns and the determiners and phrases that occur with mass nouns.

The evidence that children represent names for solid substances as mass nouns is especially interesting because it suggests that children are quantifying solid substances in terms of portions. This is in spite of the fact that children encounter solid substances in the form of objects which are quantified in terms of individuals, not portions. The results of this study suggest that children as young as 2'/2 years of age are capable of quantifying the same entity as either an individual or a substance.

Soja et al. (1991) and Dickinson's (1988) finding that children take a word used to name an to unfamiliar solid entity as referring to the entity's object kind, and a word used to name a nonsolid entity as referring to the entity's substance kind, shows that the ontological category which an unfamiliar entity belongs to constrains the manner in which the entity is quantified. Though this study provides evidence that 2V2-year-old children are capable of quantifying the same entity in terms of individuals and portions, Soja et al. (1991) and Dickinson's (1988) results suggest that children must quantify unfamiliar solid entities in terms of individuals, not portions. Similarly, an unfamiliar nonsolid entity must be quantified in terms of portions, not individuals. This conclusion is supported by Soja's (1992) finding that syntax that conflicts with the quantificational properties of objects and substances affects the extent to which 2- and 2V2-year-old children behave in accordance with Procedures 1 and 2 but does not lead children to quantify solid entities in terms of portions or nonsolid entities in terms of individuals. The extent to which the conflicting syntax affected children's projec- tions of word meaning was related to the children's mastery of the count-mass noun distinction in their productive vocabulary. Children's ability to learn names for solid substances in this study implies that Soja et al.'s (1991) Procedure I is limited to applying unfamiliar solid entities.

The limitation of the procedure to apply only to unfamiliar entities makes it possible for children to learn names for solid substances and obviates the need for a mechanism to weaken or replace the procedure at some point in development. This is a desirable state of affairs because if the procedure had to be weakened or removed at some point in development to allow the child to learn names for solid substances, one would have to posit another mechanism to account for adults accordance with Procedure 1 when learning names for unfamiliar solid entities (Markman & Wachtel, 1988). Although this study does not provide evidence


regarding whether a s imilar l imitation applies to Procedure 2 (for nonsolid en-

tities), it is l ikely that it does. The l imit ing o f the applicabil i ty o f Procedure 2 to

only unfamil iar nonsol id entities would al low the child to learn words such as

puddle which refer to a nonsolid entity but are quantif ied in terms of individuals.

Future research will establish whether 2V2-year-olds can quantify nonsolid en-

tities that are usually quantif ied in terms of portions in terms of individuals (e .g . ,

a puddle) i f they already know a name for the substance.

REFERENCES

Au, T.K., & Markman, E.M. (1987). Acquiring word meanings via linguistic contrast. Cognitive Development, 2, 217-236.

Bloom, L. (1970). Language development: Form and function bz emerging grammars. Cambridge, MA: MIT Press.

Bloom, P. (1990). Semantic structure and language development. Unpublished doctoral dissertation, Massachusetts Institute of Technology, Cambridge, MA.

Bloom, P. (in press). Possible names: The role of syntax-semantics mappings in the acquisition of nominals. Lingua.

Bowemlan, M. (1973). Early syntactic development: A cross-lhlguistic study, with special reference to Finnish. Cambridge: Cambridge University Press.

Brown, R. (1973). A first language: The early stages. Cambridge, MA: Harvard University Press. Carey, S., & Bartlett, E. (1978). Acquiring a single new word. Papers and Reports on Child

Language Development, 15, 17-29, Department of Linguistics, Stanford University. Clark, E.V. (1987). The principle of contrast: A constraint on language acquisition. In B. MacWhin-

ney (Ed.), Mechanisms of language acquisition: The 20th annual Carnegie Symposium on Cognition (pp. 1-34). Hillsdale, N J: Erlbaum.

Dickinson, D.K. (1982). The development of children's understanding of materials. Unpublished doctoral dissertation, Harvard University, Cambridge, MA.

Dickinson, D.K. ( 1986, May), Learning about materials: A study of conceptual development. Paper presented at the meeting of the Jean Piaget Society, Philadelphia, PA.

Dickinson, D.K. (1988). Learning names for materials: Factors constraining and limiting hypotheses about word meaning. Cognitive Development, 3, 15-35.

Gelman, S.A. (1988). The development of induction within natural kind and artifact categories. Cognitive Psychology, 20, 65-95.

Gelman, S.A., & Taylor, M. (1984). How two-year-old children interpret proper and common names for unfamiliar objects. Child Development, 55, 1535-1540.

Gordon, P. (1985). Evaluating the semantic categories hypothesis: The case of the count/mass distinction. Cognition, 20, 209-242.

Hall, D.G. (1990). Acquiring proper names for familiar and unfamiliar animate objects: Evidence from two-year-olds. Papers and Reports on Child Language Development, 29, 70-77.

Macnamara, J. (1982). Names for things. Cambridge, MA: Bradford/MIT Press. Macnamara, J. (1986). A border dispute. Cambridge, MA: Bradford/MIT Press. Markman, E.M. & Wachtel, G. (1988). Children's use of mutual exclusivity to constrain the mean-

ings of words. Cognitive Psychology, 20, 12 I - 157. McPherson, L.M.P. (1991). A little goes a long way: Evidence for a perceptual basis for the noun

categories COUNT and MASS. Journal of Child Language, 18, 315-338. Nelson, K. (1976). Some attributes of adjectives used by young children. Cognition, 4, 1-31. Osherson, D.N., Smith, E.E., Wilkie, O., Lopez, E., & Shafir, E. (1990). Category based induc-

tion. Psychological Review, 97, 185-200.

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Quine, v.w.o. (1960). Word and object. Cambridge, MA: MIT Press. Schmidt, H.J. (1987). Inferences about smell: A matter of substance. Unpublished raw data. Soja, N.N. (1987). Ontological constraints on 2-year-olds' induction of word meanings. Un-

published doctoral dissertation, Massachusetts Institute of Technology, Cambridge, MA. Soja, N.N. (1991). Young children's difficult., with solid substance words. Unpublished manuscript.

Northeastern University, Boston, MA. Soja, N.N. (1992). Inferences about the meanings of nouns: The relationship between perception and

syntax. Cognitive Development, 7, 29-45. Soja, N.N., Carey, S., & Spelke, E.S. (1991). Ontological categories guide young children's induc-

tions of word meaning: Object terms and substance terms. Cognition. 38, 179-211. Taylor, M., & Gelman, S.A. (1988). Adjectives and nouns: Children's strategies for learning new

words. Child Development, 59. 411-419. Wynn, K. (1990). Children's understanding of counting. Cognition, 36. 155-193.

learning names for solid substances: quantifying solid entities in terms of portions

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