Journalof Speech and Hearing Research, Volume 34, 1121-1129, October 1991
The Continuity of Babble and Speech in Children With Specific Expressive Language Delay Grover J. Whitehurst Meagan Smith Janet E. Fischel David S. Arnold Christopher J. Lonigan State University of New York at Stony Brook
RaWaaRmameamWaaaaaam
A natural language sample of babble and words was obtained for 37 two-year-olds with severe specific expressive language delay. Variables derived from this sample were used to predict individual differences inexpressive language scores 5 months later. The rate of word use was positively related to language outcome, whereas rate of vowel babble was negatively related to outcome. Together, these two variables accounted for 41% of the variance inlanguage outcome test scores. The addition of one nonlinguistic variable, a measure of behavior problems, allowed the prediction equation to account for over 50% of the variance inexpressive language outcome. The single strongest correlate of language outcome was the proportion of consonantal to vowel babble. The degree of social responsiveness of babble and the length of babble were not related to later language scores. These findings indicate that for children with specific expressive language delay, vowel babble competes with expressive language, consonantal babble facilitates expressive language, and the length and social responsiveness of babble are independent of expressive language. The continuity between babble and speech is multidimensional and multidirectional. KEY WORDS: specific expressive language delay, babbling, language development, phonology
Theorists have debated for decades whether infant babble is continuous with the development of early speech (e.g., Jacobson, 1941/1968; Jesperson, 1925; Mowrer, 1952). Most recently, the pendulum of opinion has swung toward a continuity position on the basis of a strong body of research showing that babble and speech share phonological characteristics within target languages, and further, within individual children. For example, Oiler, Wieman, Doyle, and Ross (1975) found that infants' "favorite" sounds during babble were inserted where they did not belong in early words, and "non-favored" sounds were omitted when they should have been uttered. Similarly, Vihman, Macken, Miller, Simmons, and Miller (1985) found that the consonant distribution, vocalization length, and phonotactic structure of babbled sounds for 9 infants were virtually identical to those of their first words. DeBoysson-Bardies and colleagues (deBoysson-Bardies, Halle, Sagart, & Durand, 1989; deBoysson-Bardies, Sagart, & Durand, 1984) have demonstrated, both phonetically and acoustically, that infant babbling patterns are significantly different across target languages, suggesting that prelinguistic babbling is somehow preparatory to first words. This research, when considered inthe context of related work, makes a strong case for the phonological continuity of babble with speech. But what of the other facets of these phenomena? Babble and speech are multidimensional. They include acoustic, articulatory, social, and cognitive elements. It is possible that babble is continuous with early speech on some, but not all, of these dimensions. In general, the question of the continuity between babble and the development of language has been © 1991, American Speech-Language-Hearing Association
1121
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Journal of Speech and Heanng Research
considered in terms that are far too broad. This may explain the oscillating fortunes of the continuity and discontinuity positions through the past few decades, as well as the persistent inability to accurately and consistently predict later lexical development from babbling patterns (Menyuk, Liebergott, and Schultz, 1986; Vihman, 1986). Different aspects of babble might be related to language development in different ways, depending on a variety of contextual factors, including the age and characteristics of the child. The present study is an attempt to address issues of the continuity between babble and language development within a differentiated framework. Our concern is with a particular type of child, 2-year-olds with specific expressive language delay (ELD). Within that population, we wanted to determine whether the frequency, complexity, and/or social function of babble facilitate the later acquisition of expressive vocabulary. A facilitative relation on all of these dimensions would mean that among a population of ELD children at the very beginnings of acquisition of expressive vocabulary, those who babbled most frequently, with the greatest complexity, and with a greater social use of babble to interact with mother would acquire vocabulary faster than those children who were at lower levels on these dimensions. There is very little relevant research or theory on the relations between babble and speech in ELD children. StoelGammon (1991) has pointed out that children with limited phonetic repertoires necessarily have limited early lexicons, or, alternatively, make atypical substitution errors to compensate for their phonological deficits. However, the opposite does not necessarily follow; that is, children with limited early lexicons need not have restricted phonetic repertoires. Pertinent to this point, Stoel-Gammon (1989) reported on the babble of 2 late talkers. One of these children displayed a low frequency of variegated babbles; the other child's babbling was equivalent to that of his normally developing peers. Research with normally developing children suggests that sophisticated function, as well as frequency and form, of babble should facilitate expressive language. Vihman and Miller (1988), for instance, found continuity of function between babble and words for children in the earliest stages of the acquisition of expressive vocabulary. They analyzed 30-min samples of the vocalizations of 7 children at two criterion points: the first sample (of weekly recordings) in which 4 word types were identifiable and the first 15-word criterion session. The mean number of word types more than doubled (from 9 to 19) across sessions, but the proportion of words in relation to nonword vocalizations rose relatively slightly, from 24 to 32%. The authors interpreted this finding as indicative of the continuity of function between babble and first words; even by the 15-word criterion session (which corresponded to an expressive vocabulary of approximately 30 words), children continued to rely heavily upon babble to communicate. At this point 57% of their utterances were interactive nonwords. Halliday (1975) and Bates, Benigni, Bretherton, Camaioni, and Volterra (1979) have posited a mechanism for such continuity: the child's understanding of symbolic and pragmatic functions. Presumably children who demonstrate that their vocalizations can be used to make comments to and
Downloaded From: http://jslhr.pubs.asha.org/ by a La Trobe Univ User on 02/12/2016 Terms of Use: http://pubs.asha.org/ss/rights_and_permissions.aspx
34
1121-1129
October 1991
requests of adults have acquired a conceptual prerequisite for expressive vocabulary. On the other hand, one might conceptualize babble and expressive vocabulary as becoming competitive communication systems, especially in the functional realm, by the time children are 2 years old. ELD children who produce frequent, complex, or more pragmatically functional babbles might have less motivation to acquire words than children who have a less developed babble repertoire. Clarification of this issue would have important clinical implications for children whose expressive language is delayed. For example, if frequent communicative babble is positively correlated with later acquisition of words, then one might attempt to intervene so as to increase such babble in 2-year-olds who have not developed expressive vocabulary and who also babble at low rates. Knowing the relations between babble and early words in ELD children would also allow improved predictions of the course of language development for individual children. This could be very useful to practitioners and parents in deciding how to manage the condition. In the present research, we examined the vocalizations of ELD children while they were interacting with their mothers. Form complexity, frequency, and social function of babble were measured and related to expressive language ability assessed 5 months later. We expected that a facilitative relation between babble and later expressive development in ELD children would be reflected in positive correlations between the frequency, consonantal complexity, and social function of prespeech vocalizations on the one hand, and later vocabulary size on the other. In other words, children who were more sophisticated babblers should subsequently acquire more expressive speech than less sophisticated babblers. In contrast, competition between babble and the development of expressive language would be reflected in negative correlations between babble sophistication and the subsequent emergence of expressive language. Noncontinuity, or independence, would be indicated by the absence of a relation between the measured dimensions of babble and later language. Further, a differentiated relation between babble and language would be indicated by variation in outcome (continuity, competition, or independence) across the measured dimensions of babble (form, frequency, and function). Method Subjects Developmental expressive language disorder is defined as a "marked impairment in the development of expressive language that is not explainable by mental retardation or inadequate schooling and that is not due to a pervasive developmental disorder, hearing impairment, or a neurologic disorder" (American Psychiatric Association, 1987). That definition applies to the subjects of this research. However, we prefer the term specific expressive language delay (ELD): The adjective specific is useful in distinguishing children with ELD from children who also experience receptive delay.
Whitehurst et al.: Babble and Expressive Delay
Further, the noun delay carries less excess meaning than the noun disorder. Thirty-seven 2-year-olds with ELD participated in the study. Mean age at initial assessment was 28 months. Mean age at 5-month follow-up was 33 months. There were 34 males and 3 females in the sample. All subjects were from middle-class families living on Long Island, New York, and were recruited through local newspaper announcements and physician referrals. Subjects were participants in an ongoing longitudinal study of expressive language delay (Whitehurst, Fischel, Arnold, & Lonigan, in press). The present study included all ELD subjects from that larger sample for whom the relevant observational and outcome measures existed. ELD was operationalized as an expressive language score of 2.33 or more standard deviations below the mean, measured by the Expressive One-Word Picture Vocabulary Test (EOWPVT) (Gardner, 1981), and by receptive language and nonverbal intelligence of no more than one standard deviation below the mean, measured by the Peabody Picture Vocabulary Test-Revised (PPVT-R) (Dunn & Dunn, 1981) and the Leiter International Performance Scales (Leiter, 1976), respectively. The EOWPVT criterion was chosen because it represents severe delay in a statistical sense and because children scoring at the criterion were unlikely to have more than a few words in their expressive vocabulary. It is typically the lack of more than a few words in a child's expressive lexicon by 2 years of age that leads to parental concern about the child's language progress. The modal number of correct responses on the EOWPVT by the children in this sample was zero. The inability of most of this sample to label even pictures of such familiar items as a ball or a dog attests to the severe nature of their delay. In all cases, each child's parents, who were present during the testing session, affirmed that their child's performance on the EOWPVT was an appropriate indicator of the child's ability rather than an indication of reticence or noncompliance. The validity of the EOWPVT diagnosis was corroborated by maternal report of children's expressive vocabulary. Mothers of the delayed group reported that their children produced an average of 18 words at the time of initial diagnosis, and 14 of the children were reported to produce no more than 10 words. Maternal reports of vocabulary development have been shown to have high validity (Bates, Bretherton, & Snyder, 1988; Beeghly, Jernberg, & Burrows, 1989). To place these maternal reports in context, Dale and Thal (1989) indicate that the average toddler at 24 months has a productive vocabulary of over 300 words. Analyses of naturalistic language samples further confirmed the severe expressive deficits of the ELD children. Audiotapes were collected of 10 of the ELD children's families interacting at dinnertime in the home, using the procedure described in Whitehurst et al., 1988. The median number of unique words produced by ELD children per dinnertime session was 1.5. A control group of normally developing children of the same age as the ELD group, recorded under identical conditions, produced a median of 32 unique words per session (Whitehurst, Arnold et al., in press). To further place this observation in context, StoelGammon (1989) operationally defined the meaningful
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1123
speech stage as the child's production of 10 or more different adult-based words in 2 hr of interaction with parents. All of her sample of 34 children, who were selected on the basis of normal development at 9 months of age, had reached this criterion by 24 months of age, even 2 children she defined as late talkers. According to our analysis of mealtime interactions, no ELD child in the present sample had reached the stage of meaningful speech, even though they were all more than 24 months of age. Parents were strongly advised to obtain an audiological assessment for all children who were diagnosed as having ELD. We have reported audiometric data on a superset of this sample elsewhere (Fischel, Whitehurst, Lonigan, & Jordan, 1991). The majority of the sample had Type A tympanograms, and no child had a threshold for speech of more than 25 dB HL. The profile of the ELD sample is similar to what might be expected from a random sample of preschoolers (Roeser, Soh, Duckel, & Adams, 1978). We have also reported elsewhere the medical history of ear disease from birth to 30 months for a superset o this sample and a normally developing control group (Lonigan, Fischel, Whitehurst, Arnold, & Valdez-Menchaca, in press). The number of episodes of ear problems was virtually identical In the two groups, averaging about 2 per child over the first 2 years of life. Physical disabilities, autism, or other pervasive developmental disorders were ruled out through observation of the child and detailed parent interview. In summary, the subjects of this research had very limited productive lexicons for their age as measured on a standardized test, by maternal report, and by natural speech samples; at the same time their receptive lexicons and nonverbal abilities were at age-appropriate levels. Hearing status was normal, as was the history of ear disease. Subject characteristics are reported in detail in Table 1. Procedure Children were seen on two occasions. Both sessions occurred in a room with the mother and one experimenter present. Mothers were instructed to keep themselves occuTABLE 1. Subject characteristics at diagnosis. Variable
M
SD
Chronological age inmonths 27.62 3.16 Receptive age standard score (PPVT) a 103.76 13.86 Expressive age standard score (EOWPVT)b 53.60 4.78 Nonverbal ratio IQ (Leiter) 114.71 22.64 Expressive vocabulary (maternal report) 18.35 13.98 No. physician visits for otitis 0-24 months 2.03 1.99 (med. record) Note. PPVT = Peabody Picture Vocabulary Test-Revised; EOWPVT = Expressive One-Word Picture Vocabulary Test. alQ scores are not available on the PPVT for children under 30 months of age. A ratio IQwas calculated for these children using the formula 100 x mental age/chronological age. bThe lowest precise standard score given by the EOWPVT manual is 55. Children
performing at lower levels are given the imprecise tabled value of "
The Continuity of Babble and Speech in Children With Specific Expressive Language Delay Grover J. Whitehurst Meagan Smith Janet E. Fischel David S. Arnold Christopher J. Lonigan State University of New York at Stony Brook
RaWaaRmameamWaaaaaam
A natural language sample of babble and words was obtained for 37 two-year-olds with severe specific expressive language delay. Variables derived from this sample were used to predict individual differences inexpressive language scores 5 months later. The rate of word use was positively related to language outcome, whereas rate of vowel babble was negatively related to outcome. Together, these two variables accounted for 41% of the variance inlanguage outcome test scores. The addition of one nonlinguistic variable, a measure of behavior problems, allowed the prediction equation to account for over 50% of the variance inexpressive language outcome. The single strongest correlate of language outcome was the proportion of consonantal to vowel babble. The degree of social responsiveness of babble and the length of babble were not related to later language scores. These findings indicate that for children with specific expressive language delay, vowel babble competes with expressive language, consonantal babble facilitates expressive language, and the length and social responsiveness of babble are independent of expressive language. The continuity between babble and speech is multidimensional and multidirectional. KEY WORDS: specific expressive language delay, babbling, language development, phonology
Theorists have debated for decades whether infant babble is continuous with the development of early speech (e.g., Jacobson, 1941/1968; Jesperson, 1925; Mowrer, 1952). Most recently, the pendulum of opinion has swung toward a continuity position on the basis of a strong body of research showing that babble and speech share phonological characteristics within target languages, and further, within individual children. For example, Oiler, Wieman, Doyle, and Ross (1975) found that infants' "favorite" sounds during babble were inserted where they did not belong in early words, and "non-favored" sounds were omitted when they should have been uttered. Similarly, Vihman, Macken, Miller, Simmons, and Miller (1985) found that the consonant distribution, vocalization length, and phonotactic structure of babbled sounds for 9 infants were virtually identical to those of their first words. DeBoysson-Bardies and colleagues (deBoysson-Bardies, Halle, Sagart, & Durand, 1989; deBoysson-Bardies, Sagart, & Durand, 1984) have demonstrated, both phonetically and acoustically, that infant babbling patterns are significantly different across target languages, suggesting that prelinguistic babbling is somehow preparatory to first words. This research, when considered inthe context of related work, makes a strong case for the phonological continuity of babble with speech. But what of the other facets of these phenomena? Babble and speech are multidimensional. They include acoustic, articulatory, social, and cognitive elements. It is possible that babble is continuous with early speech on some, but not all, of these dimensions. In general, the question of the continuity between babble and the development of language has been © 1991, American Speech-Language-Hearing Association
1121
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002 2-468 5913405111$0 1.00/0
1122
Journal of Speech and Heanng Research
considered in terms that are far too broad. This may explain the oscillating fortunes of the continuity and discontinuity positions through the past few decades, as well as the persistent inability to accurately and consistently predict later lexical development from babbling patterns (Menyuk, Liebergott, and Schultz, 1986; Vihman, 1986). Different aspects of babble might be related to language development in different ways, depending on a variety of contextual factors, including the age and characteristics of the child. The present study is an attempt to address issues of the continuity between babble and language development within a differentiated framework. Our concern is with a particular type of child, 2-year-olds with specific expressive language delay (ELD). Within that population, we wanted to determine whether the frequency, complexity, and/or social function of babble facilitate the later acquisition of expressive vocabulary. A facilitative relation on all of these dimensions would mean that among a population of ELD children at the very beginnings of acquisition of expressive vocabulary, those who babbled most frequently, with the greatest complexity, and with a greater social use of babble to interact with mother would acquire vocabulary faster than those children who were at lower levels on these dimensions. There is very little relevant research or theory on the relations between babble and speech in ELD children. StoelGammon (1991) has pointed out that children with limited phonetic repertoires necessarily have limited early lexicons, or, alternatively, make atypical substitution errors to compensate for their phonological deficits. However, the opposite does not necessarily follow; that is, children with limited early lexicons need not have restricted phonetic repertoires. Pertinent to this point, Stoel-Gammon (1989) reported on the babble of 2 late talkers. One of these children displayed a low frequency of variegated babbles; the other child's babbling was equivalent to that of his normally developing peers. Research with normally developing children suggests that sophisticated function, as well as frequency and form, of babble should facilitate expressive language. Vihman and Miller (1988), for instance, found continuity of function between babble and words for children in the earliest stages of the acquisition of expressive vocabulary. They analyzed 30-min samples of the vocalizations of 7 children at two criterion points: the first sample (of weekly recordings) in which 4 word types were identifiable and the first 15-word criterion session. The mean number of word types more than doubled (from 9 to 19) across sessions, but the proportion of words in relation to nonword vocalizations rose relatively slightly, from 24 to 32%. The authors interpreted this finding as indicative of the continuity of function between babble and first words; even by the 15-word criterion session (which corresponded to an expressive vocabulary of approximately 30 words), children continued to rely heavily upon babble to communicate. At this point 57% of their utterances were interactive nonwords. Halliday (1975) and Bates, Benigni, Bretherton, Camaioni, and Volterra (1979) have posited a mechanism for such continuity: the child's understanding of symbolic and pragmatic functions. Presumably children who demonstrate that their vocalizations can be used to make comments to and
Downloaded From: http://jslhr.pubs.asha.org/ by a La Trobe Univ User on 02/12/2016 Terms of Use: http://pubs.asha.org/ss/rights_and_permissions.aspx
34
1121-1129
October 1991
requests of adults have acquired a conceptual prerequisite for expressive vocabulary. On the other hand, one might conceptualize babble and expressive vocabulary as becoming competitive communication systems, especially in the functional realm, by the time children are 2 years old. ELD children who produce frequent, complex, or more pragmatically functional babbles might have less motivation to acquire words than children who have a less developed babble repertoire. Clarification of this issue would have important clinical implications for children whose expressive language is delayed. For example, if frequent communicative babble is positively correlated with later acquisition of words, then one might attempt to intervene so as to increase such babble in 2-year-olds who have not developed expressive vocabulary and who also babble at low rates. Knowing the relations between babble and early words in ELD children would also allow improved predictions of the course of language development for individual children. This could be very useful to practitioners and parents in deciding how to manage the condition. In the present research, we examined the vocalizations of ELD children while they were interacting with their mothers. Form complexity, frequency, and social function of babble were measured and related to expressive language ability assessed 5 months later. We expected that a facilitative relation between babble and later expressive development in ELD children would be reflected in positive correlations between the frequency, consonantal complexity, and social function of prespeech vocalizations on the one hand, and later vocabulary size on the other. In other words, children who were more sophisticated babblers should subsequently acquire more expressive speech than less sophisticated babblers. In contrast, competition between babble and the development of expressive language would be reflected in negative correlations between babble sophistication and the subsequent emergence of expressive language. Noncontinuity, or independence, would be indicated by the absence of a relation between the measured dimensions of babble and later language. Further, a differentiated relation between babble and language would be indicated by variation in outcome (continuity, competition, or independence) across the measured dimensions of babble (form, frequency, and function). Method Subjects Developmental expressive language disorder is defined as a "marked impairment in the development of expressive language that is not explainable by mental retardation or inadequate schooling and that is not due to a pervasive developmental disorder, hearing impairment, or a neurologic disorder" (American Psychiatric Association, 1987). That definition applies to the subjects of this research. However, we prefer the term specific expressive language delay (ELD): The adjective specific is useful in distinguishing children with ELD from children who also experience receptive delay.
Whitehurst et al.: Babble and Expressive Delay
Further, the noun delay carries less excess meaning than the noun disorder. Thirty-seven 2-year-olds with ELD participated in the study. Mean age at initial assessment was 28 months. Mean age at 5-month follow-up was 33 months. There were 34 males and 3 females in the sample. All subjects were from middle-class families living on Long Island, New York, and were recruited through local newspaper announcements and physician referrals. Subjects were participants in an ongoing longitudinal study of expressive language delay (Whitehurst, Fischel, Arnold, & Lonigan, in press). The present study included all ELD subjects from that larger sample for whom the relevant observational and outcome measures existed. ELD was operationalized as an expressive language score of 2.33 or more standard deviations below the mean, measured by the Expressive One-Word Picture Vocabulary Test (EOWPVT) (Gardner, 1981), and by receptive language and nonverbal intelligence of no more than one standard deviation below the mean, measured by the Peabody Picture Vocabulary Test-Revised (PPVT-R) (Dunn & Dunn, 1981) and the Leiter International Performance Scales (Leiter, 1976), respectively. The EOWPVT criterion was chosen because it represents severe delay in a statistical sense and because children scoring at the criterion were unlikely to have more than a few words in their expressive vocabulary. It is typically the lack of more than a few words in a child's expressive lexicon by 2 years of age that leads to parental concern about the child's language progress. The modal number of correct responses on the EOWPVT by the children in this sample was zero. The inability of most of this sample to label even pictures of such familiar items as a ball or a dog attests to the severe nature of their delay. In all cases, each child's parents, who were present during the testing session, affirmed that their child's performance on the EOWPVT was an appropriate indicator of the child's ability rather than an indication of reticence or noncompliance. The validity of the EOWPVT diagnosis was corroborated by maternal report of children's expressive vocabulary. Mothers of the delayed group reported that their children produced an average of 18 words at the time of initial diagnosis, and 14 of the children were reported to produce no more than 10 words. Maternal reports of vocabulary development have been shown to have high validity (Bates, Bretherton, & Snyder, 1988; Beeghly, Jernberg, & Burrows, 1989). To place these maternal reports in context, Dale and Thal (1989) indicate that the average toddler at 24 months has a productive vocabulary of over 300 words. Analyses of naturalistic language samples further confirmed the severe expressive deficits of the ELD children. Audiotapes were collected of 10 of the ELD children's families interacting at dinnertime in the home, using the procedure described in Whitehurst et al., 1988. The median number of unique words produced by ELD children per dinnertime session was 1.5. A control group of normally developing children of the same age as the ELD group, recorded under identical conditions, produced a median of 32 unique words per session (Whitehurst, Arnold et al., in press). To further place this observation in context, StoelGammon (1989) operationally defined the meaningful
Downloaded From: http://jslhr.pubs.asha.org/ by a La Trobe Univ User on 02/12/2016 Terms of Use: http://pubs.asha.org/ss/rights_and_permissions.aspx
1123
speech stage as the child's production of 10 or more different adult-based words in 2 hr of interaction with parents. All of her sample of 34 children, who were selected on the basis of normal development at 9 months of age, had reached this criterion by 24 months of age, even 2 children she defined as late talkers. According to our analysis of mealtime interactions, no ELD child in the present sample had reached the stage of meaningful speech, even though they were all more than 24 months of age. Parents were strongly advised to obtain an audiological assessment for all children who were diagnosed as having ELD. We have reported audiometric data on a superset of this sample elsewhere (Fischel, Whitehurst, Lonigan, & Jordan, 1991). The majority of the sample had Type A tympanograms, and no child had a threshold for speech of more than 25 dB HL. The profile of the ELD sample is similar to what might be expected from a random sample of preschoolers (Roeser, Soh, Duckel, & Adams, 1978). We have also reported elsewhere the medical history of ear disease from birth to 30 months for a superset o this sample and a normally developing control group (Lonigan, Fischel, Whitehurst, Arnold, & Valdez-Menchaca, in press). The number of episodes of ear problems was virtually identical In the two groups, averaging about 2 per child over the first 2 years of life. Physical disabilities, autism, or other pervasive developmental disorders were ruled out through observation of the child and detailed parent interview. In summary, the subjects of this research had very limited productive lexicons for their age as measured on a standardized test, by maternal report, and by natural speech samples; at the same time their receptive lexicons and nonverbal abilities were at age-appropriate levels. Hearing status was normal, as was the history of ear disease. Subject characteristics are reported in detail in Table 1. Procedure Children were seen on two occasions. Both sessions occurred in a room with the mother and one experimenter present. Mothers were instructed to keep themselves occuTABLE 1. Subject characteristics at diagnosis. Variable
M
SD
Chronological age inmonths 27.62 3.16 Receptive age standard score (PPVT) a 103.76 13.86 Expressive age standard score (EOWPVT)b 53.60 4.78 Nonverbal ratio IQ (Leiter) 114.71 22.64 Expressive vocabulary (maternal report) 18.35 13.98 No. physician visits for otitis 0-24 months 2.03 1.99 (med. record) Note. PPVT = Peabody Picture Vocabulary Test-Revised; EOWPVT = Expressive One-Word Picture Vocabulary Test. alQ scores are not available on the PPVT for children under 30 months of age. A ratio IQwas calculated for these children using the formula 100 x mental age/chronological age. bThe lowest precise standard score given by the EOWPVT manual is 55. Children
performing at lower levels are given the imprecise tabled value of "
