The development of social toy play and language in infancy☆3

Infant Behavior & Development 24 (2001) 1–25

Articles

The development of social toy play and language in infancy夞 Lisa A. Newland*, Lori A. Roggman, Lisa K. Boyce Department of Family and Human Development, Utah State University, Logan, UT 84322-2905, USA Received 6 January 1999; revised in revised form 25 April 2000; accepted 6 March 2001

Abstract This longitudinal study examined the development of mother-infant social toy play in relation to infant language in two samples, one from 11 to 14 months (n ⫽ 70), and another from 14 to 17 months (n ⫽ 51) infant age. Infants were videotaped during a laboratory free-play session with mothers and were also assessed for language development. Individual variations in mother and infant social toy play behaviors were stable over time, but the frequency of infant initiations and maternal responses increased over time, especially from 11 to 14 months. Maternal responses to infant toy initiations, as well as manipulation and labeling of toys at 11 months were related to infant language at 14 months, while maternal coordinations with infants at 14 months were related to infant language at 17 months. The implications of mother and infant involvement in social toy play are discussed in relation to infant language development. © 2001 Elsevier Science Inc. All rights reserved. Keywords: Language development; Mother-infant play; Social interactions; Maternal responses; Infant play initiations

夞 This research was funded by a University Faculty Grant to Lori Roggman from the Vice President for Research at Utah State University, 1990 –1992, by a College of Family Research Grant to Lori Roggman, 1998 –2000, by a Fellowship to Lisa Newland from the Vice President for Research at Utah State University, 1997–1998, and by a College of Family Life Fellowship to Lisa Newland, 1998 –2000. * Corresponding author. Division of Counseling and Psychology in Education, The University of South Dakota, 414 East Clark Street, Vermillion, South Dakota 57069. Tel.: ⫹1-605-677-6308; fax: ⫹1-605-677-5438. E-mail address: [email protected] (L.A. Newland). 0163-6383/01/$ – see front matter © 2001 Elsevier Science Inc. All rights reserved. PII: S 0 1 6 3 - 6 3 8 3 ( 0 1 ) 0 0 0 6 7 - 4

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1. Introduction Early language develops in social contexts that involve adults and infants interacting jointly with objects, such as sharing toys during play (Bakeman & Adamson, 1984; Dunham & Dunham, 1992; Laasko, Poikkeus, Eklund & Lyytinen, 1999; Rollins, Marchman & Mehta, 1998; Saxon, 1997; Smith et al., 1996; Spencer & Meadow-Orlans, 1996; TamisLeMonda & Bornstein, 1989; Tomasello, 1990; Tomasello & Farrar, 1986). The specific behaviors required for mothers and infants to share and look at objects together develop over time, but how these behaviors are related to the early development of language has not been fully explored. This study examines age changes, from 11 to 17 months, in mother-infant interactions with toys in relation to changes in infant language development. Mother-infant toy play has been linked to developing infant language in three ways. First, across the first and second year of life, mother-infant toy play becomes more complex, mutual, and extensive, while during the same time communication becomes more effective, reciprocal, and verbal (Messinger & Fogel, 1998). This coincidence of timing suggests a link between social play and emerging language. Second, mother-infant toy play provides a context for attending to the same objects, an important context for learning language. Third, within this context of shared attention, mothers use and encourage infants to use words and gestures. Each of these links from mother-infant toy play to infant language is discussed. The first and most general link that has been established is the increasing complexity of both social play and language early in the second year of life. Initially, infants are “onlookers” during social interactions with toys, passively observing and reacting to a more skilled partner’s play with objects. Later, as they enter their second year, infants begin initiating play interactions with toys, coordinating their behavior with a play partner, and exchanging toys (Dunham & Moore, 1995; Tomasello, 1995). An infant may initiate a toy interaction with the mother by pointing to a toy or offering it to her. The mother and infant may then coordinate their play by responding mutually to the toy and each other or by passing the toy back and forth between them. Infants offer toys to establish and share a social contact, and by doing so create additional opportunities for shared interactions (Messinger & Fogel, 1998). During this same age period, mothers use several strategies to involve infants in play. These strategies change with infant developmental level and are correlated with infant language. During the first year, when mothers direct or encourage attention towards objects, infants play more symbolically, explore objects more frequently, and have greater receptive and productive vocabularies (Bornstein & Tamis-LeMonda, 1990; Ruddy & Bornstein, 1982; Tamis-LeMonda & Bornstein, 1989; Vibbert & Bornstein, 1989). Then during the second year, infants begin initiating more play, and mothers more often respond verbally to infants’ initiations (Baumwell, Tamis-LeMonda & Bornstein, 1997) and become less directive (Scho¨lmerich, Lamb, Leyendecker & Fracasso, 1997). The extent to which mothers shift their behaviors from directing toy play to responding to infant toy play is associated with later infant play and language. Maintaining infant attention towards toys, introducing toys to unengaged infants, and responding to the infant’s lead in play are all associated with increases in the level of infant play as well as growth in infant expressive language and gestural abilities (Carpenter, Nagell & Tomasello, 1998; Smith et al., 1996; Tomasello & Farrar, 1986). In contrast, redirecting focused infant attention away from a toy decreases

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infant complexity of play and is related to less sophisticated language development across the second year (Bornstein & Tamis-LeMonda, 1990; Landry, Garner, Swank & Baldwin, 1996; Tomasello & Farrar, 1986). The second and more specific link between play and language is the link between coordinated play with toys and infant language acquisition. When mothers and infants share toys, they must coordinate both their attention to the toys and their actions with the toys. According to Bruner (1977, 1983), coordinated actions with objects help to establish shared meanings that directly contribute to language learning. Coordinated interactions within play routines between adults and infants allow for the cultural transmission of language through several critical features, such as simple content, repetitions, and clear adult-child role structures. Throughout these familiar routines, both mother and infant can interpret the intent of the communication by “making the expression fit” the immediate and cultural context (Bruner, 1983). Within coordinated toy play, both joint attention and joint actions on objects are building infant language skills by modifying the language environment (Bruner, 1983; Dunham & Dunham, 1992; Mundy & Gomes, 1998; Rollins et al., 1998; Saxon, 1997; Tamis-LeMonda & Bornstein, 1989; Tomasello, 1990; Tomasello & Farrar, 1986). Compared to when they are not mutually focused on an object, mothers and infants speak more frequently and for longer durations during joint attention episodes (Tomasello & Farrar, 1986). Mother’s use of language that follows the infant’s attentional focus is related to infant language (Carpenter et al., 1998; Tomasello & Farrar, 1986). Mothers who respond to infant initiations create opportunities to respond verbally to their infants’ attentional focus, which in turn facilitates infant comprehension of object labels (Barratt & Roach, 1999; Dunham & Dunham, 1995). Specifically, toddlers are more likely to learn the labels of objects when the label is provided while they are attending to it, and toddlers seek verbal help more frequently when they are attending to the task (Dunham & Dunham, 1995; Hustedt & Raver, 1998). Combined, these key features of coordinated mother-infant toy play support the acquisition of language. The third link that has been established between play and language is the relation between language-rich environments and infant language development. Both the frequency and richness of maternal vocalizations during parent-child interactions are associated with infant language learning (Hart & Risley, 1995). Mother-infant play is a uniquely rich context for infant language learning because mothers provide distinct verbal cues during play situations (Reissland, 1998). For example, the use of referential language by mothers at 13 and 20 months, including labeling, describing, or asking questions about objects or activities in the environment, is related concurrently to greater infant language ability (Tamis-LeMonda & Bornstein, 1994). The frequency and richness of the language environment, including words and gestures, is likely to have a lasting effect on later communicative competence (Laasko et al., 1999). The language environment seems to be optimal during periods of shared attention during play situations, when mothers are more likely to label, describe, and point towards objects. Implied in these three links are both general and specific effects of mother-infant play on infant language. The general play context may support language development in all domains. Alternatively, specific mother and infant play behaviors during particular points in development may facilitate specific language skills. Early on, social toy play requires directiveness

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and support from an adult, but later, infants begin to coordinate toy interactions with a play partner (Bakeman & Adamson, 1984). At the end of the first year, when infant productive language skills are just emerging (Bloom, 1993), extensive input and directing from the mother may facilitate the emergence of first words. Later in the second year, however, when infants approach a “vocabulary spurt” and begin using and combining words more frequently (Bloom, 1993), maternal responsiveness and coordinations with the infant may become more critical in order to correctly label objects on which the infant is visually focused and to facilitate infant word combination skills. Developmental changes in mother-infant play interactions are likely to affect the complexity of the play context, the richness of the language environment, and thereby the development of language abilities. This study examined play and language over time to meet three objectives. The first objective was to identify developmental trends for mothers and infants in social toy play. The second objective was to clarify relations between mother-infant toy play and emerging language. The third objective was to assess unique and combined contributions of maternal and infant social toy play behaviors, at particular age points, to infant language abilities. To explore these developmental relations between mother-infant toy interactions and emerging language from 11 to 17 months, two samples were included in this study, one group from 11 to 14 months and another from 14 to 17 months.

2. Method 2.1. Participants Participants in this study included two samples of mother-infant dyads who were assessed at two time-points. Sample I included infants who were tested at 11 and 14 months of age. Sample II included infants who were tested at 14 and 17 months. 2.1.1. Sample I Participants in this sample included 98 infant-mother dyads (52 sons and 46 daughters) who were assessed at 11 months (mean age ⫽ 10.80 months). All participants were full-term, born within 4 weeks of the expected due date, and came from middle-socioeconomic-status households, M⫽43.65 on the Hollingshead (1975) Four Factor Index. The average number of siblings was 2.88. Of 98 dyads who were originally tested at 11 months, 83 (85%) returned to the lab at 14 months (mean age ⫽ 14.42). Seventy infant-mother dyads had complete data at both time points. Longitudinal data were missing for mothers and infants who were not invited to return to the lab due to incomplete data at 11 months (n ⫽ 8) or declined to revisit the lab at 14 months (n ⫽ 7). In addition, data were missing due to infant crying or technical problems (n ⫽ 5), taped play sessions that were not a full 10 min in length (n ⫽ 5), and incomplete language data at 11 months (n ⫽ 3). Group differences between infants with longitudinal language data (n ⫽ 83) and those with incomplete longitudinal data (n ⫽ 15) were tested by t tests. There were no statistically significant differences at 11 months between those who dropped from the study and those

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who returned at 14 months on the language measure, indicating that attrition was not likely related to initial differences in infant language abilities. 2.1.2. Sample II Participants in Sample II included 70 infant-mother dyads (37 sons and 33 daughters) who were assessed at 14 months (mean age ⫽ 14.24). Of those, 51 participants (28 sons and 23 daughters) were reassessed at 17 months (mean age ⫽ 17.49). All participants were full-term, born within 4 weeks of the expected due date. All infants came from middle-socioeconomicstatus households, M⫽43.67 on the Hollingshead (1975) Four Factor Index. The average number of siblings was 3.11. Of the 70 infant-mother dyads who were originally tested at 14 months, 51 (73%) returned to the lab at 17 months. Longitudinal data were missing for mothers and infants who were not invited return to the lab due to incomplete data at 14 months (n ⫽ 1) or who declined to revisit the lab at 17 months (n ⫽ 18). Group differences between infants with longitudinal language data (n ⫽ 51) and those with incomplete longitudinal data (n ⫽ 19) were tested by t tests. There were no statistically significant differences at 14 months between those who dropped from the study and those who returned at 17 months on the language measure, indicating that attrition was not likely related to initial differences in infant language abilities. 2.2. Procedures Participants in both samples were recruited by contacting mothers who had announced the birth of a child in a public newspaper. Families were first contacted by letter and then by telephone and invited to participate in the study. Those who agreed to participate were sent a packet of forms two weeks prior to scheduled visits. These forms, which elicited family demographic information, were completed and brought to the scheduled laboratory visit. Mothers and infants were videotaped for ten minutes in a laboratory playroom. The child was allowed to play on the floor with a set of developmentally appropriate toys. Toys were chosen so that a range of developmental levels of cognitive and social toy play would be elicited. Mothers were seated in a chair nearby and told that they could continue completing a questionnaire, but to respond to or help the child if needed. The play setting was structured to be similar to past studies that have elicited behaviors such as joint attention (Bakeman & Adamson, 1984; Tomasello & Farrar, 1986), directiveness and stimulation in play (Bornstein, Haynes, O’Reilly & Painter,1996; Smith et al., 1996; Tamis-LeMonda & Bornstein, 1989, 1994), socially coordinated behaviors (Laasko et al., 1999) and infant social bids (Mosier & Rogoff, 1994). Although some brief observations in unstructured naturalistic settings may provide unreliable measures, standardizing the instructions to mothers, the types of toys available, the length of observations, and the location of the observation increases the reliability of observational measures within and across contexts (Leyendecker, Lamb & Scho¨ lmerich, 1997). Even brief 10- to 15-min observations, when structured and controlled appropriately, can yield reliable “microanalytic measures such as frequency counts” of behaviors that are good indicators of underlying patterns of mother-infant interactions (Smith

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et al., 1996). Frequency of mother-infant social toy play behaviors were coded from this 10-min play session. After the 10-min play observation, each infant was tested using the Bayley Mental Development Index (Bayley, 1969). Mothers sat at a nearby table and completed another instrument not used in this study. Only performance on language items from the Bayley was used for this study. 2.3. Measures Multiple measures were used to assess social and language development, including a standardized measure of language and an observational measure of toy sharing between mothers and infants. 2.3.1. Language development The Mental Development Index of the Bayley Scales of Infant Development (Bayley, 1969) was used to assess infant language ability. For consistency in the set of items administered to infants in the study, the Bayley items were selected to overlap four months on either side of the targeted age, because the Bayley is age specific in months. Therefore, basal and ceiling rules were not followed during administration of items. Rather, each infant was administered all items in the set selected for each age period (11, 14, or 17 months). Each item was scored as pass or fail, and some items were scored using either observation or parental report, following the instructions in the Bayley (1969) manual. For this study, selected items from the Bayley MDI that assess aspects of language skill were used to generate a Total Language Score. This method of extracting language items from the Bayley MDI has been used in previous studies (Bee et al., 1982; Karrass, Mullins & Burke, 1999; Leevers & Chelius, 1999). The items selected were very similar to the items selected for expressive and receptive language scales by Reznick, Corley, and Robinson (1997). However, there were too few items included at 11 and 14 months to warrant splitting the items into two scales. Therefore, one scale measuring total language abilities was computed at each age point. Total language scores reflect the total number of items passed in each set. The Total Language score at 11 months included 11 items that assessed preverbal, receptive, and productive skills. Specifically, these items assessed infants’ ability to jabber, vocalize syllables, use gestures, indicate referents, respond to commands and requests, imitate words, and produce words. The Total Language score at 14 months included 14 items, with some overlap between 11- and 14-month items. However, at 14 months there were fewer preverbal items, as well as additional items assessing infants’ ability to respond to commands, indicate referents, and name objects and pictures. The Total Language score at 17 months included 20 items, with some overlap between 14- and 17-month items. At 17 months, there were no preverbal items included, but there were additional items assessing infants’ ability to indicate referents, name objects and pictures, respond to prepositions, make wants known using words, and produce and combine words. Because the sets of items were not the same across the three assessment points, the raw scores are not directly comparable. Cronbach’s alphas

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for the set of items in the Total Language scales were 0.53, 0.58, and 0.83, at 11, 14, and 17 months respectively, indicating moderate to strong internal consistency. 2.3.2. Social toy play Several features of mother-infant play were coded from the laboratory free-play session, and composite measures were constructed from coded behaviors. Initiations were defined as behaviors that directed the play partner’s attention towards an object by showing or offering toys that had not been part of a previous ongoing interaction. Responses were defined as behaviors that responded to toy initiations by accepting or acknowledging toy offers or shows. Manipulations/Labels were defined as instances when either the mother or infant manipulated and/or labeled objects that were offered by the play partner. Coordinations were defined as behaviors that coordinated actions with the play partner by returning toys that were offered. Directing was defined as behaviors that directed the play interaction by offering, showing, taking, or pulling back toys from the play partner. Social toy play was coded and analyzed in two steps. During the first step, the frequency of mutually exclusive sequences of social toy play behaviors was coded from videotapes of 10-min laboratory observations, in 15-s intervals. The simple frequency of the following behaviors were coded for both mothers and infants: offers, shows, retracts, ignores an offer, accepts an offer, acknowledges an offer, manipulates/labels an accepted toy, returns the toy, exchanges the toy, takes a toy, and retakes a toy (adapted from Roggman, Langlois, & Hubbs-Tait, 1987). For instance, if a mother and child exchanged a toy, the sequence would be coded as follows: infant offers the toy, mother accepts the toy by reaching her arm out and taking the toy, mother manipulates the toy by moving the parts of the toy and labels it by describing the toy (coded only once), mother performs a complex exchange by handing the toy back to the infant after it has been accepted and manipulated/labeled, infant accepts the exchange. Thus, although each of these coded behaviors are mutually exclusive, they do build upon one another. A more detailed description of the coded behaviors and variable definitions is provided in Table 1. During the second step, frequency data were collapsed to create additional composite measures. Composite measures included both frequency and proportion measures (see Table 1). Frequency scores represent a total of how frequently mothers and infants initiated and responded to interactions with toys. A composite measure of maternal initiating behaviors with toys, labeled maternal initiations, was calculated by totaling the frequency of her offers and shows. A composite measure of responses to initiations, labeled maternal responses, was calculated by totaling the frequency of accepting or acknowledging infant toy initiations. A composite measure of maternal manipulations and object labeling after accepting a toy offered by the infant was calculated and labeled maternal manipulations/labels. To assess infant contributions to social toy play, the same composite variables were created from infant codes, and labeled infant initiations, infant responses, and infant manipulations/labels. The frequency of maternal and infant responses depends, of course, on how often their play partner initiates an interaction with a toy. Previous research has indicated that mothers vary their attention-directing strategies according to infant behavior and level of development (Bornstein & Tamis-LeMonda, 1990). Therefore, it is important to assess the number of maternal behaviors in proportion to infant behaviors. Two proportion measures were

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Table 1 Social toy play variables and coded behaviors Variables and definitions

Coded behaviors

Description of behaviors

Maternal Initiations: Total frequency of maternal offers and shows Infant Initiations: Total frequency of infant offers and shows

Shows a toy

Showing play partner a toy or demonstrating how a toy works BY holding a toy up or out towards the partner while looking at, gesturing, or verbalizing to the play partner; pointing or gesturing towards a toy the partner is not holding while looking at or verbalizing to the partner; pointing out the features of a toy; showing how a toy works; showing the partner an action with a toy while calling the partner’s attention to the toy. Offering play partner a toy BY handing a toy towards the partner (within arms reach); rearranging or setting toy down in front of the partner or on play partner’s lap; throwing or kicking a ball directly to the partner. May or may not release the toy if play partner tries to accept the toy. Is offered/showed a toy, but does not accept it.

Offers a toy

Maternal Responses: Total frequency of maternal accepting or acknowledging infant’s toy initiations Infant Responses: Total frequency of infant accepting or acknowledging maternal toy initiations

Ignores an offer

Accepts an offer

Acknowledges an offer

Maternal Manipulations/Labels: Total frequency of maternal manipulations and/or object labels following infant toy initiations Infant Manipulations/Labels: Total frequency of infant’s manipulations and/or object labels following maternal toy initiations

Manipulate/Label accepted toy

Is offered/showed a toy and takes it BY reaching arms out to accept toy; allowing partner to place toy on lap (looks at partner and smiles, makes eye contact, or verbalizes recognition of toy offer while toy is being placed on lap). May say “Thank you” or “That’s nice.” Smiling, talking, or vocalizing about a toy that is shown/offered, but not accepting the toy (does not reach out for toy or allow toy to be placed on lap). Manipulating Or labeling a toy that has been accepted from the play partner BY maneuvering parts of the toy; using the toy to perform an action such as rolling a ball or turning pages of a book; imitating or completing an action begun by the play partner; engaging in functional or symbolic actions with toy; talking about an accepted toy (labeling, describing, labeling actions appropriate to the object, etc.). This was coded only once for each toy initiation.

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Table 1 (continued) Variables and definitions

Coded behaviors

Description of behaviors

Maternal Coordinations: Percent of toy initiations that mother coordinated with the infant by accepting and then attempting to return the toy, calculated as the total frequency of maternal toy returns and complex exchanges divided by the total frequency of infant initiations Infant Coordinations: Percent of maternal toy initiations that infant coordinated with the mother by accepting and then attempting to return the toy, calculated as the total frequency of infant toy returns and complex exchanges divided by the total frequency of maternal initiations Maternal-Directing: Percent of directives (shows, offers, takes, retakes, retracts) that mother initiated, calculated by dividing the total frequency of maternal directing behaviors (offer, show, take, retake, retract) by the total frequency of directing behaviors for the dyad

Returns the toy

Offering to return the toy after accepting it from the play partner BY extending toy to the play partner, but without manipulating/ labeling the toy. May say “Thank you,” “Your turn,” etc.

Complex exchange

Attempting to/returning the toy that has been accepted AND manipulated/labeled BY extending toy to the play partner. This is coded for the person offering to return the toy. If it is a continuing complex exchange (with the same toy) keep coding as an exchange, not a new offer.

Shows a toy

Showing play partner a toy or demonstrating how a toy works BY holding a toy up or out towards the partner while looking at, gesturing, or verbalizing to the play partner; pointing or gesturing towards a toy the partner is not holding while looking at or verbalizing to the partner; pointing out the features of a toy; showing how a toy works; showing the partner an action with a toy while calling the partner’s attention to the toy. Offering play partner a toy BY handing a toy towards the partner (within arms reach); rearranging or setting toy down in front of the partner or on play partner’s lap; throwing or kicking a ball directly to the partner. May or may not release the toy if play partner tries to accept the toy. Taking a toy from the play partner that the partner had not offered. Taking back an unoffered toy that the play partner had previously accepted or taken. Pulling back toy play partner tries to accept after offer or show.

Offers a toy

Takes a toy Retakes Retracts a toy

calculated in a manner similar to Smith et al. (1996). First, the proportion of events in which mothers coordinated interactions with their infants by returning toys was calculated and labeled maternal coordinations. This measure represents the total frequency of maternal toy returns and complex exchanges divided by the total frequency of infant initiations. Infant coordinations were computed as the proportion of events in which infants coordinated

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interactions with their mothers by returning toys, or the total frequency of infant toy returns and complex exchanges divided by the total frequency of maternal initiations. Next, the proportion of events that were directed by the mother was calculated and labeled maternal directing. A composite of the directing behaviors (offer, show, take, retake, retract) was computed for both mothers and infants, and a total of these behaviors for the dyad was calculated. The proportion of events led by the mother was then calculated by dividing the total frequency of maternal directing behaviors (offer, show, take, retake, retract) by the total frequency of directing behaviors for the dyad. 2.4. Training and reliability Research assistants were trained in administering the Bayley MDI prior to data collection. They observed and scored tapes of others administering the Bayley. Their scores were then compared with those of a previously trained tester. They also were videotaped while administering the Bayley to five pilot-study babies, and a previously trained tester scored the videotapes. A criterion of 95% agreement was met by all testers. All Bayley testing was videotaped, and accuracy of testing was checked for a selected set of tapes from both samples. At 11 months (n ⫽ 30), item- by-item percentage agreement was 89%, Kappa was 0.89, and interrater intraclass r was 0.85. At 14 months (n ⫽ 26, Sample I), item-by-item percentage agreement was 93%, Kappa was 0.91, and interrater intraclass r was 0.89. At 14 months (n ⫽ 37, Sample II), item-by-item percentage agreement was 93%, Kappa was 0.94, and interrater intraclass r was 0.88. At 17 months (n ⫽ 26), item-by-item percentage agreement was 93%, Kappa was 0.94, and interrater intraclass r was 0.96. Two coders were trained to code the frequency of social toy play behaviors by practicing with videotapes of pilot-study participants to establish reliability. A criterion of 90% or higher incident-by-incident inter-rater agreement between coders was established prior to coding data. Accuracy of coding social toy play in this study was maintained by checking every fourth videotape (n ⫽ 67), with incident-by-incident agreement of 99% at 11 months, 93% at 14 months (Sample I), 96% at 14 months (Sample II), and 92% at 17 months. Kappa could not be calculated for this measure because there were often more than one code per interval, so chance or expected agreement could not be calculated.

3. Results 3.1. Developmental changes and stability in social toy play Table 2 presents descriptive statistics and tests of stability and change1 for mother-infant social toy play and infant language at 11 and 14 months in Sample I. Stability was assessed with correlation coefficients, change was assessed using paired t tests. Table 3 presents descriptive statistics and tests of stability and change for mother-infant social toy play and infant language at 14 and 17 months in Sample II. From 11 to 14 months, there were statistically significant increases in the frequency of infant social toy play behaviors, with the frequency of initiations, responses, and manipu-

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Table 2 Stability and change in language and social toy play from 11 to 14 months in sample I Descriptives a

b

11 months

Infant behaviors Initiations Responses Manipulations/labels Coordinations Maternal behaviors Initiations Responses Manipulations/labels Coordinations Maternal directing Infant language

14 months M

(SD)

Stability

Change

11 to 14

11 to 14

r

t

M

(SD)

6.12 2.72 2.32 0.05

(5.68) (3.28) (2.86) (0.13)

9.48 5.51 3.93 0.10

(7.24) (7.07) (4.67) (0.20)

.27* .45** .48** .19

3.80** 3.35** 2.90** 1.54

4.01 2.46 0.41 0.06 0.39 7.05c

(5.04) (3.96) (1.15) (0.15 (0.03) (2.04)

10.17 5.90 1.89 0.11 0.41 7.94d

(14.69) (6.55) (3.35) (0.14) (0.31) (2.05)

.41** .36** .34** .30* .24 .21*

3.39** 4.60** 3.77** 2.30* 0.54 —e

n ⫽ 82 for 11-month social toy play. n ⫽ 81 for 14-month social toy play. c n ⫽ 97 for 11-month infant language. d n ⫽ 86 for 14-month infant language. e Raw language scores are not comparable across ages. * p ⬍ .05. ** p ⬍ .01.

a

b

lations/labels increasing over time. This trend is also apparent for maternal involvement in social toy play, with the largest increases in the frequencies of mother initiations and responses. The proportion of maternal coordinations with infant initiations increased from 11 to 14 months, while the proportion of maternal directing did not. Although social toy play behaviors increased in frequency, both mother and infant social toy play behaviors were stable from 11 to 14 months, as indicated by moderate to large stability coefficients. Mothers and infants who were more involved in social toy play at 11 months tended to be more involved at 14 months, as indicated by stability in initiations, responses, and manipulations/labels. Maternal coordinations were stable, but infant coordinations were not. A similar pattern of social toy play development is seen from 14 to 17 months. From 14 to 17 months, both mothers and infants tended to increase the frequency of initiations, responses, and manipulations/labels, although not all of the change coefficients were statistically significant. The proportions of maternal and infant coordinations and maternal directing were similar at 14 and 17 months. Both mother and infant involvement in social toy play were stable from 14 to 17 months, as evidenced by stability coefficients for initiations, responses, and manipulations/labels. 3.2. Relations between mother and infant social toy play and infant language Table 4 displays concurrent and lagged associations between mother-infant social toy play and infant language scores at 11 and 14 months. The frequency of maternal responses and

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Table 3 Stability and change in language and social toy play from 14 to 17 months in sample II Descriptives a

b

14 months

Infant behaviors Initiations Responses Manipulations/labels Coordinations Maternal behaviors Initiations Responses Manipulations/labels Coordinations Maternal directing Infant language

17 months

Stability

Change

14 to 17

14 to 17

M

(SD)

M

(SD)

r

t

6.91 5.94 4.36 0.14

(5.04) (5.66) (4.03) (0.19)

9.78 6.79 5.03 0.12

(6.61) (5.24) (3.90) (0.22)

.29* .52** .48** .07

2.96** 1.15 0.96 ⫺0.41

6.19 4.77 2.22 0.20 0.44 6.75c

(6.12) (4.92) (3.15) (0.24) (0.28) (1.67)

7.13 7.15 2.54 0.15 0.40 7.52d

(6.09) (6.66) (3.16) (0.18) (0.26) (3.51)

.30* .47** .39** .22 .22 .27*

0.65 2.71** 0.55 ⫺1.51 ⫺1.16 —e

n ⫽ 68 for 14-month social toy play. n ⫽ 68 for 17-month social toy play. c n ⫽ 80 for 14-month infant language. d n ⫽ 60 for 17-month infant language. e Raw language scores are not comparable across ages * p ⬍ .05. ** p ⬍ .01.

a

b

manipulations/labels, as well as the proportion of maternal coordinations at 11 months were associated with 14-month infant language. There is a similar lagged association between the frequency of infant responses and manipulations/labels at 11 months and infant language at 14 months. There were small concurrent associations between social toy play and language at 14 months in Sample I. The strongest concurrent associations were for mother and infant responses and manipulations/labels with infant language at 14 months. Table 5 displays concurrent and lagged associations between mother-infant social toy play and infant language scores at 14 and 17 months in Sample II. There were similarities between the 14-month concurrent associations in Sample I and Sample II. The strongest concurrent associations were again for mother and infant responses and manipulations/labels with infant language at 14 months. The strongest lagged association was between maternal coordinations at 14 months and infant language at 17 months. The strongest concurrent association at 17 months was for maternal and infant initiations with infant language. There were similarities between the two samples in patterns of associations. Concurrent associations at 11, 14, and 17 months were small and generally not statistically significant. The strongest patterns were the lagged influences of maternal social toy play behaviors on later infant language. 3.3. Regression and path analysis Path models were constructed to test the effects of mother-infant social toy play on infant language, based on a theoretical model suggesting that specific maternal responses to infant

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Table 4 Concurrent and predictive correlations between frequency of social toy play and language scores at 11 and 14 months in Sample I Social toy play variables 11-month social toy play Infant behaviors Initiations Responses Manipulations/labels Coordinations Maternal behaviors Initiations Responses Manipulations/labels Coordinations Maternal directing Social toy play variables 14-month social toy play Infant behaviors Initiations Responses Manipulations/labels Coordinations Maternal behaviors Initiations Responses Manipulations/labels Coordinations Maternal directing

Language 11a

.04 .09 .13 .04

Language 14b

.16 .26* .27* .05

.07 .10 .16 .20 ⫺.06

.15 .27* .32** .30* .03

Language 11

Language 14c

.14 .22* .21 .06 .12 .21 .15 .10 .09

n ⫽ 79. n ⫽ 70. c n ⫽ 80. * p ⬍ .05. ** p ⬍ .01. a

b

play uniquely influence infant language. Mother-infant play becomes increasingly reciprocal as infants get older, with maternal behaviors ranging from simply accepting a toy to facilitating more complex interchanges in which they manipulate or label the toy and then return it back to the infant. Three models were constructed for each sample, including both mother and infant behaviors at two time points. These models tested the concurrent and predictive associations of maternal responses, manipulations/labels, and coordinations during social toy play with infant language as the final outcome variable. By statistically controlling for the effects of infant initiations with toys, all three models examined the unique influences of maternal play behaviors on infant language, and also examined consistency in play behaviors when accounting for the play partners’ behaviors. These three models were compared for each sample.2 In each model, the configurations were the same, but the measures of social toy play used in each model were maternal responses, manipulations/ labels, and coordinations, in models 1, 2, and 3 respectively. In the 11- to 14-month sample, the first two models, with maternal responses and maternal manipulations/labels, explained

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Table 5 Concurrent and predictive correlations between frequency of social toy play and language scores at 14 and 17 months in Sample II Social toy play variables 14-month social toy play Infant behaviors Initiations Responses Manipulations/labels Coordinations Maternal behaviors Initiations Responses Manipulations/labels Coordinations Maternal directing Social toy play variables 17-month social toy play Infant behaviors Initiations Responses Manipulations/labels Coordinations Maternal behaviors Initiations Responses Manipulations/labels Coordinations Maternal directing

Language 14a

Language 17b

.01 .17 .17 .16

.08 .01 .04 .13

.06 .25* .24* .20 ⫺.01

⫺.14 .17 .16 .36** ⫺.21

Language 14

Language 17c

.17 .13 ⫺.03 ⫺.05 .21 .10 ⫺.07 .05 .00

n ⫽ 68. n ⫽ 51. c n ⫽ 59. * p ⬍ .05. ** p ⬍ .01. a

b

the most variance in infant language. In the 14- to 17-month sample, the third model, with maternal coordinations, explained the most variance in infant language. In the 11- to 14-month sample, Models 1 and 2 examined the unique influences of maternal responses and maternal manipulations/labels on infant language at both 11 and 14 months (see Figs. 1 and 2). Model 1 tested the relative contributions of maternal responses and infant initiations at 11 months and 14 months to infant language at 11 and 14 months. Maternal responses refer to accepting or acknowledging toys offered by the infant and may or may not include gestures or language specific to the object, such as manipulations or labels. In order to test the hypothesis that one important component of coordinated interactions is the amount of object manipulations and labels included in those interactions, a second model was constructed. Model 2 tested the association between maternal manipulations/labels and infant initiations at 11 and 14 months with 11- and 14-month infant language (see Table 6).

L.A. Newland et al. / Infant Behavior & Development 24 (2001) 1–25

Fig. 1. Path Model 1 from 11 to 14 months; Maternal Responses

Fig. 2. Path Model 2 from 11 to 14 months; Maternal Manipulations/Labels

15

16

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Table 6 Summary of regression analysis examining the predictors of language scores from 11 to 14 months in sample I

␤

Variables entereda Path Model 1 Dependent variable Language 11 Predictors Infant initiations 11 Maternal responses 11 Dependent variable Infant initiations 14 Predictors Infant initiations 11 Maternal responses 14 Dependent variable Maternal responses 14 Predictors Infant initiations 11 Maternal responses 11 Dependent variable Language 14 Predictors Language 11 Infant initiations 11 Maternal responses 11 Infant initiations 14 Maternal responses 14 Path Model 2 Dependent variable Language 11 Predictors Infant initiations 11 Maternal manipulations/labels Dependent variable Infant initiations 14 Predictors Infant initiations 11 Maternal manipulations/labels Dependent variable Maternal manipulations/labels Predictors Infant initiations 11 Maternal manipulations/labels Dependent variable Language 14 Predictors Language 11 Infant initiations 11 Maternal manipulations/labels Infant initiations 14 Maternal manipulations/labels n ⫽ 70. * p ⬍ .05. ** p ⬍ .01. a

⫺.07 .15

.12 .21

.04 .33

.17 ⫺.17 .43 ⫺.22 .24

11

11

R2

t

⫺.08 .21

.24 .06

11 14

.05 .32

.12 ⫺.03 .40 .07 ⫺.06

.01

.43

.09

3.26*

.13

4.83**

.17

2.45*

.03

1.21

.07

2.54

.12

4.15*

.17

2.41*

⫺.41 .86

.68 1.23

.25 1.99*

1.46 ⫺1.03 2.54** ⫺.81 .86

⫺.59 1.51

1.76 .43

14 11

F

.34 2.37*

.94 ⫺.25 2.91** .45 ⫺.38

L.A. Newland et al. / Infant Behavior & Development 24 (2001) 1–25

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In Model 1 and Model 2, both controlling statistically for infant initiations, there was stability in maternal play behaviors. There was less stability in infant initiations from 11 to 14 months, when controlling for maternal play behaviors at 11 months. This is in line with the theoretical assumption, that infants begin initiating interactions with toys more frequently across the second year, so it was expected that there would be less stability before 14 months than after. Both Model 1 and Model 2 predicted 14-month language, but not 11-month language. With 11-and 14-month social toy play included, the path between 11- and 14- month language was not statistically significant in either Model 1 or Model 2. In addition, infant behaviors at 11 and 14 months and maternal behavior at 14 months did not have statistically significant paths to infant language at 14 months. The strongest path predicting 14-month language was a lagged effect from 11-month maternal behaviors. For both Models 1 and 2, 11- and 14- month maternal and infant play variables explained about 17% of the variance in infant language at 14 months. In addition, the path coefficients from 11-month maternal behaviors to 14-month infant language were very similar in both models. Thus, in contrast to our expectations, at 11 and 14 months the model using maternal manipulations/labels was not better at explaining infant language than the model using maternal responses. Model 3, including maternal coordinations at 11 and 14 months, was not statistically significant in predicting infant language at either 11 or 14 months and is not described further. In the 14- to 17-month sample, Models 1 and 2 were tested but were not good predictors of infant language at either 14 or 17 months, with nonsignificant paths and small R2 values. In line with theoretical assumptions, Model 3 (see Fig. 3) was constructed to examine the unique influence of maternal coordinations at 14 and 17 months on Infant Language at 14 and 17 months (see Table 7). Model 3 supported the theoretical proposition that maternal coordinations with infants would be a better predictor of infant language at 17 months than maternal responses and manipulations/labels. In Model 3 there was less stability in maternal play behaviors, when controlling statistically for infant initiations, and the path from infant initiations was a stronger predictor of later maternal coordinations than the path from earlier maternal coordinations. Unlike in the younger sample, in this 14- to 17-month sample there was stability in the frequency of infant Initiations, when controlling for maternal play behaviors at 14 months. Thus, whereas the path coefficients from 11- to 14-month infant Initiations were not statistically significant, the path coefficient from 14- to 17-month infant Initiations in Model 3 was statistically significant. This is in line with the theoretical assumption that infants are increasing their initiation of and participation in social play interactions. Mothers and infants appear to be making a shift towards greater infant initiations in play, with infant initiations exerting a stronger bi-directional influence on maternal coordinations. In the 14- to 17-month sample, Model 3 looked similar to the models from the younger sample (Figs. 1 and 2), with the strongest path being the lagged influence of earlier maternal play behaviors on later infant language. The concurrent paths predicting language in the 14- to 17-month sample were still quite small, as in the 11- to 14-month sample. The path from 14-month infant language to 17-month infant language was not

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Fig. 3. Path Model 3 from 14 to 17 months; Maternal Coordinations

statistically significant when controlling statistically for 14- and 17-month play behaviors. The strongest path predicting 17-month Infant Language was a lagged effect from 14-month maternal coordinations.

4. Discussion This study investigated developmental changes in mother-infant toy play and the associations between mother-infant toy play and infant language. The results indicated specific developmental trends evident in maternal and infant social toy play behaviors, with infants increasing initiations in play and mothers increasing turn-taking by coordinating interactions with their infants. These developmental trends were related to infant language acquisition, with both concurrent and later effects of mother-infant toy play on language development. Indeed, specific patterns over time suggest that maternal behaviors during social toy play influence infant language development both immediately and at later time points. One objective of this study was to identify stability and change in social toy play behaviors. This study showed stability in mother-infant play patterns, indicating that early play interactions “set the stage” for later social toy play. This result is similar to other studies of mother-infant interactions, that have found stability in mother-infant play patterns over time (Bornstein & Tamis-LeMonda, 1990; Messinger & Fogel, 1998; Tamis-LeMonda & Bornstein, 1991). In addition, there was greater stability in the amount of interactions

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Table 7 Summary of regression analysis examining the predictors of language scores from 14 to 17 months in sample II

␤

Variables entereda Path Model 3 Dependent variable Language 14 Predictors Infant initiations 14 Maternal coordinations Dependent variable Infant initiations 17 Predictors Infant initiations 14 Maternal coordinations Dependent variable Maternal coordinations Predictors Infant initiations 14 Maternal coordinations Dependent variable Language 17 Predictors Language 14 Infant initiations 14 Maternal coordinations Infant initiations 17 Maternal coordinations

14

14

t

.03 .20

.29 ⫺.01

14 17

.29 .22

.19 .06 .34 .09 ⫺.07

F

.04

1.44

.08

2.10

.13

3.51*

.19

2.00

.23 1.68

2.05* ⫺.10

17 14

R2

2.12* 1.61

1.31 .39 2.29* .58 ⫺.45

n ⫽ 51. * p ⬍ .05. ** p ⬍ .01. a

initiated by infants from 14 to 17 months than from 11 to 14 months, suggesting that some infant behaviors are becoming more stable across time. Changes in mother-infant play behaviors over time indicated that both mothers and infants increased their involvement in social toy play over time. Infants in this study increasingly initiated social toy play, and mothers increasingly responded by coordinating their actions with the infant. This is consistent with past studies showing that infants increasingly initiate and manage coordinated interactions with mothers during this same developmental period (Messinger & Fogel, 1998; Mosier & Rogoff, 1994). In contrast, mothers in this study did not direct their infants’ attention more frequently over time, a finding consistent with past studies showing that towards the end of the first year, mothers increase the frequency of attention-maintaining behaviors during toy play (such as coordinated interactions), but do not increase the frequency of attention-directing behaviors (Smith et al., 1996). The second objective of this study was to examine relations between mother-infant social toy play and infant language development. Generally, maternal play behaviors were related to infant language, but specific play behaviors were related differently at different ages. Maternal responses to infant initiations and maternal manipulation and labeling of objects offered by the infant at 11 months were associated with greater infant language capacity at 14 months. By 14 months, when the infants had become more capable of engaging in

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coordinated interactions, maternal coordinations had the strongest lagged effect on later infant language, underscoring the importance of joint attention during joint play interactions. Other studies have found that both socially coordinated behaviors and shared attention to objects at 14 months are related to later language development and that mothers who respond to their infant’s focus of attention are supporting the acquisition of infant language (Dunham & Dunham, 1995; Hustedt & Raver, 1998; Laasko et al., 1999). Maternal directive behaviors were not associated with infant language in the present study, but coordinations that maintained infant attention were associated with language at 14 and 17 months. In other research, early maternal stimulation has been associated with language development at the end of the first year (Tamis-LeMonda & Bornstein, 1989). By 14 months, however, extending infant object actions by modeling new activities or elaborating on the ongoing activity is more closely associated with later language than either maintaining or redirecting infant attention towards toys (Laasko et al., 1999). Because infants are just developing the ability to coordinate interactions with others at the end of the first year, a shift from maternal directing to responding and extending may be important for language acquisition in the second year. The third objective was to assess the unique and combined contributions of maternal and infant social toy behaviors, at specific age points, to infant language development. Although previous studies have shown that reciprocal mother-infant interactions occur from very early in infancy and are related to later infant play and language (Bornstein &Tamis-LeMonda, 1990; Tamis-LeMonda & Bornstein, 1989), our results suggest a developmental shift toward more frequent infant initiation of these interactions and towards increasingly reciprocal maternal responses. This study and others indicate that maternal responses shift along with infant developmental changes, and this shift appears to be related in specific ways to language acquisition (Laasko et al., 1999). Coordinated actions with objects, within familiar routines, help infants establish shared meanings that facilitate language learning (Bruner, 1977, 1983). The pragmatics of language involve turn taking and reciprocity of action and meaning. Coordinations with objects, in which one person offers an object, the other takes it and then subsequently returns it, represent both the structure and function of a conversation, even if no language is used. In early interactions between adults and infants, there are alternations of turn taking involving simple behaviors such as looking, nonverbal vocalizing, expressions and gestures. These alternations of verbal and nonverbal behaviors demonstrate the same timing and rhythm as conversations and have been referred to as “conversation” (Bateson, 1975) or dialogue (Kaye, 1977), both in a metaphorical sense as well as in a more literal sense in which these turn-taking alternations are the precursors to later verbal communication (Bloom, Russell & Wassenburg, 1987; Kaye, 1982). There is evidence that maternal verbal and nonverbal vocal behaviors are structured in such a way as to maintain a “conversational chain” (Hayes, 1984). What is missing in these early nonverbal turn-taking alternations is a topic of conversation, a referent, an object of common interest and attention. By integrating objects into nonverbal “conversations,” that is by exchanging actual objects back and forth, mothers and toddlers are taking the first step toward what will eventually become actual verbal conversation about an object. Indeed, the mother is maintaining the “conversation” not just by accepting the object, but also by returning it back to the infant, perhaps after an action or word is expressed.

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The complexity of this exchange is what offers support for the infant’s beginning understanding of object labels in conversational context. 4.1. Limitations and strengths of this study Although coordinated interactions between mothers and infants became increasingly important in this study, the effect sizes were small, perhaps because the infants’ joint attention skills are just developing towards the end of the first year (Adamson & Bakeman, 1985; Carpenter et al., 1998). Coordinated interactions may have stronger effects on language later in the second year when infant joint attention is increasing in duration and frequency. Future research should investigate joint attention within coordinated interactions with toys, and examine relations between these kinds of interactions and language through the second year. Methodological constraints in this study may limit the generalizability of findings. One limitation of this study is the lack of longitudinal data at all three time points. The cross-sequential design used in this study was more feasible, but ideally, a single-cohort longitudinal design would allow for developmental comparisons across multiple time points. Another limitation in study was the low frequency of some behaviors, but there is both theoretical and empirical support for the low frequency of some behaviors at 11 months (such as infant coordinations) with an increase in frequency as infants become more reciprocal in their interactions (Bruner, 1977). A third limitation that restricts the generalizability of the results is the relatively brief duration of the laboratory observations. However, these observations were structured to be similar to other situations that mothers and infants encounter in daily activities, such as when they are required to wait in a waiting room. Although the structured laboratory setting may limit the ecological validity of the results, standardized instructions, types of toys available, length of observations, and location of the observations increased both the likelihood that the target behaviors would occur and the reliability of coding those behaviors (Leyendecker et al., 1997). In addition, the likelihood of interruptions and distractions that would vary from home to home were reduced in the laboratory setting, which strengthened the internal validity of the study (Pedhazur & Schmelkin, 1991; Roggman, Boyce & Newland, 2000). The intent of this study was to conduct initial explorations of the mother-infant interaction correlates of early language in a controlled setting. Further research should extend these results to naturalistic settings with longer observation periods to increase the ecological validity of the findings from this study. This study had several strengths, including the testing of theoretical links between two domains, the use of two cohorts to span a wider age range, and the specificity of the measures and models. Based on the results from the path models tested in this study, a conceptual framework can be constructed. The framework proposed in Fig. 4 includes the bidirectional influences over time of mothers and infants on social toy play and language. This framework could be used to guide future research examining mother-infant social toy play and its effects on infant language development. An important implication of this study is the replication and extension of other research indicating that specific maternal behaviors influence child language acquisition during specific periods of development (Barratt & Roach, 1999; Baumwell et al., 1997; Bruner,

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Fig. 4. Conceptual Model of Mother and Infant Contributions to Language from 11 to 17 months

1977, 1983; Carpenter et al., 1998; Dunham & Dunham, 1995; Laasko et al., 1999; Tomasello & Farrar, 1986). These results have implications for intervention and practice, especially since maternal sensitivity and responsiveness are more critical for children who are less verbally advanced (Baumwell et al., 1997). Our data indicate that responsiveness by mothers to infant behaviors is more important in the 11- to 14-month period, while more reciprocal interactions involving turn taking become important in the 14- to 17-month period. The proposed framework in this study provides a model for parents and early interventionists concerned with promoting language development for children “at-risk” and those with language delays. Our results support a model in which language acquisition is facilitated by social toy play interactions that are both responsive to infant initiations and adaptive to infant development.

Notes 1. Although some of these measures had skewed distributions because of zero scores, analyses without those cases were virtually identical and the statistical tests used are generally robust with regard to non-normal distributions 2. The assumptions of multiple regression indicate that the Y scores should be normally distributed (as the language scores in this study are) but does not demand that the predictors should be normally distributed (several of which are skewed) (Glass & Hopkins, 1996).

Acknowledgments The authors wish to thank the mothers and infants who participated in this research. We also thank the research assistants who helped with this project, including Emily Call, Lori

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Lund and Wade Taylor for assistance with observational coding, and Andrea Hart, Miriam Jennings, Sondra Moe, Teri Morrison, Kris Rasmussen, and Vonda Jump for assistance with data collection. We also thank Diana Coyl for comments and assistance reviewing earlier drafts, and Chih Ying Chang for assistance with manuscript preparation. This research was conducted in partial fulfillment of the Doctoral requirements for Lisa A. Newland.

References Adamson, L. B., & Bakeman, R. (1985). Affect and attention: Infants observed with mothers and peers. Child Development, 56, 582–593. Bakeman, R., & Adamson, L. (1984). Coordinating attention to people and objects in mother-infant and peer-infant interaction. Child Development, 55, 1278 –1289. Barratt, M. S., & Roach, M. A. (1999, April). Contextual limits on mother-infant conversation. Paper presented at the Biennial Meeting of the Society for Research in Child development, Albuquerque, NM. Bateson, M. C. (1975). Mother-infant exchanges: The epigenesis of conversation interaction. Annals of the New York Academy of Science, 263, 101–113. Baumwell, L., Tamis-LeMonda, C. S., & Bornstein, M. H. (1997). Maternal verbal sensitivity and child language comprehension. Infant Behavior and Development, 20(2), 247–258. Bayley, N. (1969). Bayley Scales of Infant Development. New York: Psychological Corporation. Bee, H. L., Barnard, K. E., Eyres, S. J., Gray, C. A., Hammond, M. A., Spietz, A. L., Snyder, C., & Clark, B. (1982). Prediction of IQ and language skill from perinatal status, child performance, family characteristics, and mother-infant interactions. Child Development, 53, 1134 –1156. Bloom, L. (1993). The transition from infancy to language: Acquiring the power of expression. New York: Cambridge University Press. Bloom, K., Russell, A., &, & Wassenburg, K. (1987). Turn taking affects the quality of infant vocalizations. Journal of Child Language, 14, 211–227. Bornstein, M. H., Haynes, O. M., O’Reilly, A. W., & Painter, K. M. (1996). Solitary and collaborative pretense play in early childhood: Sources of individual variation in the development of representational competence. Child Development, 67, 2910 –2929. Bornstein, M. H., & Tamis-LeMonda, C. S. (1990). Activities and interactions of mothers and their firstborn infants in the first six months of life: Covariation, stability, continuity, correspondence, and prediction. Child Development, 61, 1206 –1217. Bruner, J. S. (1977). Early social interaction and language acquisition. In H. R. Schaffer (Ed.), Studies in mother-infant interaction (pp. 271–289). New York: Academic. Bruner, J. S. (1983). Child’s talk: Learning to use language. New York: Norton. Carpenter, M., Nagell, K., & Tomasello, M. (1998). Social cognition, joint attention, and communicative competence from 9 to 15 months of age. Monographs of the Society for Research in Child Development, 63(no. 255). Dunham, P., & Dunham, R. (1992). Lexical development during middle infancy: A mutually driven infantcaregiver process. Developmental Psychology, 28, 414 – 420. Dunham, P. J., & Dunham, F. (1995). Optimal social structures and adaptive infant development. In C. Moore and P. J. Dunham (Eds.) Joint attention: Its origin and role in development (p.159 –188). Hillsdale, NJ: Lawrence Erlbaum Associates. Dunham, P. J., & Moore, C. (1995). Current themes in research on joint attention. In C. Moore and P. J. Dunham (Eds.) Joint attention: Its origin and role in development (p.15–28). Hillsdale, NJ: Lawrence Erlbaum Associates. Glass, G. V., & Hopkins, K. D. (1996). Statistical methods in education and psychology (3rd ed). Needham Heights, MA: Allyn and Bacon.

24

L.A. Newland et al. / Infant Behavior & Development 24 (2001) 1–25

Hart, B., & Risley, T. R. (1995). Meaningful differences in the everyday experience of young American children. Baltimore, MD: Paul H. Brookes Pub. Hayes, L. A. (1984). Interaction, engagement, and the origins and growth of communication: Some constructive concerns. In L. Feagans, C. Garvey, & R. Golinkoff (Eds.), The.origins and growth of communications (pp. 136 –161). Norwood, N. J.: Ablex. Hollingshead, A. B. (1975). The four factor index of social status. Unpublished manuscript, Yale University. (Available from A. B. Hollingshead, Department of Sociology, Yale University, New Haven, CT 06520). Hustedt, J. T., & Raver, C. C. (1998, April). Scaffolding in low-income mother-child dyads: Relations with joint attention and reciprocity. Poster presented at the International Conference on Infant Studies, Atlanta, GA. Karrass, J., Mullins, J., & Burke, J. E. (1999, April). Infant temperament and maternal encouragement of attention as predictors of early language development. Paper presented at the Biennial Meeting of the Society for Research in Child development, Albuquerque, NM. Kaye, K. (1977). Toward the origin of dialogue. In H. R. Schaffer (Ed.), Studies in mother-infant interaction (pp. 89 –118). New York: Academic Press. Kaye, K. (1982). The mental and social life of babies. Chicago, IL: University of Chicago Press. Laasko, M. L., Poikkeus, A. M., Eklund, K., & Lyytinen, P. (1999). Social interactional behaviors and symbolic play competence as predictors of language development and their associations with maternal attentiondirecting strategies. Infant Behavior and Development, 22, 541–556. Landry, S. H., Garner, P. W., Swank, P. R., & Baldwin, C. D. (1996). Effects of maternal scaffolding during joint toy play with preterm and full-term infants. Merrill Palmer Quarterly, 42(2), 177–199. Leevers, H. J., & Chelius, L. (1999, April). Gestures to familiar, novel, and placeholder objects and language, imitation, and cognition at 12, 16, and 24 months. Paper presented at the Biennial Meeting of the Society for Research in Child development, Albuquerque, NM. Leyendecker, B., Lamb, M. E., & Scho¨ lmerich, A. (1997). Contexts as moderators of observed interactions: A study of Costa Rican mothers and infants from differing socioeconomic backgrounds. International Journal of Behavioral Development, 21, 15–34. Messinger, D. S., & Fogel, A. (1998). Give and take: The development of conventional infant gestures. Merrill-Palmer Quarterly, 44, 566 –590. Mosier, C. E., & Rogoff, B. (1994). Infants’ instrumental use of their mothers to achieve their goals. Child Development, 65, 70 –79. Mundy, P., & Gomes, A. (1998). Individual differences in joint attention skill development in the second year. Infant Behavior and Development, 21(3), 469 – 482. Pedhazur, E. J., & Schmelkin, L. P. (1991). Measurement, design, and analysis: An integrated approach. Lawrence Erlbaum: Hillsdale, NJ. Reissland, N. (1998). Context dependency in parental speech. British Journal of Developmental Psychology, 16, 365–373. Reznick, J. S., Corley, R., & Robinson, J. (1997). A longitudinal twin study of intelligence in the second year. Monographs of the Society for Research in Child Development, 62, serial no. 249, 1–160. Roggman, L. A., Boyce, L. K., & Newland, L. A. (2000). Assessing mother-infant interaction in play. In C. E. Schaefer, K. Kitlin, & A. Sandgrund (Eds.), Play diagnosis and assessment: 2 nd Edition. New York: Wiley. Roggman, L., Langlois, J., & Hubbs-Tait, L. (1987). Mothers, infants, and toys: Social play correlates of attachment. Infant Behavior and Development, 10, 233–237. Rollins, P. R., Marchman, V. A., & Mehta, J. (1998, April). Infant gaze following, joint attention, and vocabulary development. Poster presented at the International Conference on Infant Studies, Atlanta, GA. Ruddy, M. G., & Bornstein, M. H. (1982). Cognitive correlates of infant attention and maternal stimulation over the first years of life. Child Development, 53, 183–188. Saxon, T. F. (1997). The relationship between maternal following or switching verbal references to objects and infant language competence. Poster presented at the biennial meeting of the Society for Research in Child Development, Washington, D.C. Scho¨ lmerich, A., Lamb, M. E., Leyendecker, B., & Fracasso, M. P. (1997). Mother-infant teaching interactions

L.A. Newland et al. / Infant Behavior & Development 24 (2001) 1–25

25

and attachment security in Euro-American and Central American immigrant families. Infant Behavior and Development, 20, 165–174. Smith, K. E., Landry, S. H., Swank, P. R., Baldwin, C. D., Denson, S. E., & Wildin, S. (1996). The relation of medical risk and maternal stimulation with preterm infants’ development of cognitive, language, and daily living skills. Journal of Child Psychology and Psychiatry and Allied Disciplines, 37, 855– 864. Spencer, P. E., & Meadow-Orlans, K. P. (1996). Play, language, and maternal responsiveness: A longitudinal study of deaf and hearing infants. Child Development, 67, 3176 –3191. Tamis-LeMonda, C., & Bornstein, M. (1989). Habituation and maternal encouragement of attention in infancy as predictors of toddler language, play, and representational competence. Child Development, 60, 738 –751. Tamis-LeMonda, C., & Bornstein, M. (1991). Individual variation, correspondence, stability, and change in mother and toddler play. Infant Behavior and Development, 14, 143–162. Tamis-LeMonda, C., & Bornstein, M. (1994). Specificity in mother-toddler language-play relations across the second year. Developmental Psychology, 30, 283–292. Tomasello, M. (1990). The role of joint attentional processes in early language development. Language Sciences, 10, 68 – 88. Tomasello, M. (1995). Joint attention as social cognition. In C. Moore and P. J. Dunham (Eds.), Joint attention: Its origin and role in development (p.103–130). Hillsdale, NJ: Lawrence Erlbaum Associates. Tomasello, M., & Farrar, M. (1986). Joint attention and early language. Child Development, 57, 1454 –1463. Vibbert, M., & Bornstein, M. H. (1989). Specific associations between domains of mother-child interaction and toddler referential language and pretense play. Infant Behavior and Development, 12, 163–184.