The Association Between Intention Understanding ...

Empirical Article

The Association Between Intention Understanding and Peer Cooperation in Toddlers Sabine Hunnius, Harold Bekkering, and Antonius H. N. Cillessen This study examined whether 19-month-old infants’ social understanding was related to their interaction behavior during dyadic cooperation with a peer. Toddlers’ ability to predict others’ action intentions was examined using a computerized experimental task. The children watched a series of stimulus movies in which an actor expressed her liking or disliking towards two different objects and then announced that she was going to grasp one of them. Toddlers’ eye movements were registered, and it was examined whether they showed anticipatory looks to the object the model was going to grasp. During the dyadic cooperation task the toddlers interacted with an unfamiliar peer. Toddlers’ interaction performance during cooperation was observed, and affiliative and antagonistic behaviors were coded. Intention understanding was positively correlated with affiliative behaviors, and negatively with antagonistic behaviors during the cooperation task. Measures of cooperation success were not related to toddlers’ intention understanding. Toddlers’ capability to understand others’ intentions was thus closely associated with their peer interaction behavior, but not with their task performance. Keywords: cooperation, peer interaction, intention understanding, infancy

In recent years, extensive research has been conducted on the emergence and development of social-cognitive skills in early childhood, such as gaze and face perception or intention and action understanding (e.g., Corkum & Moore, 1995; Leppänen & Nelson, 2009; Meltzoff, 1995; Woodward, 1998). These early social-cognitive competencies are likely to play an important role in children’s social development and in the emergence of peer interaction patterns. Several studies have shown that competences in the areas of intention understanding or joint attention during infancy are related to the later development of theory of mind skills (Aschersleben, Hofer, & Jovanovic, 2008; Charman et al., 2000; Wellman, Phillips, Dunphy-Lelii, & LaLonde, 2004). To date, however, only few studies have examined whether young children’s social-cognitive abilities are linked to their behavior when interacting with peers (Brownell, Ramani, & Zerwas, 2006; Ensor & Hughes, 2005). To better understand the possible links between social-cognitive and social development, this study examines whether early social understanding is related to the quality of peer interactions in toddlers. Humans are social beings from the first days of their life. Even newborns actively engage in rhythmic face-to-face interactions with their mothers (Brazelton, Tronick, Adamson, Als, & Wise, 1975; Censullo, Lester, & Hoffman, 1985; Murray & Trevarthen, 1986). And although infants’ earliest interactions are usually with an adult caretaker, infants begin to show interest in one another as early as 2 months of age (EckerEuropean Journal of Developmental Science [EJDS]. 2009, Vol. 3, No. 4, 368–388 © Vandenhoeck & Ruprecht 2010, ISSN 1863-3811

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man, 1979; Fogel, 1979). It is not before the end of the first year of life, however, that peer interaction with imitation, toy-directed activities, and brief episodes of social play emerges (Eckerman, 1979; see Brownell & Brown, 1992 and Eckerman & Peterman, 2001, for reviews). From 18 months of age on, infants’ interactions with peers become more frequent and coordinated, and longer periods of peer play begin to occur (Brenner & Mueller, 1982; Bronson, 1981; Eckerman, Whatley, & Kutz, 1975; Ross, 1982). One particularly challenging form of interaction between two persons is cooperation, as it requires that individuals coordinate their actions in time and space to jointly bring about a change in the environment (Sebanz, Bekkering, & Knoblich, 2006). Infants display the motivation to engage in cooperation from early in infancy on and interact with adults in simple games and joint action routines by 12 to 18 months of age (Hay, 1979; Ross & Lollis, 1987; Warneken, Chen, & Tomasello, 2006; see Carpenter, 2009, for a review). The ability to comprehend the concept of a joint action compared to a parallel action, and to successfully coordinate own actions with those of another person, however, develops only around three years of age (Gräfenhain, Behne, Carpenter, & Tomasello, 2009; Meyer, Bekkering, Paulus, & Hunnius, 2009). The ability to cooperate with a peer appears to lag behind the development of cooperation with adult partners: Peer cooperation in a simple task has been observed only incidentally in 18-month-old infants, whereas 24- and 30-month-old children have been shown to coordinate their behavior more quickly and effectively (Brownell & Carriger, 1990). The emergence of cooperative play with peers has been described as a milestone in social development, as it also marks one of the starting points of peer involvement (Brownell et al., 2006; Dunn, 1988; Garvey, 1990; Hartup, 1983, 1996). Before young children make their entry into peer culture, they have been exposed to the social world for a long time and appear to have acquired a number of rather sophisticated social-cognitive skills. From the first days of life, infants observe their environment and the people acting and interacting in it. Recent research demonstrates that infants’ social-cognitive skills undergo rapid development during the first two years of life. As early as 6 months of age, infants have been shown to pay attention to the goals of an action (Woodward, 1998, 1999) and to visually anticipate the goals of an ongoing action they observe (Falck-Ytter, Gredebäck, & von Hofsten, 2006; Hunnius & Bekkering, in press). Towards the end of the first year of life, infants monitor and follow the gaze of other persons (Corkum & Moore, 1995; D’Entremont, Hains, & Muir, 1997), and during the second year of life, their knowledge of looking behavior as a mental act of seeing develops (Brooks & Meltzoff, 2002; Moll & Tomasello, 2004; Moore & Corkum, 1998). From about one year of age, young children also use these attention cues to relate other people’s emotional expressions to objects (Barna & Legerstee, 2005; Phillips, Wellman, & Spelke, 2002; Repacholi, 1998). When 12-month-old infants, for instance, observe a person who looks at and expresses positive emotions about one object but not a second one, they show signs of surprise if they subsequently see the person with the second object (Phillips et al., 2002). Infants thus appear to form expectations about a person’s desires, intentions, and actions on the basis of the emotional expression they observe this person European Journal of Developmental Science [EJDS]. 2009, Vol. 3, No. 4, 368–388 © Vandenhoeck & Ruprecht GmbH & Co. KG, Göttingen 2010, ISSN 1863-3811

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display towards an object. Later during the second year, children’s reasoning about others’ desires develops and they begin to recognize that desires are related to emotions and that others’ desires can be different from their own (Repacholi & Gopnik, 1997). It can be hypothesized that these rapidly developing social-cognitive skills may also play a crucial role in young children’s ability to successfully cooperate with other toddlers. To be able to act jointly with a peer, children need to perceive what their peers are attending to, understand their intentions, and predict their actions. Moreover, early social-cognitive competencies might be essential not only for cooperation success but also for the quality of the interactions with peers (Hay, Payne, & Chadwick, 2004). In harmonious interactions, children correctly interpret the emotional expressions of each other, understand each others’ intentions, and flexibly respond to one another. Although a close relationship between early social-cognitive skills and peer interaction capacities has been suggested (Brownell, 1986; Brownell & Hazen, 1999; Dunn, 1988; Eckerman & Peterman, 2001), evidence for these links is still rare. Therefore, the goal of the present study was to examine whether social-cognitive skills in infants are linked to, on the one hand, the quality of their cooperative behavior with a peer and, on the other hand, their success at completing a task together. It was expected that infants’ understanding of others’ affect and intentions would be related to their behavior during a peer cooperation task and to the chance of successfully completing the task. More specifically, we expected that toddlers who perform better on an intention understanding task would show more affiliative and less antagonistic behaviors during cooperation with a peer and would also be more successful in solving a peer cooperation task. Method Participants

Participants were 52 19-month-old infants (range 18;18 to 19;24 months, mean age 19;4 months, 22 girls). All children were healthy, full-term infants without any preor perinatal complications. They were selected from a sample of families who responded to an invitation letter sent to all families with infants of the appropriate age in the Nijmegen area (a Dutch city with approximately 160.000 inhabitants). Therefore participants were mostly Dutch, exposed mostly to Dutch in the home, and had mixed socioeconomic backgrounds. The parents were informed about the purpose of the study and then signed a consent form. All parents received a baby book or a monetary compensation for their child’s participation in the study. The toddlers were invited to the lab in dyads, as the study consisted of a peer play session in addition to an individual intention understanding task. Whereas all 52 participants provided data for the individual intention understanding task, peer interaction data could be collected for 38 of the toddlers (i.e. 19 dyads). In several cases, the European Journal of Developmental Science [EJDS]. 2009, Vol. 3, No. 4, 368–388 © Vandenhoeck & Ruprecht GmbH & Co. KG, Göttingen 2010, ISSN 1863-3811


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partner peer canceled at short notice or did not show up, or no peer play session could be conducted due fussing, crying, or general inactivity of at least one peer or due to parental involvement. Of the final dataset of 19 peer dyads, 6 consisted of two boys, 5 of two girls, and 8 were mixed-gender dyads. Intention Understanding Task

First, both children separately completed a 5-min computer task. The computer task was used to assess the toddler’s ability to predict other persons’ actions on the basis of perceptual-emotional displays. While their eye movements were registered, toddlers watched a series of stimulus movies in which a female model first expressed her liking or disliking towards two different objects and then said that she was going to grasp one of them (cf. Barna & Legerstee, 2005; Phillips et al., 2002). Earlier studies that used a visual habituation paradigm with comparable stimuli have demonstrated that by 9 to 12 months of age, infants look longer at a stimulus in which a model was holding the object she had previously evaluated in a negative way than at a stimulus in which the model was holding the positively cued object (Barna & Legerstee, 2005). Experimental setup and procedure. During the experiment, the toddler was seated in an infant seat on the lap of his or her parent who was sitting on a chair. All children were tested at a viewing distance of approximately 60 cm. To minimize visual distraction, lights were dimmed during the experiment. Gaze of both eyes was recorded using a corneal reflection eye-tracker (Tobii 1750, Tobii Technology, Stockholm, Sweden). The Tobii eye-tracking system is integrated in a 17” TFT flat-screen monitor on which the stimuli were shown, and it records gaze data at 50 Hz with an average accuracy of 0.5° visual angle. The monitor was mounted on an adjustable arm, so that the screen could always be positioned at the correct distance and fronto-parallel to the child’s face. Prior to testing, the gaze of each child was calibrated. We used a 9-point calibration procedure, in which an expanding-contracting circle accompanied by a sound appeared in every position of a screen-wide 3 x 3 grid of calibration points on a black background. If seven or less points were calibrated successfully, the calibration was repeated for the missing points; otherwise the experiment was started. Before presentation of each stimulus, a short attention getter movie was presented to the toddlers to (re-)direct their gaze to the screen. Stimuli. The stimulus material consisted of five short movies in which a female model who was visible from the waist up stood behind a table with two similar but differently colored objects in front of her. The objects were sponges, plastic wine glasses and cylinders, and they could be either red and blue, orange and pink, or turquoise and pink. One object was laying on the left, the other on the right side of the table. As the model was standing a few steps away from the table, both objects were in her view, but out of her reach. In the first part of the movie, the model expressed positive emotion towards one object and negative emotion towards the other (see Figure 1A for key frames from one stimulus movie). The model displayed the emotions on her face while her gaze was European Journal of Developmental Science [EJDS]. 2009, Vol. 3, No. 4, 368–388 © Vandenhoeck & Ruprecht GmbH & Co. KG, Göttingen 2010, ISSN 1863-3811

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directed towards the object. She also expressed her liking or disliking vocally by saying “This I like” (in Dutch: “Die vind ik leuk”) and “This I do not like” (in Dutch: “Die vind ik niet leuk”). This first part of the movie lasted about 18 seconds. During the second part of the stimulus movie, the model announced that she was going to grasp one of the objects (“I am going to get one!”; in Dutch: “Ik ga er een pakken!”), moved towards the table, and raised her hands. Then, she grasped the object towards which she had previously expressed her liking (see Figure 1B). This second part of the movie lasted about 11 seconds. All versions of the movie had the same duration, and the action steps (e.g., looking at the stimuli, announcing the grasp, moving forward, grasping the object) had approximately the same timing. The model’s looking behavior was also kept constant across stimuli: At the beginning of each movie and when announcing that she was going to grasp an object, she looked straight into the camera. When she moved towards the table and raised her hands to grasp the object, she did not look towards either object but down at her hands. She only looked at an object during the final phase of the grasping action and when expressing whether she liked it or not. The model always grasped the positively cued object. The side of the table to which the model looked first, the color the model preferred, and whether she grasped an object on the left or the right was balanced across the five stimulus movies. �

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Figure 1. Some key frames from the stimulus movie. In the first part of the movie (A), the model expresses her liking for the one and her disliking for the other object. In the second phase of the stimulus movie (B, first picture), she says that she is going to grasp one of the objects, moves towards the table, and lifts her hands. The model then moves her hands and body towards one of the objects and grasps it (B, second and third picture).

Measures. The goal of the looking behavior analysis was to determine whether toddlers showed anticipatory looks to one of the objects and thus expressed an expectation about which object the model was going to grasp. By completing an observed European Journal of Developmental Science [EJDS]. 2009, Vol. 3, No. 4, 368–388 © Vandenhoeck & Ruprecht GmbH & Co. KG, Göttingen 2010, ISSN 1863-3811


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action with their gaze infants reveal information about the expectations they have about an action. Visual anticipations have been used in a number of studies (see e.g., Falck-Ytter et al., 2006; Gredebäck, Stasiewicz, Falck-Ytter, Rosander, & von Hofsten, 2009; Hunnius & Bekkering, in press) and are considered an important addition to the habituation-based looking measures that are traditionally used in infancy research. Compared to habituation-based looking measures the anticipatory looking paradigm has the advantage that it does not require a habituation or learning phase and that it directly assesses the infant’s expectations about observed actions and events (cf. Hunnius & Bekkering, in press). For the looking behavior analysis, areas of interest were defined around the objects to the left and to the right of the model for each movie. These areas of interest were squareshaped and had the same size and position for all objects and all stimulus movies. Furthermore, the stimulus movies were divided into different phases: During the first phase the model expressed her liking and disliking of the objects. The second phase of the stimulus movie showed how she announced to grasp one of the objects, moved towards the table, and lifted her hands. This phase, which featured the beginning of the grasping action, was ambiguous in the sense that it could not be predicted from the movements which object the model was going to grasp. The third phase of the stimulus movie started when the grasping movements became non-ambiguous, as the model moved her hands and body towards one of the objects and then grasped it. To determine whether toddlers anticipated the course of the grasping action with their eye movements, their looking to the two objects was registered throughout the stimulus movie. It was then calculated at which object they looked longer during the second phase, which was the ambiguous grasping phase. For the correlational analyses (see below), the continuous difference in looking time to the “liked” versus the “disliked” object (for the first trial and averaged over all trials) was used. Cooperation Task

After the individual assessments, the toddlers were brought together for a dyadic play session, during which the cooperation task was administered. The computer task and the cooperation task were carried out in two different rooms; the cooperation task was run after both peers had completed the computer task. Play room setup and procedure. After completing the computer task, two experimenters guided the children and their parents to a play room. Parents were asked to take a seat at a table and fill out a form with some background questions or read a magazine. They were asked to reduce their interaction with their child to a minimum. Then, the two toddlers were given the possibility to play together with some toys available in the room. After 10 minutes of free play, during which the two children had the opportunity to get acquainted, the experimenters put away the toys and introduced the cooperation task. It was the goal of this cooperation task to insert a ball into a tube so that it would slide through it and reappear at the bottom end. Before the toddlers were given the tube European Journal of Developmental Science [EJDS]. 2009, Vol. 3, No. 4, 368–388 © Vandenhoeck & Ruprecht GmbH & Co. KG, Göttingen 2010, ISSN 1863-3811

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and ball to play together, the experimenters demonstrated how one person had to hold the tube at its top end and open the lid whereas the other one had to insert the ball. The experimenters demonstrated the task once and then invited the children to insert the ball in the tube together with one of them, before they left the scene saying “And now it is your turn to try!” Then, the peers were given five minutes to play together with the tube and ball. Their interaction was videotaped using two cameras positioned in two corners of the room. Material. Material for this task consisted of a 110 cm colored plastic tube and a table tennis ball. The bottom end of the tube was curved and its top end was closed with a lid that could be opened (see Figure 2). The ball had to be inserted into the tube at the top end so that it would slide through it. Piloting with different versions of this task we had learned that toddlers liked the game of inserting the ball in the tube and watching it reappear at the other end. For the cooperation task the lid was added; it was kept closed by a spring but could easily be opened. In this way, the game could only be played collaboratively, as at the same time the lid had to be opened, the tube had to be held and the ball had to be inserted. The task now also consisted of two sub-tasks, which also differed to some extent in how appealing they were for the toddlers: Whereas one toddler had to hold the tube and open the lid, the other one got to insert the ball.

Figure 2. The colored plastic tube and the table tennis ball which were used in the cooperation task.

Behavioral interaction measures. Toddlers’ interaction behaviors during the cooperation task were coded. A distinction was made between prosocial and affiliative versus antagonistic behaviors during cooperation (cf. Hawley, 2002; Holmes-Lonergan, 2003; Strayer & Trudel, 1984). Examples of affiliative behaviors are communicating, approaching the peer with the ball or tube, and demonstrating to the peer what needed to be done. Antagonistic behaviors included, for example, protesting, taking away the ball or tube from the peer, undermining the actions of the peer, or open aggression. Table 1 lists all coding categories in detail. A new incidence of the same behavioral category was coded if the toddler had stopped the behavior before showing it again, if the toddler had displayed a different behavior in between, or if the other peer had shown a reaction to the toddler’s behavior before he displayed it again. European Journal of Developmental Science [EJDS]. 2009, Vol. 3, No. 4, 368–388 © Vandenhoeck & Ruprecht GmbH & Co. KG, Göttingen 2010, ISSN 1863-3811


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Performance measures. Performance in the cooperation task was measured by numbers of collaborative attempts, successes, and failures. For each individual child it was coded how often they inserted or attempted but did not manage to insert the ball into the tube, while their peer was holding the tube (see Table 1 for a detailed description of the performance measures). Only inserting actions and attempts were coded during which both toddlers were cooperating. Successes and failed attempts were added up which amounted to the number of trials. Table 1. Coding Schema for the Cooperation Task. Affiliative cooperation behaviors: Approach Communication Guiding Handing over Sharing Helping Waiting

Moves with the ball or tube towards the peer who has the other object Indicates in a calm way that he/she wants an object (verbally and/or by pointing) Demonstrates or explains to the peer what needs to be done Leaves an object to the peer Has both objects and allocates one of the objects to the peer Helps the peer, as he/she tries to carry out the task Waits and watches while the peer puts the ball in the tube

Antagonistic cooperation behaviors: Taking away Competing Claiming Protesting Undermining Aggression

Snatches away the ball and/or tube from the peer or aims to do so Races against the peer to get the ball and/or the tube Refuses to share an object (e.g., by turning or walking away from the peer or by pushing the peer away) Protests as a reaction to peer’s behavior (e.g., verbally, crying, possibly towards the parent) Thwarts the action of the peer (e.g., by turning the tube away when the peer tries to insert the ball or by not inserting the ball in the tube which is held by the peer) Aggressive acts towards the peer (e.g., yelling, hitting, kicking, throwing with objects)

Task performance: (only inserting actions and attempts during which both infants are cooperating) Success Failed attempt Attempt Off camera

The child inserts the ball into the tube which is held by the peer, and the ball reappears from the other end of the tube within 3 seconds The child does not manage to insert the ball in the tube (e.g., as the ball falls on the ground or the hatch is closed) or the ball does not reappear at the other end of the tube within 3 seconds (e.g., as the tube is lying on the ground) All successes and failed attempts The child is out of view of the cameras.

For the statistical analyses, relative frequencies of the different behaviors and the performance variables were calculated. The number of incidences for each variable was divided by the individual’s total time spent in view of the cameras. This total time in view of the cameras was calculated by subtracting the time spent off camera from the total interaction time (i.e., 300 sec). Observer reliability. The videos were coded by a single trained observer using the Observer software (Noldus, Wageningen, The Netherlands). The recordings of 6 peers were double-coded after an interval of at least a month. Cohen’s κ ranged between .56 and .77 and was on average .69. European Journal of Developmental Science [EJDS]. 2009, Vol. 3, No. 4, 368–388 © Vandenhoeck & Ruprecht GmbH & Co. KG, Göttingen 2010, ISSN 1863-3811

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Results Intention Understanding Task

First, toddlers’ looking behavior during the intention understanding task was analyzed. Toddlers tended to find the stimulus movies interesting: During the first trial, 43 of the 52 toddlers had a valid trial (i.e., were paying attention throughout the trial). For the second trial, this was 46 toddlers, for the third 41, for the fourth 44, and for the fifth 38. As had been expected, toddlers had significantly more trials in which they looked longer to the “liked” than to the “disliked” object during the ambiguous grasping phase (Mliked = 55.7%), t(51)=1.77, p < .05 (one-tailed), and thus anticipated significantly more frequently to the correct action target. This effect was present even when toddlers watched the stimulus movie for the very first time, when 63% of the 43 toddlers who had valid data looked longer to the “liked” object (χ2(1) = 4.12, p < .05). Interactive Behavior and Cooperation Task Performance

During the 5-min cooperation task, affiliative behaviors occurred on average about nine to ten times per child, whereas during the same time period also about five antagonistic behaviors were observed in each child. The most frequent affiliative behaviors were communicating and approaching, whereas sharing and helping occurred infrequently. The most frequent antagonistic behaviors were protesting and claiming, while aggression and competing were observed only occasionally. During the cooperation interaction, each toddler made on average between one and two attempts to collaboratively solve the task (range 0-6). However, they succeeded much less often, as on average there were only .11 successes per minute per toddler. Of the 38 toddlers, 29 (76.3%) did not succeed on the task during the 5 minutes of cooperative play. However, there was a relatively large range in the success rate, and some toddlers managed to insert the ball into the tube up to five times during the 5-min interaction time. An overview over the average frequencies of the different affiliative and antagonistic behaviors and the task performance variables can be found in Table 2. Assessment of Dyadic Dependence

When analyzing data from dyadic interactions, one has to take into account that the data might be dependent within dyads. That is, the interaction partners might have influenced each other’s behavior during their interaction. Prior to the correlational analyses, it was thus assessed whether the behavior of one peer in a dyad was dependent on the other peer’s behavior. To assess the degree of dependence within dyads, the intraclass correlation (ICC; Kashy & Kenny, 2000) was calculated for each behavioral variable (see Table 3). The ICC expresses the degree of dependence in a variable: A European Journal of Developmental Science [EJDS]. 2009, Vol. 3, No. 4, 368–388 © Vandenhoeck & Ruprecht GmbH & Co. KG, Göttingen 2010, ISSN 1863-3811

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positive ICC points toward similarity within dyads, a negative ICC is indicative of negative dependence within dyads, and an ICC close to 0 indicates the absence of dyadic dependence. The analyses revealed only two significant ICCs: Antagonistic cooperative behavior as well as the frequency of successes in the cooperation task were dependent within dyads. The ICC for the antagonistic behaviors was .43 (p < .05), which indicates that if one child in the dyad showed more antagonistic behaviors, the other one tended to be more antagonistic as well. Also for the frequency of successful task solutions the ICC was positive (ICC = .47, p < .05). So, if one child was more likely to succeed on the task, the other child in the dyad was also more likely to insert the ball in the tube. Because these two variables were mutually dependent, they were analyzed with a model that controls for this dependence (mutual influence model, MIM, see below). For the remaining variables, there was no evidence for dyadic dependence. Therefore, these variables were further analyzed as individual data (see Kenny, Mannetti, Pierro, Livi, & Kashy, 2002). Table 2. Interactive Behavior and Cooperation Task Performance. Mean frequency per minute (SD) Affiliative cooperation behaviors Approach Communication Guiding Handing over Sharing Helping Waiting Antagonistic cooperation behaviors Taking away Competing Claiming Protesting Undermining Aggression Performance measures Successes Failed attempts Attempts

1.94 (1.72) .49 (.54) .92 (.83) .11 (.22) .24 (.51) .02 (.08) .04 (.11) .11 (.35) 1.11 (1.06) .24 (.36) .05 (.11) .37 (.40) .31 (.50) .09 (.18) .04 (.12) .11 (.24) .17 (.26) .29 (.35)

Relation Between Intention Understanding and Cooperation Behavior

Analyses at the individual level. The zero-order correlations between the two measures of intention understanding (difference in looking time to the “liked” versus the “disliked” object for the first trial and averaged over all trials) and the toddlers’ inEuropean Journal of Developmental Science [EJDS]. 2009, Vol. 3, No. 4, 368–388 © Vandenhoeck & Ruprecht GmbH & Co. KG, Göttingen 2010, ISSN 1863-3811

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teraction behaviors are given in Table 4. T tests were carried out to examine whether the correlation coefficients were significantly different from zero. Both intention understanding measures were positively correlated with affiliative cooperation behaviors (rs = .35 and .40, respectively), whereas they were negatively correlated with antagonistic cooperation behaviors (rs = -.41 and -.29, respectively). Of the affiliative cooperation behaviors, handing over (rs = .39 and .50, respectively), approach (r = .33), helping (r = .28), and waiting (r = .51) were shown to correlate positively with intention understanding. Marginally significant positive correlations were found for communicating (r = .26) and guiding (r = .25). The antagonistic cooperation behaviors claiming (r = -.36 and r = -.27) and protesting (r = -.42) were negatively related to the measures of intention understanding. Table 3. Intraclass Correlations for the Cooperation Behavior Variables. Intraclass correlation Affiliative cooperation behaviors Approach Communication Guiding Handing over Sharing Helping Waiting Antagonistic cooperation behaviors Taking away Competing Claiming Protesting Undermining Aggression Performance measures Successes Failed attempts Attempts

.29 .04 .30 -.07 .14 .00 -.12 -.04 .43* -.08 .15 -.04 .22 .05 -.11 .47* -.19 .21

* p < .05

Analyses at the dyadic level. The relation between intention understanding and antagonistic cooperation behavior was analyzed using the mutual influence model for dyadic data (MIM; Kenny, 1996; Woody & Sadler, 2005), as the examination of dyadic dependence had shown that toddlers’ display of antagonistic cooperation behavior was similar within dyads. Using the MIM, we examined two types of effect, the actor effect of the child’s intention understanding on his or her own antagonistic cooperation behavior and the partner effect of the peer’s antagonistic behavior on European Journal of Developmental Science [EJDS]. 2009, Vol. 3, No. 4, 368–388 © Vandenhoeck & Ruprecht GmbH & Co. KG, Göttingen 2010, ISSN 1863-3811

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the child’s behavior (see Figure 3). The estimation of the MIM was conducted using structural equation modeling (AMOS 7.0). Separate analyses were conducted for the two variables of intention understanding. Only the model with the difference in look duration averaged over all trials as predictor yielded an acceptable model fit. Model fit was excellent (χ2(6) = 1.21, p = .98, CFI = 1, RMSEA = 0). The actor effect of -.30 was marginally significant (p = .09), whereas the partner effect of .44 did not yield statistical significance (p = .16). � ��

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Figure 3. The mutual influence model which predicts toddlers’ antagonistic cooperation behavior on the basis of their intention understanding. U and V represent the disturbances (unexplained variances) of the dependent variables.

Relation between Intention Understanding and Cooperation Performance

The two measures of intention understanding were not significantly correlated with any of the cooperation performance measures (all ps > .10; see Table 4). The MIM with the frequency of successes as dependent measure did not yield an acceptable model fit and was not further pursued. Discussion

This study examined whether young children’s social understanding is linked to their behavior during peer cooperation. It was expected that toddlers’ ability to understand others’ intentions would be related to harmonious peer interactions and good coopEuropean Journal of Developmental Science [EJDS]. 2009, Vol. 3, No. 4, 368–388 © Vandenhoeck & Ruprecht GmbH & Co. KG, Göttingen 2010, ISSN 1863-3811

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eration performance. Children carried out two tasks, a computerized intention understanding task and a cooperation task together with an unfamiliar peer. In the intention understanding task it was examined whether the toddler predicted a model’s actions on the basis of her perceptual-emotional displays (cf. Barna & Legerstee, 2005; Phillips et al., 2002). In the subsequent cooperation task, toddlers were coupled with an unfamiliar peer to play a cooperative game. Their cooperation behavior was coded in terms of interaction behaviors and task performance. Toddlers readily engaged in the suggested cooperative game; however, they succeeded much less frequently. Intention understanding was positively correlated with affiliative behavior, and negatively with antagonistic behaviors during the cooperation task. Measures of cooperation task performance, however, were not related to toddlers’ intention understanding. Toddlers’ capability to understand others’ intentions was thus closely associated with how they interacted with a peer, but not with how successful they were in the cooperation task. Table 4. Pearson Correlations Between the Measures of Intention Understanding and Peer Cooperation. Difference in look duration to correct versus incorrect object Affiliative cooperation behaviors Approach Communication Guiding Handing over Sharing Helping Waiting Antagonistic cooperation behaviors Taking away Competing Claiming Protesting Undermining Aggression Performance measures Successes Failed attempts Trials t

.35* .16 .26t .00 .39** .03 .08 .26t -.41** -.10 .06 -.36* -.42** -.17 -.18 .15 -.12 .02

Difference in look duration to correct versus incorrect object (First Trial) .40** .33* -.01 .25 t .50** .01 .28* .51** -.29* -.07 -.14 -.27 t -.21 -.20 -.18 -.10 .03 -.05

p < .10; * p < .05; ** p < .01, one-sided.

With regard to children’s behavior in the cooperation task, it is remarkable that overall, toddlers succeeded only infrequently to solve the cooperation task together. During the five minutes they played together with the tube and the ball, each dyad European Journal of Developmental Science [EJDS]. 2009, Vol. 3, No. 4, 368–388 © Vandenhoeck & Ruprecht GmbH & Co. KG, Göttingen 2010, ISSN 1863-3811


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managed on average only once to cooperatively insert the ball into the tube. The majority of dyads, however, did not achieve the goal of the task (cf. Brownell et al., 2006). The cooperation task in this study thus formed a challenge for our sample of 19-month-olds. This is consistent with earlier studies indicating that efficient and smooth cooperation between peers emerges only around two years of age (Brownell & Carriger, 1990; Brownell et al., 2006; Eckerman, Davis, & Didow, 1989; Friedlmeier, 2009). By 18 months of age cooperative acts during peer interaction appear to occur only infrequently and accidentally (Brownell & Carriger, 1990), but towards the end of the second year of life, a significant increase in spontaneous cooperative acts has been observed (Eckerman et al., 1989), and around 24 to 30 months of age children begin to reliably cooperate with each other (Brownell & Carriger, 1990). How successful young children are in performing cooperative acts also depends on the nature of cooperation required in the task (Brownell et al., 2006). Whereas cooperation that involves imitative actions to be performed in parallel can be observed relatively early in life (Mueller & Brenner, 1977), cooperation tasks that require complementary actions and temporal coordination emerge only during the third year of life (Ashley & Tomasello, 1998; Meyer et al., 2009). To successfully carry out the task of our study, the 19-month-old children had to perform complementary actions on different objects and coordinate their actions rather precisely in time and space. This might have contributed to their difficulties with the task and the relatively low frequency of successful cooperation task solutions. Previous research has demonstrated that during peer interactions conflicts among toddlers tend to occur frequently (Hay & Ross, 1982) and usually take place when two peers try to get access to the same resource, object, or activity (Bronson, 1981; Fagot & Hagan, 1985; Ross & Goldman, 1977). The interaction task in our study was centered around two portable objects that had to be divided and used in a joint activity, and there were no alternative toys available. As a consequence, behaviors like claiming both objects or protesting in reaction to the peer’s behavior were the most frequent antagonistic behaviors, whereas handing over an object to the peer or helping each other occurred rarely. This is consistent with earlier findings on object conflicts and sharing in toddlers, which show that toddlers have a relatively self-biased concept of possession (Brownell & Brown, 1985) and that spontaneous sharing of toys or food is uncommon throughout early childhood (Brownell, Svetlova, & Nichols, 2009; Grusec, 1991; Hay et al., 1999; Viernickel, 2009). Overall, however, the toddlers in our study showed more affiliative than antagonistic behaviors when interacting with each other, and physical aggression like beating or kicking the peer was hardly ever observed (cf. Brownlee & Bakeman, 1981; Fagot & Hagan, 1985). During the course of an interaction between individuals, reciprocity effects occur frequently, as people tend to influence each other in their behaviors. The analyses of dyadic dependency for the interaction behaviors revealed that toddlers influenced each other only in their antagonistic behaviors. If one peer exhibited more antagonistic behaviors, the other one was more likely to show antagonistic interaction behaviors as well. This is European Journal of Developmental Science [EJDS]. 2009, Vol. 3, No. 4, 368–388 © Vandenhoeck & Ruprecht GmbH & Co. KG, Göttingen 2010, ISSN 1863-3811

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in accordance with previous findings that aggressive and antagonistic behaviors among young and older children are often reciprocal (e.g., Dishion, Andrews, & Crosby, 1995; Price & Dodge, 1989; Ross, Conant, Cheyne, & Alevizos, 1992). Interestingly, no such effect was found for affiliative behaviors. A more affiliative interaction style of one peer was not associated with more frequent affiliative behaviors from the partner which is consistent with findings on the socialization of prosocial behavior. Here, it has been shown that preschoolers’ reactions to their peers’ prosocial acts are not necessarily positive (Eisenberg, Cameron, Tryon, & Dodez, 1981; but see Fujisawa, Kutsukake, & Hasegawa, 2008). On the other hand, toddlers did appear to influence each other in an aspect of constructive task behavior: If one peer was more successful on the task and managed to let the ball roll through the tube more frequently, the other peer was more likely to be successful as well and insert the ball in the tube more often. It thus appears that, to a certain extent, peers learned from each other and improved each other’s performance. Thus, although earlier studies have shown that toddlers have difficulties adjusting their behavior to the behavior of their peers during a cooperation task (cf. Brownell & Carriger, 1990; Brownell et al., 2006), the current study shows that dyadic influence in constructive task behavior can be observed. Toddlers’ intention understanding was examined with a computerized task. The 19month-old infants in our study performed well on this task, as they visually anticipated that the model would grasp the object she liked significantly more often than the object she disliked. To accurately predict the model’s grasping toddlers needed a number of skills: Anticipating correctly required the ability to follow the other person’s gaze, to interpret basic emotional expressions, to relate the observed gaze and emotion displays to an object and subsequently to an action intention, and to predict the course of the action on the basis of prior information (cf. Wellman & Phillips, 2001). The current findings with 19-month-old infants replicate earlier studies which used comparable stimuli with 9- to 12-month-old infants (Barna & Legerstee, 2005; Phillips et al., 2002). The present results also extend these previous findings, as it could be shown that toddlers used the knowledge they acquired from another person’s expressions of liking and disliking to predict her subsequent actions. This direct link between toddlers’ knowledge of another person’s preferences and the expectations they form about her actions has not been shown to date. Interestingly, the 19-month-olds in our study not only showed more frequent anticipations to the correct object averaged over the five experimental trials, but visually predicted which object would be grasped when observing the model’s actions for the first time. Thus, the toddlers were not only able to learn that the model tended to grasp objects she liked, but they knew from the very beginning that a person would grasp an object she likes rather than an object she dislikes. Most importantly, the current study demonstrates close correlations between toddlers’ intention understanding and their peer interaction behavior during cooperation. More frequent affiliative behaviors in the cooperation task were associated with a better performance on the intention understanding task, whereas antagonistic behaviors were correlated with less correct intention prediction. It is remarkable that practically European Journal of Developmental Science [EJDS]. 2009, Vol. 3, No. 4, 368–388 © Vandenhoeck & Ruprecht GmbH & Co. KG, Göttingen 2010, ISSN 1863-3811


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all affiliative behaviors showed a positive correlation with one of the two variables of intention understanding. Toddlers who predicted the model’s grasping action more correctly approached and helped the partner peer, handed over objects, and waited for the peer’s action more often. They also tended to communicate or demonstrate more often how to solve the task together. In contrast, antagonistic behaviors were negatively associated with children’s intention understanding: Toddlers who performed worse in the intention understanding task were more likely to refuse to share an object and to protest during the cooperation task. To date, links between social understanding and peer interaction among young children have been studied only seldom. However, a few recent studies have provided evidence that toddlers who perform better on tasks reflecting emotion understanding, joint attention, and language abilities, also show more partner-sensitive, affiliative behaviors and better cooperation (Brownell et al., 2006; Ensor & Hughes, 2005; Smiley, 2001). Brownell and colleagues (2006), for example, have shown that coordinated activity during cooperation with a peer is associated with attention sharing with an adult and with language abilities. In slightly older children, the ability to label emotional expressions correctly has been shown to be related to positive behaviors during interaction with a peer (such as joining the peer’s play; Ensor & Hughes, 2005). The results of the current study fit these findings well, as they also indicate links between social-cognitive competencies and peer interaction already in early childhood. Different mechanisms might underlie the association between young children’s intention understanding and cooperation. One possibility is that infants’ social understanding influences how they interact and cooperate. In this view, children’s affiliative and cooperative behavior is grounded to a large extent in their social understanding and social-cognitive abilities (see, e.g., Denham, 1986; Ensor & Hughes, 2005; cf. Brownell et al., 2006; Brownell & Hazen, 1999). Consistent with this interpretation, one might argue that the children in our study who displayed more affiliative behaviors and who behaved more “in tune” with their peer did so because they understood the peer’s intentions better and were better able to predict their next actions. However, another possibility is that children’s intention understanding and their cooperative behavior are both determined by an underlying third factor. Young children differ in their general interest in others, motivation to engage in social interaction, degree of behavioral inhibition, and temperamental style (see Brownell & Hazen, 1999; Kochanska & Radke-Yarrow, 1992; Rothbart & Bates, 1998). These differences might influence children’s behavior with a peer and – as they create different experiences with the social world – their social-cognitive development. According to this view, one could suggest that the toddlers in our study who tended to show non-social behaviors (i.e., refused to share an object, protested when the peer approached) might have done so as a consequence of their lower interest in social interaction and social stimuli in general. This general lack of social motivation might also have caused a less optimal performance on the computer task, where children might have been less able or less motivated to visually anticipate the model’s actions. The current study cannot conclusively determine European Journal of Developmental Science [EJDS]. 2009, Vol. 3, No. 4, 368–388 © Vandenhoeck & Ruprecht GmbH & Co. KG, Göttingen 2010, ISSN 1863-3811

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which of these two interpretations is more correct. More research is needed to further disentangle this intertwining of early social and social-cognitive development. Interestingly, our study did not demonstrate an association between toddlers’ intention understanding and successful solutions to the cooperation task. Previous research suggests an association between toddlers’ social-cognitive competencies such as attention sharing and language about self and others and their cooperative performance (Brownell et al., 2006). However, as mentioned above, the cooperation task of the present study presented the 19-month-old infants with a difficult challenge. They had to coordinate complementary actions precisely in time and space to insert the ball in the tube. As a result, three out of four dyads did not succeed even once, and luck or persistence rather than social-cognitive skill may have accounted for most of the variance in task performance. Thus, although differences in social understanding were associated with differences in cooperative behavior, they did not predict how successful the children were in the end. How young children behave in interactions with peers is of great importance for their social development in general. Research on the early origins of peer social skills and peer acceptance has revealed consistent individual differences in how young children interact with peers as early as the first years of life (Howes, 1980). These individual differences in peer competence appear to be relatively stable throughout childhood. Moreover, toddlers’ skilled social play predicts later competence during peer interactions at preschool- and school-age (Howes & Phillipsen, 1998). The evidence for stable individual differences in peer competence from early childhood on emphasizes the importance of exploring the factors that influence young children’s interactive and cooperative behavior with peers when it is still emerging. The associations between 19-month-old infants’ social understanding and their affiliative and antagonistic behaviors during cooperation found in this study thus add to our understanding of the earliest origins of peer social skills.

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European Journal of Developmental Science [EJDS]. 2009, Vol. 3, No. 4, 368–388 © Vandenhoeck & Ruprecht GmbH & Co. KG, Göttingen 2010, ISSN 1863-3811