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Journal of Cognition and Development
Publicat ion det ails, including inst ruct ions f or aut hors and subscript ion inf ormat ion:ht t p: / / www. t andf online. com/ loi/ hj cd20
Concurrent Relations Between
Perspective-Taking Skills, Desire
Understanding, and Internal-State
Vocabulary
Sabrina S. Chiarella a , Susanne Krist en b , Diane Poulin-Dubois a & Beat e Sodian b
a
Concordia Universit y , Canada
b
Ludwig Maximilians Universit y of Munich , Germany
Accept ed aut hor version post ed online: 28 Jun 2012. Published online: 22 Aug 2013.
To cite this article: Sabrina S. Chiarella , Susanne Krist en , Diane Poulin-Dubois & Beat e Sodian (2013) Concurrent Relat ions Bet ween Perspect ive-Taking Skills, Desire Underst anding, and Int ernal-St at e Vocabulary, Journal of Cognit ion and Development , 14: 3, 480-498, DOI:
10. 1080/ 15248372. 2012. 689390
To link to this article: ht t p: / / dx. doi. org/ 10. 1080/ 15248372. 2012. 689390
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ARTICLE
Concurrent Relations Between Perspective-Taking Skills,
Desire Understanding, and Internal-State Vocabulary
Sabrina S. Chiarella
Concordia University, CanadaSusanne Kristen
Ludwig Maximilians University of Munich, Germany
Diane Poulin-Dubois
Concordia University, Canada
Beate Sodian
Ludwig Maximilians University of Munich, Germany
Recent studies suggest that there appears to be a similar developmental sequence in the understanding of mental states in both internal-state language and in standard theory-of-mind tasks. These findings suggest possible developmental relations between children’s ability to talk and think about the mind. Two experiments investigated the concurrent relations between internal-state vocabulary and theory-of-mind abilities in 30-month-old toddlers. In Experiment 1, children’s internal-state language vocabulary was significantly and specifically related to their concurrent understanding of others’ visual and emotional perspectives and was less strongly related to desire understanding. Experiment 2 replicated and extended these findings by examining the link between internal-state vocabulary and visual perspective-taking and comprehension of own versus other’s desire, controlling for general ver-bal skills. Children with a more developed internal-state vocabulary performed better on perspective-taking tasks. These findings suggest that labeling and reasoning about mental states are related abilities at the early stages of theory-of-mind development.
The ability to talk about the mind, labeled mental- or internal-state language, begins to emerge late in the 2nd year of life (Bretherton, McNew, & Beeghly-Smith, 1981). Consequently, the ability for children to reason about their own and others’ thoughts, feelings, and emotions
Correspondence should be sent to Sabrina S. Chiarella, Center for Research in Human Development, Department of Psychology, Concordia University, 7141 Sherbrooke St. West, PY-170, Montreal, QB, Canada H4B 1R6. E-mail: [email protected]
DOI: 10.1080/15248372.2012.689390
becomes observable and explicit. In the first documented study examining internal-state language in toddlers, Bretherton and Beeghly (1982) reported that children’s vocabulary about the mind could be grouped into six word categories: perception, physiological, volition, cognition, moral judgment, and obligation. The researchers also reported a developmental progression in the acquisition of these categories. Specifically, at 28 months, children produced perceptual and volition words the most relative to the other word categories, followed by physiological, emotion-al, and moral words, with the least produced being cognition words (Bretherton et al.). Similar results were found by Poulin-Dubois and her colleagues, in both English- and French-speaking populations of 32-month-old infants (Poulin-Dubois, Chiarella, & Polonia, 2009). The late emergence of cognitive words in these samples was also confirmed in speech samples col-lected by Shatz and her colleagues, who noted that relative to other mental-state terms, cogni-tive words were most utilized by children in the 3rd year of life and were used for pragmatic conversational functions (Shatz, Wellman, & Silber, 1983). Moreover, a longitudinal study by Bartsch and Wellman (1995) using data drawn from the CHILDES database examining internal-state words in children between the ages of 18 months and 5 years revealed that their internal-state utterances could be classified into two broad categories: thought and belief terms (e.g.,think, know) and desire terms (e.g.,want, wish). The findings revealed that desire terms were produced earlier than thought and belief terms. In addition, thought and belief terms only began to match the frequencies of the desire terms at 5 years of age (Bartsch & Wellman). The acquisition of desire terms before other internal-state terms has also been found in the speech of children who speak languages other than English (Ferres, 2003; Pascual, Aguado, Sotillo, & Masdeu, 2008; Tardif & Wellman, 2000). In sum, studies based on both maternal reports and speech samples collected in naturalistic settings show a similar developmental pattern of the mental lexicon. Given this parallel sequence, one would expect that maternal reports of internal-state language provide a valid measure of children’s internal-state language in the same way that maternal reports of general language (i.e., MacArthur Communicative Devel-opment Inventories (MCDI)) are a widely accepted index of children’s general language skills (cf. Thal & Bates, 1988).
With respect to these findings, it can be assumed that children’s ability to verbalize their own and others’ mental states reflects some understanding that others may have different beliefs, per-ceptions, desires, and emotions than one’s own. This understanding is commonly referred to as having a theory-of-mind (ToM). There is a general consensus that children’s explicit understand-ing of the mind develops in the early childhood period, specifically before the age of 4 or 5 years (Wellman, 2010). In addition, research has shown the existence of a developmental progression as to exactlywhich internal states develop first (Wellman & Liu, 2004). For instance, a two-step sequence has been proposed, with children’s understanding of desires preceding their understand-ing of beliefs (Wellman & Liu). Specifically, by 3 years of age, children begin to understand that others can have different desires than their own, followed by an understanding that others may hold diverse beliefs by 4 years of age, and that they may hold false beliefs by 5 years of age (Lillard & Flavell, 1992; Wellman & Liu). Although cultural differences may exist as to the exact ages that children begin to develop an understanding of different internal states (e.g., desires vs. beliefs), the sequence of acquisition of different ToM abilities seems to remain constant across cultures (Wellman; Wellman, Fang, Liu, Zhu, & Liu, 2006; Wellman & Liu). Thus, there appears to be a similar developmental sequence in the understanding of mental states in both internal-state language and in children’s abilities to solve ToM tasks.
In addition to the sequence of acquisition of ToM constructs, the coherence among success rates on various ToM tasks is an important issue that has received less attention from researchers, particularly early in development. Previous research has shown that performance across belief tasks tends to be consistent in preschoolers and school-age children (e.g., Gopnik & Astington, 1988; Moore & Furrow, 1991). Given that some implicit form of understanding of mental states is now well documented during the first 3 years of life, it has recently been possible to address inter-task coherence during that developmental period (Poulin-Dubois, Brooker, & Chow, 2009; Sodian, 2011). The few studies available on toddlers have revealed weak or modest relations between tasks tapping into the understanding of different mental states. Carlson, Mandell, and Williams (2004) found that among four ToM tasks administered at 2 years of age, only the under-standing of discrepant desires and intentions remained associated after controlling for age, sex, and verbal ability. When the children were 3 years of age, inter-task correlations remained weak, with only pretend-reality and appearance-reality tasks remaining strongly correlated after controlling for the same variables (Carlson et al.). Similarly, Hughes and Ensor (2007) found that inter-ToM correlations among 2-, 3-, and 4-year-olds disappeared when controlling for age and verbal ability. To date, only one study has been conducted with infants, and it has shown that performance on intention and false-belief tasks is unrelated at 18 months of age (Yott & Poulin-Dubois, 2012).
Interestingly, in contrast to behavioral ToM measures, talkingabout the mind seems to be a better predictor of children’s later behavioral ToM skills. In one of the first studies examining children’s usage of internal-state language, J. Dunn and Brown (1991) found that children who spoke more about their feelings with siblings at 33 months showed a better ToM perfor-mance on false-belief and affective perspective-taking tasks at 40 months. In a longitudinal study by Hughes and Dunn (1998), 4-year-old children who engaged in more internal-state talk with friends also performed better on a concurrent false-belief task, and did so again 13 months later, but not on the understanding of emotion. Nielsen and Dissanayake (2000) examined internal-state word utterances in 3-and 4-year-old preschoolers during play with a parent and found a significant correlation with concurrent false-belief and symbolic play performances.
In contrast, nonsignificant findings have emerged for older children’s (6 to 12 years old) ToM performance (including false-belief understanding, belief–desire reasoning, understanding of pretense and deception) when their usage of internal-state terms was assessed during noninterac-tional tasks (i.e., narrative of a picture story; Charman & Shmueli-Goetz, 1998; Harris, Johnson, Hutton, Andrews, & Cooke, 1989; Meins, Fernyhough, Johnson, & Lidstone, 2006; Tager-Flusberg & Sullivan, 1995).
Importantly, two issues must be raised with respect to the aforementioned findings. First, it may be that no consistent link has been found between ToM skills and internal-state language because monitoring children’s internal-state word usage may not necessarily reflect the richness of their vocabulary in noninteractional contexts. That is, even if children’s usage of internal-state words may be high, they might use a limited repertoire of words in narrations, underestimating the total number of internal-state words that they are able to express. Second, the significant findings between mental-state usage, by way of word frequencies and conversational turns (which include repetition of the same words) and ToM (e.g., J. Dunn & Brown, 1991; Hughes & Dunn, 1998; Nielsen & Dissanayake, 2000) may overestimate the degree of concordance between ToM and internal-state language skills. Specifically, mental-state usage may be overestimated in these conversational contexts, as it does not capture thebreadthof words in a child’s mental lexicon. Thus, monitoring children’svocabulary about the mind, rather than usage, would provide a more reliable way of
assessing the range of internal-state words in children’s lexicon. Furthermore, as with usage, monitoring children’sexpressivevocabulary (rather than receptive vocabulary) would allow for a better assessment of their ability to explicitly reflect on their own internal states. That is, although children mayunderstanda large range of mental terms,usingthese words provides a more reliable and conservative index that children are referring to their own internal states.
Interestingly, there is a paucity of research examining the relation between ToM skills and mental-state vocabulary terms in children. Repacholi and Gopnik (1997) explored the associa-tions between 14- and 18-month-old infants’ understanding of desires and their concurrent internal-state word vocabulary but found no significant findings. In contrast, despite the lack of concurrent associations found between behavioral ToM measures in toddlers, Olineck and Poulin-Dubois (2005) showed that 14- and 18-month-old infants’ ability to differentiate between intentional and accidental actions was predictive of infants’ internal-state vocabulary at 32 months of age. In a second study, with the same cohort of children, internal-state vocabulary at 32 months of age was predictive of a range of ToM skills at 4 years of age, including false-belief and a battery of ToM skills (Olineck & Poulin-Dubois, 2007). Similarly, in slightly older children, Carlson and her colleagues (2004) found that 24-month-olds’ internal-state vocabulary was related to their concurrent understanding of pretense, as well as their later understanding of pretend versus reality and a ToM composite score at 39 months of age.
Taken together, the previous findings suggest that children’s internal-state language may be an early indicator of later ToM abilities, beyond behavioral ToM skills early in infancy. Lacking in the literature is a more comprehensive understanding of how internal-state vocabulary and the understanding of others’ emotions, desires, and perspectives are concurrently associated in late infancy and early toddlerhood. More specifically, only one study to date has examined internal-state vocabulary and concurrent ToM abilities, but the limited significant results may be explained by the absence of age-appropriate ToM tasks (Carlson et al., 2004). Moreover, children in that study were reported to use only 23%of the internal-state words in the checklist, a low
proportion considering that children at this age are increasingly developing their mental lexicon. Importantly, Carlson and her colleagues did not examine children’s vocabulary in each of the six internal-state word categories, despite the fact that children have been reported to use a differential proportion of internal-state word categories at this age (Bartsch & Wellman, 1995; Bretherton & Beeghly, 1982; Poulin-Dubois, Chiarella, et al., 2009).
The main goal of the present study was to examine internal-state vocabulary in young children and its concurrent relation to their understanding of others’ internal states. Given that previous studies have found strong relations between concurrent internal-state usage and ToM tasks and that one study (Carlson et al., 2004) found some relations among ToM and internal vocabulary, it was hypothesized that there would be a link between internal-state vocabulary and early ToM skills in 30-month-old children. More specifically, it was predicted that a strong relation between visual perspective-taking skills and internal-state language would be observed. Simulation theory argues that both ToM and visual perspective-taking involve a process of setting aside one’s current point of view and putting oneself into the shoes of another person (Langdon & Coltheart, 2001). Harris (1992, 1996) stresses that language facilitates the under-standing of another’s perspective because appropriate conversations require a strict bidirectional interaction between two individuals who recognize and take into account each other’s point of view (cf. K. Farrant & Reese, 2000). Thus, the individual is encouraged to mentally adopt another person’s perspective, and the immediate feedback given in conversation is likely to
improve one’s ability to accurately imagine others’ perceptions. In support of this theory, a study by B. M. Farrant, Fletcher, and Maybery (2006) showed delayed development of Level 2 visual perspective-taking skills in 60-month-olds with specific language impairment.
Relatedly, conversations about internal states in particular may be positively related to perspective-taking skills, even early in development. For instance, Moore (2006) postulated that although young children’s grasp of the semantic meaning of internal-state terms may be questionable, internal-state terms are used to coordinate the multiple perspectives of human agents early in development, thus helping children to recognize when perspectives coincide or diverge. In addition, many of the critical cognitive skills involved in perspective-taking are crucial for children’s development of internal-state language. For instance, mental perspectives and internal-state terms are intangible and thus are difficult to derive from the visual spatial scene (Gleitman, 1990; Hall & Nagy, 1987; Montgomery, 2002). Therefore, strong and specific relations are to be expected between perspective-taking skills and children’s internal-state vocabulary. To date, there is a lack of empirical evidence for early developmental relations between internal-state language skills and Level 1 visual and other mental perspective-taking.
To close the gap in the literature, English-speaking children’s internal-state vocabulary was examined in relation to visual and emotional perspective-taking skills as well as desire understanding in Experiment 1. Given the age of the sample, a Level 1 (Flavell, Everett, Croft, & Flavell, 1981) visual perspective-taking task was used. The specificity of the link between internal-state words and ToM concepts (e.g., the concepts of desire and emotion) was also explored. In Experiment 2, an attempt was made to replicate these findings with a group of German-speaking tod-dlers on a different desire task as well as a visual perspective-taking task. In addition, Experiment 2 included a measure of general language skills to verify the specificity of the link between internal-state vocabulary and visual perspective-taking skills and to further explore the link between internal-state vocabulary and comprehension of own versus another’s desire beyond general language skills.
EXPERIMENT 1
Method
Participants
A total of 59 toddlers participated in this experiment. Five children had to be excluded from the analyses due to parents’ failure to return the Mental Lexicon Questionnaire (n¼4) and due to fus-siness (n¼1). The final sample included 54 toddlers, with 26 females and 28 males, of which 43 were English-speaking and 11 were French-speaking. The children’s mean age was 2;8 years (SD¼2.55 months; range¼2;5–3;2 years). The participants were recruited from birth records pro-vided by a public government health agency or from birth announcements in a local newspaper. They were all from middle- and upper middle-class families living in Eastern Canadian cities.
Procedure
The children and their parents were first taken to a reception room where they were familiar-ized with the two experimenters. Parents were given information about each of the tasks in which
their child would take part and then were asked to sign a consent form and complete a demographic information form. Following this familiarization period, the children were brought into the testing room and seated in a highchair or booster seat. The parent sat behind their child and was asked not to interfere during testing. All of the tasks were counterbalanced and the participants were given $30 for their participation and for the completion of the questionnaire. The children received a stuffed animal and a certificate of merit at the end of the session for their participation.
Mental Lexicon questionnaire. Adapted from Bretherton and Beeghly’s (1982) Internal-State Language Questionnaire, the Mental Lexicon Questionnaire (MLQ) is a parent-report checklist of children’s expressive vocabulary about the mind. The English version of the MLQ included 78 internal-state words separated into six categories: 1) Perception (13 words; e.g.,see, look, hear, taste); 2) Physiology (11 words; e.g.,hungry, tired, thirsty, asleep); 3) Emotion=Affect (28 words; e.g.,happy, nice, mad, OK); 4) Volition=Ability (4 words; e.g.,
want, can, need, have to); 5) Cognition (12 words; e.g.,know, understand, think, pretend); and 6) Moral Judgment=Obligation (10 words; e.g.,good, can, bad, let). Adapted from the English questionnaire, the French version contained 75 internal-state words divided into the same six aforementioned categories: Perception (12 words), Physiology (10 words), Emotion=Affect (28 words), Volition=Ability (5 words), Cognition (11 words), and Moral Judgment=Obligation (9 words; Poulin-Dubois, Chiarella, et al., 2009). There were no translation equivalents for three of the English words (i.e., warm, may, and have to). The discrepancy in the number of items across the questionnaires was addressed in the current analyses by using the proportion of words infants used in that category relative to the total number of words included in the category; this method allowed for the MLQ scores of the language groups to be collapsed (see Poulin-Dubois et al., 2009, for a comparison of these two checklists).
Emotional perspective-taking: Puppet story task. To assess children’s ability to reason about others’ emotions, a procedure modified from Wellman and Woolley’s (1990) puppet story task was utilized. Children were first shown a character and told that he or she was happy, and then they were presented with a cardboard cut-out face with a happy expression. They were then given the opportunity to place the happy face on the character and were asked to identify how the character was feeling. The same trial was done with a sad expression, in a counterbalanced order. Once the children correctly recognized both the happy and sad faces (100%of children in this
sample), they were administered the six test-trial stories. During each test trial, the experimenter would announce what the character was looking for and would point to the place where it might be. Then, she would playfully walk the character to the scene, look behind the picture, and then grab the object from the box behind the scene. In two of the trials, the character found what he or she was looking for, and in four trials he or she did not. In all the test trials, the experimenter maintained a neutral tone and affect and then asked the child if the character was feeling happy or sad. When the child answered, the experimenter placed the character in a Styrofoam square, held up the happy and sad faces on each side of the character, and asked the child to place the emotional expression on the character. If the child did not immediately answer, he or she was shown the happy- and sad-face cut-outs and was queried again. All the children responded to either the verbal prompt or chose a cut-out face. Children who verbally responded were also given the face cut-outs to place on each character. All the children who provided a verbal response chose the equivalent face cut-out. The order of the queried emotion was counterbalanced for each
story (e.g., ‘‘Is Samhappy, or is hesad?’’; ‘‘Is Betsysad, or is shehappy?’’). The children’s answers were given a score of 1 if they identified the correct emotion of the character. The maximum total possible score was 6.
Desire: Broccoli task. Adapted from a task used by Repacholi and Gopnik (1997), children’s abilities to infer desire from emotional expressions were assessed. The test trials con-sisted of four food items, presented in two pairs (appealing=unappealing items) in counterba-lanced order. To ensure that there would be food items that the majority of the children liked, Pepperidge Farm Goldfish Crackers, Arrowhead Cookies, Fruit Loops cereal, and raisins were counterbalanced and presented with typically unappealing food to children: broccoli, lettuce, cauliflower, and celery. The appealing–unappealing paired food items were presented one pair at a time in two separate bowls. The experimenter began by saying, ‘‘Here’s a snack for you! You can eat it. You can have whichever one you’d like,’’ and then gave the child 35 seconds to try the food items and to determine the child’s food preference. After the 35 seconds, the exper-imenter said, ‘‘OK! Now it’smy turn!’’ and tasted the food item. When holding the child’s preferred food item (e.g., crackers), the experimenter said, ‘‘Ew! Crackers! Ew! I tasted crackers! Ew!’’ and displayed an expression of disgust. When holding the child’s nonpreferred food item (e.g., broccoli), the experimenter said, ‘‘Mm! Broccoli! Mm! I tasted Broccoli! Mm!’’ as she displayed a happy face. Each demonstration trial lasted approximately 10 seconds, and the display of disgust and happy faces were counterbalanced (i.e., the experimenter always began by tasting the food item on the left, which was the preferred food item on half of the first trials). The bowls were then returned to the child, and the experimenter held out her right hand at equal distance between the two bowls and asked ‘‘Can I have one please?’’, If the child did not respond, the experimenter said, ‘‘I’m hungry. Can I have one please?’’, The child was given a score of 1 if he or she chose the experimenter’s preferred food item. The maximum total possible score was 2.
Visual perspective-taking tasks. Taken from Flavell and colleagues (1981), two tasks were administered to assess the children’s visual perspective-taking abilities. The child was seated in front of the experimenter and was first presented with an 8.5-11-inch board that had a picture
of a cat on one side and a dog on the other. The board was placed on the table so that the child could only see one animal, and the child was then asked, ‘‘What animal is this?’’. If the child responded correctly (which included answers such as ‘‘cat,’’ ‘‘meow meow,’’ or ‘‘kitty’’ for the cat; or ‘‘dog,’’ ‘‘doggy,’’ or ‘‘woof woof’’ for the dog), the experimenter praised the child and repeated the name of the animal. If the child did not answer, the experimenter aided the child by saying, ‘‘What sound does this animal make?’’ and re-asked the name of the animal. If the child still did not respond, the experimenter asked the child if it was a cat (or a dog). All of the children in this sample identified the animals. The experimenter then flipped the card over and asked the child to name the next animal in the same manner as indicated above. After the child identified both animals, the experimenter placed the card upright on the table with the picture of the first animal toward the child and asked, ‘‘Now, what animal canyousee?’’ and then, ‘‘What animal canIsee on my side?’’. The experimenter then turned the card over and asked the same question for the next animal. During the second task, the child was shown a picture of a cartoon turtle flat on a table. The child was asked, ‘‘What animal is this?’’. Once the child identified the animal, the experimenter pointed to the turtle’s feet and said, ‘‘Look! These are the turtle’s feet! Can you say feet?’’. Once the child saidfeet, the experimenter then said, ‘‘Can you show me
where the turtle’s feet are?’’. Then, the experimenter pointed to the turtle’s shell and said, ‘‘Look! This is the turtle’s shell! Can you say shell?’’. Once the child saidshell, he or she was asked again to point to the shell of the turtle on the picture. This was done to confirm that the child was able to name the part of the animal and was able to identify its location on the picture. The experimenter then took a blank card and held it perpendicular to the picture of the turtle, splitting the turtle so that the feet were only visible to the child and the shell was only visible to the experimenter. The child was asked, ‘‘What part of the turtle canIsee?’’, while the card was rotated so that opposite parts were visible to the child and experimenter. The child was asked the same question about the next part (feet). Children were given a score of 1 if they responded with the name of the correct animal on the first task and=or the correct part of the turtle visible to the experimenter on the second task. The maximum possible total score was 4.
The administration of the ToM tasks was counterbalanced. Twenty-five percent of the data for ToM tasks was re-coded by a second coder to ensure reliability. Intercoder reliability was
j¼1.0 for all tasks.
Results and Discussion
The descriptive statistics for the MLQ are depicted in Table 1. To examine the sequence of internal-state word acquisition, a 2 (gender)6 (word category) mixed-factorial analysis of vari-ance (ANOVA) revealed a significant main effect of word category,F(5, 312)¼50.42,p<.001,
g2¼.50. Specifically, pairwise comparisons with Bonferroni corrections, F(6, 47)¼40.61, p<.001,g2¼.84, revealed that children produced Perceptual and Volitional words the most,
followed by Emotional and Physiological words (p<.05). Children produced Moral and Cognitive words the least (p<.05).
Table 2 contains the mean percentages of correct responses (and standard deviations) for the ToM tasks. Across tasks, children succeeded on about half of the trials. Pearson correlations revealed no significant associations between gender and the ToM tasks or internal-state words. In addition, the three ToM tasks were not significantly correlated with one another,r(54)¼
.12–0.18,p¼.09–.345. However, age was significantly correlated with the visual
perspective-taking scores, r(66)¼.51, p<.001, and with the production of Perceptual, Physiological, Cognitive, and Moral words, r(54)¼.29, p<.05; r(54)¼.24, p<.05; r(54)¼.37, p<.01,
TABLE 1
Mean Percentage (and Standard Deviation) of Words in Each Category of the Mental Lexicon Questionnaire in Experiment 1
Category M SD
Physiological 67.1 25.1
Volitional 76.2 26.5
Perceptual 78.9 22.7
Emotional 71.0 23.2
Moral 46.9 25.7
Cognition 40.8 32.2
Total MLQ 58.3 18.8
respectively. Age tended toward significance with the Emotional and Volitional words,
r(54)¼.22, p<.10; r(54)¼.21, p<.10. Given these findings, age was partialled out of the analyses examining the association between the production of internal-state words and children’s ToM skills.
Relations Between Internal-State Language and Theory-of-Mind Skills
To examine the relations between internal-state vocabulary and ToM skills, bivariate and partial Pearson correlations were conducted on the proportion of internal-state words produced in each category and on the scores in each of the ToM tasks (see Table 3). The score on the emotional perspective-taking task was significantly correlated with both the proportion of Emotional words and Total internal-state vocabulary. Moreover, a trend emerged between emotional perspective-taking and the Physiological category of internal-state words. The understanding of desires was significantly correlated with the production of Volitional and Cognitive words. Finally, a significant relationship emerged between the visual perspective-taking scores and all of the internal-state word categories, including total internal-state vocabulary production.
The results from Experiment 1 demonstrate that the size of children’s total internal-state
vocabularyis significantly and specifically related to their concurrent understanding about visual and emotional perspectives, but less so for desires. In addition, the findings revealed that there were no relations between the standard ToM tasks, consistent with previous research in which no coherence among tasks was observed in toddlers (e.g., Carlson et al., 2004). These findings
TABLE 3
Bivariate and Partial Correlations (Controlling for Age at 30 Months) Between the Theory-of-Mind Tasks and Mental-State Language in Experiment 1 (N¼54)
Category
Emotional perspective-taking Desire Visual perspective-taking
Bivariate Partial Bivariate Partial Bivariate Partial
Physiological .21t .22t .06 .04 .40 .34
Volitional=Ability .05 .05 .25 .24 .37 .31
Perceptual .09 .10 .20t .19t .36 .27
Emotional=Affect .30 .31 .09 .08 .38 .32
Moral .07 .08 .13 .12 .44 .38
Cognition .06 .07 .24 .23 .52 .42
Total MLQ .24 .24 .15 .15 .34 .37
t¼trend,p<.10.p<.05. p<.01.
TABLE 2
Mean Percentage (and Standard Deviation) of Correct Responses on the Theory-of-Mind Tasks in Experiment 1
Theory-of-mind tasks M SD
Emotional Perspective-Taking 55.7 21.4
Desire 51.9 38.8
Visual Perspective-Taking 42.1 35.3
add an initial contribution to both the ToM and language literatures. However, there are important limitations to the current experiment. First, children’s general language skills have consistently been shown to be related to their ToM abilities (e.g., Milligan, Astington, & Dack, 2007). Because children’s general language abilities were not assessed, the observed relations between ToM skills and internal-state vocabulary may have been confounded by general language skills. Second, the understanding of desire was assessed with Repacholi and Gopnik’s (1997) desire task, which seems to be a problematic task when administered to older children (Carlson et al.). In their original study of desires in 14- and 18-month-old infants, Repacholi and Gopnik found that 69% of the children were successful in identifying another’s desires at this age. Carlson
and colleagues examined 24- and 39-month-old infants’ desires using the same task. Because these children were older than in the original study, high success rates on the task were expected. However, only 49%of the 24-month-olds and 69%of the 39-month-olds were successful in their
study, despite the children’s age advantage. In the current sample, only 52%of the 31-month-old
children were successful. Thus, it was deemed necessary to examine children’s understanding of desires using a different task in relation to their internal-state vocabulary (Wellman & Liu, 2004). With respect to the aforementioned limitations, a second experiment was conducted to address these methodological issues. In Experiment 2, a desire task assessing children’s comprehension of their own versus others’ desires was utilized. Given the significant link between visual perspective-taking skills and internal-state vocabulary observed in Experiment 1, children’s vis-ual perspective-taking skills were also examined in the second study. Finally, general language skills were controlled for in this sample.
EXPERIMENT 2
Method
Participants
Seventy-five (35 females, 40 males) 30-month-olds (Mage¼2;6 years; SD¼0.39 months;
range¼2; 5–2;7 years) participated in this cross-sectional study. Participants were all White middle-class German speakers, living in a large city in South Germany. The children were orig-inally recruited using birth lists as part of a longitudinal study on precursor abilities of a ToM when they were 7-months-old. Given that this sample was a subsample from a longitudinal study, a narrower age range was used to avoid age effects observed across measurement points. Thus, no age effects occurred for any of the measures.
Procedure
Children were tested in a laboratory equipped with cameras. All tasks were videotaped. Each observation began with a familiarization period, during which the experimenter interacted with the child. During this time, the mothers completed the MLQ. They were asked through written and verbal instructions to indicate as many words as they had heard their child say and to provide examples for their responses.
Mental Lexicon Questionnaire (MLQ). The German version of the MLQ used in this study was adapted from the English Internal-State Checklist by Bretherton and Beeghly (1982). How-ever, some terms could not be adapted. For instance, the translation equivalent of the mental-state term ‘‘sleepy’’,. . .which is quite common among English-speaking children (see Bretherton &
Beeghly), is not typically used by German children at this age. Rather, children use the verb ‘‘tired’’ to express sleepiness. Consequently, ‘‘sleepy’’ was not included in the German MLQ. Moreover, the Emotion term ‘‘mad’’ is identical to the translation equivalent of ‘‘angry,’’ the Moral term ‘‘must’’ is identical to ‘‘have to,’’ and the Cognition term ‘‘may’’ has no translation equivalent in German. Thus, these two terms were excluded. A further issue is that German chil-dren use the translation equivalent of ‘‘to sleep’’ to express that someone is ‘‘asleep,’’ while they use the German translation equivalent of ‘‘wake’’ to express that someone is awake. The same is true for ‘‘hear’’ and ‘‘listen,’’ as well as ‘‘hungry’’ and ‘‘starving,’’ and ‘‘cold’’ and ‘‘freezing.’’ Thus, the pairs ‘‘sleep’’ and ‘‘asleep,’’ ‘‘wake’’ and ‘‘awake,’’ ‘‘hear’’ and ‘‘listen,’’ ‘‘hungry’’ and ‘‘starving,’’ and ‘‘cold’’ and ‘‘freezing,’’ although all included in the questionnaire, were treated as one item, respectively. Finally, ‘‘have to’’ is not a volition or ability term in German and was thus excluded from this category, while the German Volition termmoechtewas added. In sum, the final version of the German adaptation of the MLQ included 69 internal-state terms from six different categories: Perception terms (11 terms), Physiology terms (6 terms), Volition=Ability terms (5 terms), Emotion=Affect terms (27 terms), Moral terms (8 terms), and Cognition terms (12 terms). As in Experiment 1, the discrepancy in the number of items across the different MLQ language versions was addressed by using the proportion of words that toddlers used in a category relative to the total number of words in that category.
Diverse desire task. Given the age of the toddlers, the easiest task from the Wellman and Liu (2004) scale (Diverse Desires) was included in this study. At a narrow table, children were presented with a Playmobile toy figure of an adult and a laminated sheet of paper with a drawing of a carrot and a cookie. First, the children were told the following story: ‘‘Here is Mr. Mueller (typical German surname). It’s snack time, and Mr. Mueller wants to eat something. Here are two different snacks: a carrot and a cookie. Which snack would you like best? Would you like a carrot or a cookie best?’’ (own-desire question). If the children chose the carrot, the experimenter pro-ceeded as follows: ‘‘Well, that’s a good choice, but Mr. Mueller really likes cookies. He doesn’t like carrots. What he likes best are cookies.’’ If the children chose the cookie, they were told Mr. Mueller liked carrots. Then the children were asked the target question: ‘‘So, now it’s time to eat. Mr. Mueller can only choose one snack, just one. Which snack will Mr. Mueller choose? A carrot or a cookie?’’. To be scored as correct, the children had to provide an answer to the target question (either verbally or by pointing to the right picture) that was different from their answer to the own-desire question. Children could receive a dichotomous score of either 0 or 1.
Visual perspective-taking task. The perspective-taking task was modeled after McGuigan and Doherty (2002). Overall, children completed two trials with four test questions. On the first trial (180trial), the experimenter sat opposite the children at a narrow table (both experimenter
and child were seated on chairs). A Winnie the Pooh toy doll (10 cm5 cm3 cm) and a card-board screen (18 cm high23 cm wide) with an attached wooden base were placed on the table. The experimenter then placed the cardboard screen with the broad side turned toward herself, in such a way that the bear was blocked from her view, but in clear sight of the child. The child was asked: ‘‘Can I see the bear now?’’ (correct answer¼no) and ‘‘Can you see the bear now?’’
(correct answer¼yes). Then, the experimenter placed the cardboard screen broadside toward the child, so that the bear was blocked from the children’s view but in clear sight of the experimenter. Again, the child was asked: ‘‘Can I see the bear now?’’ (correct answer¼yes) and ‘‘Can you see the bear now?’’ (correct answer¼no). Depending on the trial, children’s correct answers could either involve a verbal answer (i.e., ‘‘yes’’ or ‘‘no’’), or a nod or a head shake. Children received a score of 1 for correct responses and a score of 0 for incorrect responses. Thus, across the two trials, children could receive a maximum score of 4. Consistent with Experiment 1, the percentage of children’s correct answers were used in all analyses.
For both tasks, 30%of the data were re-coded by a second coder to ensure reliability.
Inter-coder reliability wasj¼1.0 for all tasks.
General language skills. A limitation to Experiment 1 was that children’s general language abilities were not assessed. Thus, it is possible that the associations found between children’s internal-state vocabulary and their perspective-taking skills and desire comprehension may have been confounded by their general language abilities. Therefore, a measure of children’s general expressive language abilities was included to serve as a control variable on the sample of German-speaking children. At 30 months, children were administered the ‘‘vocabulary’’ subtest of the Kaufmann Assessment Battery (Kaufman & Kaufman, 1983) for children aged 2;6 to 11;0. Children were shown pictures of 24 objects that they had to label (e.g., a banana, scissors, ear, ladder, zipper). For each correct answer, children received a score of 1, while for each incorrect answer, children received a score of 0. Standardized scores were used in all analyses.
Results and Discussion
The means and standard deviations for the production of internal-state words can be found in Table 4. A 2 (gender)6 (word category) mixed-factorial ANOVA revealed a significant main effect of gender, F(1, 67)¼8.06, p<.01, g2¼.11, and word category, F(5, 335)¼142.89, p<.001, g2¼.68. Overall, girls produced more internal-state terms. Thus, gender was
con-trolled for in all subsequent analyses involving children’s internal-state vocabulary. Specifically, pairwise comparisons using Bonferroni corrections revealed that the order of acquisition of internal-state words among German toddlers was consistent with findings from Experiment 1. German children mainly produced Physiological, Volition=Ability, and Perception terms,
TABLE 4
Mean Percentage (and Standard Deviation) of Words in Each Category of the Mental Lexicon Questionnaire in Experiment 2
Category M SD
Physiological 90.82 12.95
Volitional 84.06 22.64
Perceptual 79.45 17.20
Emotional 55.77 21.47
Moral 55.25 32.75
Cognition 33.33 27.00
Total MLQ 60.68 19.95
followed by Emotional and Moral words (p<.05). Children’s production of Cognition terms lagged significantly behind the production of terms from any other word category (p<.05). No significant age effects emerged in the analysis.
Seventy-one children (33 females, 38 males) completed the desire task (n¼4 children were excluded due to noncompliance), and 47.9%of the children correctly distinguished own versus
other desire. No significant gender or age differences emerged.
Out of the original sample of 75 children, due to fussiness, 4 children were not administered the task and 4 children had to be excluded because of missing trials. Thus, 67 children (34 females, 33 males) participated in the visual perspective-taking task (M¼77.11%, SD¼19.67%,
range¼25%–100%). Significant gender differences emerged in which girls performed
signifi-cantly better (M¼82.11%,SD¼17.06%) than did boys (M¼71.97%,SD¼21.12%),t(65)¼
2.16,p<.05. Pearson correlations revealed that children’s competence at the desire task and the visual perspective-taking scores were not significantly correlated with one another,r(66)¼
.07,p¼.592.
Control Measure: General Productive Language Skills at 30 Months
Children (N¼74; 35 girls, 39 boys) received a mean score of 103.04 (SD¼12.82, range¼73–136) on the language test. No significant gender differences emerged. Listwise Pearson correlations (N¼61) revealed that children’s general language skills were significantly related to their MLQ scores, r¼.34, p<.01, and visual perspective-taking skills, r¼.29,
p<.05, but not to children’s competence in the desire task,r¼.11, p¼.402.
Relations Between Internal-State Language and Tom Skills
Bivariate and partial Pearson and point biserial correlations, controlling for gender and general language skills were conducted on the data (see Table 5). The results revealed that all lexical categories in children’s internal-state vocabulary, including a global score, were signifi-cantly related to their visual perspective-taking skills. The relation between children’s desire
TABLE 5
Bivariate and Partial Correlations (Controlling for Gender and General Productive Language Skills) Between the Theory-of-Mind Tasks and Mental-State Language
in Experiment 2 (N¼57)
Category
Visual perspective-taking Diverse desire
Bivariate Partial Bivariate Partial
Physiological .27 .25 .22 .23
Volitional=Ability .46 .37 .11 .13
Perceptual .38 .23 .16 .19t
Emotional=Affect .48 .39 .14 .17
Moral .45 .37 .18t .18t
Cognition .41 .31 .18t .19t
Total MLQ .50 .40 .18t .20t
t¼trend,p<.10.p<.05. p<.01. p<.001.
scores and internal-state vocabulary revealed a trend for their total vocabulary, as well as with the Perceptual, Moral, and Cognitive category terms, while Physiology category terms were significantly related to children’s desire scores.
Taken together, the findings from Experiment 2 highlight a pattern of acquisition of internal-state words that is strikingly similar to the one observed in English-speaking children. These findings are also consistent with a recent study that has shown a similar internal-state verbal development among English- and French-speaking toddlers (Poulin-Dubois, Chiarella, et al., 2009). Regarding the association between children’s total internal-state vocabulary and children’s early explicit understanding of desire, analyses approached statistical significance, and there was a significant relation between children’s talk about physiological states and desire understanding. It is speculated that testing older children might yield stronger relations. Impor-tantly, as expected, strong associations between children’s developing internal-state vocabulary and their understanding of others’ visual perspective emerged in Experiment 2 after controlling for general vocabulary, replicating the findings from Experiment 1.
GENERAL DISCUSSION
In a groundbreaking paper published three decades ago, Bretherton and Beeghly (1982) documented that internal-state language emerges toward the end of the 2nd year. They argued that the mastery of language renders implicit ToM, observed during the preverbal stage (in communicative intentions), increasingly observable and explicit. Since then, the acquisition of internal-state language has been a line of research that has helped demonstrate that chil-dren as young as 3-years-old show some early evidence of false-belief understanding (Bartsch & Wellman, 1995; J. Dunn, 1988). Furthermore, a progression from reasoning about desires (as well as perceptual awareness and emotional experience) to later reasoning about beliefs has also been revealed in children’s everyday conversations (J. Dunn & Brown, 1991; Well-man, Harris, Banerjee, & Sinclair, 1995). Since this pioneer work, researchers have documen-ted a developmental progression in understanding the mind in tasks that require explicit reasoning (Wellman & Liu, 2004). They have also documented infants’ understanding of internal states such as intentions, emotions, and beliefs, although belief understanding in infancy is still contested (Poulin-Dubois, Brooker, & Chow, 2009; Sodian, 2011; Wellman, 2010).
In this study, we provide three main contributions to the research on early ToM development. First, we examined the concurrent association between internal-state vocabulary and ToM abilities in toddlers. In Experiment 1, coherence between a range of words in internal-state vocabulary, visual perspective-taking skills, and emotion understanding emerged at 30 months. Specifically, the strongest relations emerged between the understanding of visual perspectives and internal-state vocabulary. This association held even when general language skills were controlled for in Experiment 2. Second, unlike previous studies, we examined all categories of mental words and found that all types of words were associated with visual perspective-taking skills. Third, the distribution of mental words across categories originally reported by Bretherton and Beeghly (1982) was also observed in German-speaking children, replicating and extending previous work on internal-state language acquisition in French-speaking children (Poulin-Dubois, Chiarella, et al., 2009).
The usage of internal-state language, as monitored through conversational cues, has been linked to a number of variables, including reciprocal play and attachment style (Lemche, Kreppner, Joraschky, & Klann-Delius, 2007; Mcquaid, Bigelow, McLaughlin, & MacLean, 2008; Meins & Fernyhough, 1999). More importantly, both concurrent and predictive positive correlations have been found between the amount of preschoolers’ internal-state language usage and their ToM skills (L. M. Dunn & Dunn, 1981; Hughes & Dunn, 1998; Nielsen & Dissanayake, 2000). Although monitoring children’s internal word usage has revealed a number of positive associations, less investigation has been placed on children’s internal-state vocabulary, despite the fact thatvocabularyallows one to grasp the richness of children’s internal language. Moreover, investigating a range of internal-state word production allows for a better understanding of how it may be reflecting different ToM concepts (e.g., emotions, desires, beliefs).
The only studies that have compared ToM performance and internal-state vocabulary concur-rently found no link at 18 and 24 months between the understanding of desires, intentions, visual perception, and internal-state vocabulary, although a significant correlation emerged between the comprehension of pretense and internal-state language at 24 months (Carlson et al., 2004; Repa-choli & Gopnik, 1997). These null results are surprising given that intention understanding in infancy has been found to predict internal-state vocabulary around 30 months of age, and that internal-state vocabulary in toddlers predicts later ToM skills (Olineck & Poulin-Dubois, 2005, 2007). Moreover, given the lack of coherence of ToM performance using standard ToM measures but significant associations between internal-state vocabulary between 2 and 3 years of age and behavioral ToM skills, the current findings suggest that children’s internal-state vocabulary provides a valid measure of ToM skills. This is illustrated by the finding that chil-dren’s global internal-state languagevocabularyshows an emerging concurrent relationship with the understanding of emotions and visual perspectives. Importantly, a strong relation emerged between the ability to reason about others’ visual perspectives and all categories of internal-state vocabulary, including a global internal-state vocabulary score, in Experiment 1. These findings remained strongly significant even when controlling for general language abilities in Experiment 2, revealing that this association was specific to internal-state vocabulary. The current findings are consistent with Harriss’ simulation theory (1992, 1996), stressing the importance of language in the development of perspective-taking skills. Further, this study extends the results of B. M. Farrant and colleagues (2006), who found relations between language impairment and Level 2 perspective-taking skills, demonstrating very specific relations between normally developing children’s internal-state vocabulary skills and Level 1 visual perspective-taking skills. Finally, the results are in line with previous studies showing a link between children’s ability to represent intangible, imaginary worlds in pretend play and internal-state vocabulary (Carlson et al., 2004). They also support Moore’s (2006) proposition that the early functional use of internal-state lan-guage, referring to propositional and intangible states, serves to clarify diverging mental per-spectives. Thus, at 30 months, children’s ability to learn words that refer to inner states is related to their concurrent understanding that people may have different and misleading percep-tual information.
Taken together, when age-appropriate ToM measures are used at 30 months, such as Level 1 visual perspective-taking, internal-state vocabulary and ToM skills are related and remain so when controlling for general language skills. The association between total internal-state words and desire understanding was not supported in the current sample. It is suggested that the Repacholi and Gopnik’s (1997) desire task used in Experiment 1, although it may reflect some
understanding of desire at 18 months of age (Repacholi & Gopnik), may not be suitable to examine desire understanding in 30-month-olds, as children may view this task as a pretend game. This seemed to be confirmed by other studies that have reported a decline in performance on this task between 18 and 24 months of age (Carlson et al., 2004). Nonetheless, when a more age-appropriate desire task was used in Experiment 2, which more readily assessed children’s conceptual understanding of desire, the association with children’s total internal-state word production became a trend. Taken together, these results suggest that with age, more of children’s ToM skills and their talk about psychological states may become increasingly interrelated, as accounted for by this trend.
Due to the correlational design used in the present study, the directionality of words and concurrent ToM concepts cannot be identified. As previously mentioned, studies have shown that early ToM understanding in infancy predicts internal-state vocabulary in toddlerhood (Olineck & Poulin-Dubois, 2005) and that vocabulary about the mind predicts later ToM skills (Olineck & Poulin-Dubois, 2007). However, given longitudinal data on language and ToM development (Astington & Jenkins, 1999), evidence strongly suggests that language abilities set the stage for children’s ToM competencies and not the reverse. The current study provides important insights on the relations between young toddlers’ concurrent internal-state vocabulary and development of precursor abilities of a ToM (more specifically, visual perspective-taking skills), independent of general language skills.
Another contribution of the current research is the demonstration of the remarkably similar sequence of acquisition of internal-state words across languages. The findings replicate a recent study showing the same level of consistency in English- and French-speaking children (Poulin-Dubois, Chiarella, et al., 2009). Despite a few discrepancies among the percentage of internal-state language categories, the internal lexicon of English-, French- and German-speaking children was mainly composed of Perceptual and Volitional words, with 70%to 80%of all the
words in that category already used. About 60%of the Emotional terms were in the children’s
lexicon, and Cognitive terms were even less represented at only 35%. This developmental
sequence parallels that reported in a scale of ToM tasks tested across many cultures, with desire understanding preceding belief understanding (Wellman, 2010; Wellman et al., 2006).
The current study is the first of its kind to demonstrate that children’s internal-state vocabu-laryis concurrently related to ToM abilities in young toddlers. Given the potential of internal-state language on predicting ToM skills, future studies examining precursors to ToM abilities should investigate toddlers’ developing internal-state vocabulary skills as they may serve as an important pathway to better mind understanding. If internal-state language becomes increas-ingly significant with children’s performance on a battery of ToM tasks as they get older, these findings would suggest that internal-state language is a good measure of children’s ToM skills. In addition, future research should address the link between internal-state vocabulary and a wide range of ToM tasks by using batteries of tasks designed for younger children and infants. The children in the current sample were at an age at which internal-state language is clearly devel-oping (they produced 58%to 60%of the words included in the MLQ), but also at which there is
a lack of available explicit ToM tasks appropriate to assess children’s ToM skills (but see Gopnik & Slaughter, 1991; O’Neil, 1996; Wellman, Cross, & Watson, 2001, for other ToM tasks that could be used with children aged 2- to 3-years-old). Thus, investigating younger children with implicit ToM tasks will allow for a better understanding of the relationship between these two abilities as they are developing, which have significant implications for
the development of programs to foster both internal-state language and ToM skills in young children. Finally, the current findings highlight that the associations between internal-state vocabulary and perspective-taking skills do not exist solely in English-speaking populations and that the acquisition of toddlers’ internal-state vocabulary is consistent across different linguistic groups. It will be crucial for future studies to examine internal-state vocabulary across various linguistically diverse populations to better understand how the production of internal-state words develops within and across cultures.
ACKNOWLEDGMENTS
This research was supported by: Le Fonds Que´be´cois de la Recherche sur la Socie´te´ et la Culture and the Social Sciences and Humanities Research Council of Canada for grants awarded to Diane Poulin-Dubois; the German Research Council for a grant awarded to Beate Sodian; and le Fonds que´be´cois de la recherche sur la socie´te´ et la culture, the Centre for Research in Human Devel-opment, and the Social Sciences and Humanities Research Council of Canada, which awarded graduate fellowships to Sabrina Chiarella to help fund the project.
All authors would like to extend their gratitude to Dr. Petra Hauf and Dr. Elena Geangu for their collaboration on this project, including data collection in Antigonish, Nova Scotia, as well as Dr. Paul Hastings. Authors S. S. C. and D. P.-D. would also like to thank Amanda Aldercotte and Marie-Pier Gosselin for their help in data collection and coding. Authors S. K. and B. S. would also like to thank their lab manager Sabrina, as well Hannah Eisenbeis, Maria Vuori, and all the student assistants in the baby lab. Finally, the authors would like to express their gratitude to the research participants whose contribution made this project possible.
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