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The Journal of Deaf Studies and Deaf Education The Development of the Ability to Recognize the Meaning of Iconic Signs Tammy D. Tolar, Amy R. Lederberg, Sonali Gokhale and Michael Tomasello J. Deaf Stud. Deaf Educ. 13:225-240, 2008. First published 7 Sep 2007; doi:10.1093/deafed/enm045

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The Development of the Ability to Recognize the Meaning of Iconic Signs Tammy D. Tolar Amy R. Lederberg Sonali Gokhale Georgia State University, Atlanta Michael Tomasello Max Planck Institute for Evolutionary Anthropology, Leipzig

Early developmental psychologists viewed iconic representation as cognitively less complex than other forms of symbolic thought. It is therefore surprising that iconic signs are not acquired more easily than arbitrary signs by young language learners. One explanation is that children younger than 3 years have difficulty interpreting iconicity. The current study assessed hearing children’s ability to interpret the meaning of iconic signs. Sixty-six 2.5- to 5-year-olds who had no previous exposure to signs were required to match iconic signs to pictures of referents. Whereas few of the 2.5-year-olds recognized the meaning of the iconic signs consistently, more than half of the 3.0-year-olds and most of 3.5-year-olds performed above chance. Thus, the ability to recognize the meaning of iconic signs gradually develops during the preschool years. Implications of these findings for sign language development, receptive signed vocabulary tests, and the development of the ability to interpret iconic symbols are discussed.

Iconic symbols are a common means of communication. They are prevalent because individuals can interpret them without requiring a prior explicit connection between them and their referents. The features or actions portrayed by iconic symbols can generate mental representations and associations that often match or come very close to the idea the presenter of the icon is intending to convey. The classic example of this aspect of iconicity is the game charades. This is not true of arbitrary symbols, for which meanings have to be explicitly made either by associNo conflicts of interest were reported. Correspondence should be sent to Tammy D. Tolar, Department of Educational Psychology & Special Education, PO Box 3979, Georgia State University, Atlanta, GA 303023979, ([email protected]).

ation or definition. For this reason, iconic representations are considered relatively easy to recognize and learn as symbols. Early psychologists identified iconic representation as a precursor to the development of arbitrary symbols. More specifically, Werner and Kaplan (1963) viewed iconic gestures as one of the first forms of representation in the developmental process of ‘‘distancing between person and symbolic vehicle’’ (p.44). They considered speech symbols the culmination of this process because the phonic form of representation could be ‘‘clearly differentiated from pragmatic– conative bodily mobility’’ (p. 45). In this view, the ability to understand iconic symbols precedes appreciation of arbitrary symbols. Peirce (1894) distinguished icons from symbols and considered icons a more rudimentary form of communication. He argued that an iconic representation has no connection to its referent in the mind, although its presentation would ‘‘excite analogous sensations’’ in the mind. On the other hand, a symbol is connected to its referent in the mind ‘‘by virtue of the idea of the symbol-using mind.’’ The implication of Peirce’s beliefs about iconic and symbolic representations is that different mental processes are used in their interpretation. However, the line between icon and symbol and the mental processes associated with them can be blurred because once an icon is conventionalized it becomes a symbol. In fact, Peirce argues that symbols often grow from icons. The view that different mental processes are involved in interpreting iconic and symbolic representations

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doi:10.1093/deafed/enm045 Advance Access publication on September 7, 2007

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and that the processes involved in interpreting icons are less taxing or complex than those required to understand arbitrary symbols has influenced how sign language has been conceptualized. Both sign and oral languages share many of the features that by definition make them languages, such as symbolic representation and syntactic structure. However, one aspect of symbolic representation, iconicity, may distinguish the two language forms, and the potential for iconicity in sign languages has been a source of some debate. The traditional view is that oral languages have very little iconicity whereas many of the seemingly mimetic gestures in sign languages are inherently iconic. A higher degree of iconicity in sign language suggests relative ease of acquisition. However, in the past, sign linguists have generally downplayed the role of iconicity (Schick, 2006; Wilcox, 2004). This is at least partially due to the way in which both ‘‘abstract’’ oral and ‘‘iconic’’ gestural symbols have been perceived. Similar to early philosophers and developmental psychologists who viewed the meaning in iconic representations as transparent and related more to perceptual than cognitive abilities, early linguists viewed the iconicity in sign language as evidence that signs were not worthy of the term ‘‘language.’’ More recently with the acceptance of sign languages as true languages, such a view has been challenged. Scholars have recognized that iconicity is a legitimate, and interesting, aspect of linguistic systems (Pietrandrea, 2002; Taub, 2001). In fact, the relative lack of iconicity in oral languages may be more a function of the limitations of the medium than an indictment against iconicity as an inherent part of language and abstract thought. Linguistic analysis suggests that iconic associations are a significant part of handshapes and body locations of many signs (for an analysis, see Pietrandrea, 2002). In addition, some signs are transparently iconic and represent features or actions of the referent (Campbell, Martin, & White, 1992). Evidence suggests that nonsigning adults can spontaneously perceive the meaning of these iconic signs (Klima & Bellugi, 1979; Pizzuto & Volterra, 2000). In addition, iconicity seems to facilitate learning of sign language among adults. For example, adults learning signs for the first time are more likely to retain iconic than

noniconic signs in short- and long-term memory (Beykirch, Holcomb, & Harrington, 1990; Lieberth & Gamble, 1991). Evidence concerning the role of iconicity in young children learning to communicate is contradictory. As Werner and Kaplan (1963) noted, initial gestures that toddlers acquire are almost all iconic. However, Namy, Acredolo, and Goodwyn (2000) argue this apparent preference for iconic gestures is due to parental modeling of iconic rather than arbitrary gestures. Children learning sign language are exposed to both iconic and arbitrary gestures (i.e., signs), and in this situation, there is no preference for learning iconic signs (Folven & Bonvillian, 1991; Orlansky & Bonvillian, 1984). During the first 18 months, only one-third of signs produced by hearing children of deaf parents are iconic. Based on this and their own observations, Newport and Meier (1985) conclude: ‘‘there is an abundance of evidence that iconicity in general plays a minor role, if any at all, in the course of ASL acquisition. (though) iconicity does play a role in the acquisition of individual signs by older children and adults’’ (p. 889). What is the source of this developmental change? One explanation is that young children who are acquiring American Sign Language (ASL) through native input may process signs as arbitrary symbols because they are learning their first language. Indeed, skilled signers seem to process signs at the level of their linguistic representations (phonemes) and ignore pictorial aspects (Siple, Caccamise, & Brewer, 1982). However, it also might be that the meaning of iconic signs are only transparent to older children because iconic representation is a cognitively advanced skill not readily available to young language learners. Research with hearing children suggests the latter may be true. Hearing children’s appreciation for iconicity has been explored in experimental studies, which suggest that the ability to interpret iconic gestures undergoes developmental change during early childhood. Hearing children (26 months old) show a preference for learning iconic over arbitrary gestures but 18-month-olds do not (Namy, Campbell, & Tomasello, 2004). Tomasello, Striano, and Rochat (1999) found that 18- and 26-months-old were able to select the correct referent for iconic gestures but only when

Spontaneous Recognition of Iconic Signs 227

the gesture had been modeled in the context of using an object (e.g., hammering with a hammer). It was not until 35 months that children recognized iconic gestures that were not modeled just prior to the experimental task. Tomasello et al. suggested that the younger children’s performance may be based on associations between gesture and object made during the demonstration, rather than iconic recognition. However, Striano, Rochat, and Legerstee (2003) found 26-month-olds (but not 18-month-olds) were able to spontaneously select a referent based on presentation of an iconic gesture even if the referent and its associated action had not been modeled prior to the task. It is not clear, however, if this is done because the children appreciate the iconic representation in the gestures. The iconic gestures used in these studies could be interpreted through metonymic processes in the sense that they represent part of an ‘‘activity scheme’’ that includes both the action and the object (Tomasello et al. 1999). For example, in a familiar routine such as using a hammer, the motion of hammering may act as a signal to enact the entire routine including retrieving the hammer. In this view, iconic gestures are not treated as symbols nor do they tap the same cognitive processes used by adults in deriving meaning from iconicity. The objects and gestures in the Striano et al. study were highly conventional (e.g., hammer, brush), so by 26 months the children were likely to have had enough experience to have activity schemes associated with these objects. Regardless of what is influencing young children’s ability to respond to iconic gestures, before 35 months, performance is relatively low (e.g., 50%–60% success rates), suggesting that this ability is not very robust. In fact, 3-year-olds in the Tomasello et al. study and 4-year-olds in the Namy et al. study performed markedly better than 18- and 26-month-olds in taking advantage of iconicity. The research in iconic gestures supports the notion that the meaning of iconic signs would not be transparent to young children acquiring sign language, at least not until 3 years of age. However, iconic signs differ from iconic gestures in multiple ways (e.g., representation of static as well as action features, linguistic constraints on sign formation). The goal of the current study was to directly examine the development of the ability to interpret iconic signs. White and

Tischler (1999) conducted such a study with older children. Using a forced choice picture task similar to the Peabody Picture Vocabulary Test (PPVT; Dunn & Dunn, 1997), they asked children to select pictures that corresponded to the meaning of ASL signs. First-, fourth-, and ninth-grade hearing students who had no exposure to sign identified the correct referent over 70% of the time. Thus, iconic signs were transparent by first grade. Based on research of other iconic symbol systems, we hypothesized that this ability would develop some time between 2.5 and 3.5 years of age. Researchers have explored hearing children’s ability to use such iconic symbols as physical replicas and pictures (Callaghan, 1999; Callaghan & Rankin, 2002; DeLoache, 1991, 2002; Tomasello et al. 1999). This research suggests that the ability to interpret iconic symbols is fragile before 3 years of age, even for such transparent representations as pictures and physical replicas. We tested the development of this ability in hearing, rather than deaf children because hearing children’s performance would not be confounded by exposure to sign. However, in order to generalize the results to deaf children and understand the underlying mechanisms involved in iconic representation, we assessed the role of language in the children’s ability to interpret iconic sign. First, we examined if the ability to recognize iconic signs among young children was a function of vocabulary level more than general cognitive development. Second, we assessed whether language served as a mediator in the development of the ability to interpret iconic symbols. Callaghan (2000) found that 2.5- and 3.0-year-olds were able to interpret the meaning of pictures only in conditions when words could be used as mediators. Attributing meaning to an iconic symbol using language may tap different cognitive processes than those involved in directly mapping an iconic symbol to its referent (Callaghan, 2000; Campbell et al. 1992). These processes may be additive and together produce better performance than either process alone. Callaghan suggested that young children may require both processes in order to recognize iconic symbols. Therefore, we investigated whether or not producing an accurate label for a referent influences performance

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in identifying iconic signs and whether or not this influence is similar throughout development among preschool-aged children. If language proves to be an important factor in hearing children’s ability to interpret iconic signs, then the results would generalize to deaf children who have comparable levels of language to the hearing children, regardless of age. In other words, if language helps mediate interpretation of iconic signs, the ability to perceive iconicity may relate more to a child’s language abilities than age or cognitive development. For deaf children who are language delayed, this ability may develop at a later point in development than what is evident in this study or in deaf children of deaf parents. Finally, we investigated if the way in which a sign depicts a referent influences comprehension of iconic signs. Iconic signs differ in terms of what aspects of the referent are represented. For this study, we developed a classification system based on the degree to which iconic signs involved representations of action versus representations of static features. Pantomimic (Pn) signs primarily depict actions associated with the referent. For example, one variation of the ASL sign for TOWEL mimics the action of using a towel by rubbing the face in circular motions with flat hands. Perceptual (Pr) signs primarily depict static features of a referent. The sign for EYEGLASSES uses the forefingers and thumbs of both hands to mimic the shape of glasses on the signer’s face. Finally, some signs represent both (B) perceptual and pantomimic aspects of the referent. The sign for CAMERA depicts both the shape of a camera and the action of taking a picture. As Schick (2006) points out, the ability to appreciate iconicity may not be ‘‘all or none.’’ We hypothesized that children will understand action-based iconicity before feature iconicity. Most iconic gestures used by hearing toddlers and young children come from motor routines depicting actions by or on referents (e.g., brushing hair, using a hammer), suggesting action-based gestures may be primary (Acredolo, Goodwyn, Horobin, & Emmons, 1999; Werner & Kaplan, 1963). In addition, Schick found that size and shape specifier (SASS) classifiers, which represent the visual-geometric features of object, were acquired relatively late in development.

Methods Participants Sixty-six children (32 girls and 34 boys) were recruited from three preschools and were selected because they were within one of six predetermined age ranges. There were fourteen 2.5-year-olds (M 5 31 months, range 5 30–32 months); fifteen 3.0-year-olds (M 5 37 months, range 5 36–38 months); fifteen 3.5-year-olds (M 5 43 months, range 5 42–44 months); eleven 4.0-year-olds (M 5 49 months, range 5 48–50 months); five 4.5-year-olds (M 5 55 months, range 5 54–56 months); and six 5.0-year-olds (M 5 62 months, range 5 61–62 months). During data collection, it became evident that the children in the 4.5 and 5.0 groups were able to perceive the iconicity in a majority of the signs, so we focused our efforts on increasing the number of participants in the younger groups. Because the 4.5 and 5.0 groups consisted of fewer children who performed at similar levels we combined them into one group for all analyses. The children were mostly white and middle to upper middle class. Nine children (eight 2.5-year-olds and one 3.0-year-old) were excluded from the study. Three of the 2.5-year-olds refused to finish the language assessment. Four of the 2.5-year-olds and the 3.0-year-old completed the language assessment but did not want to return to the testing room for the Sign Test. One 2.5-year-old did not understand the sign task.

Materials The PPVT-III (Dunn & Dunn, 1997) is a test of receptive vocabulary normed for children as young as 2.5 years. In addition to providing a language age, it served as a control task to ensure the children could do a symbolic picture task. The test has high internal reliability (lowest alpha 5 .93 for 2.5- and 3.0-year age groups) and test–retest reliability (corrected coefficient 5 .92 for 2.6 – 5.9 years). The PPVT consists of picture plates each of which contains four black-and-white drawings. The examiner asks the child to select the picture that represents a particular word (e.g., ‘‘Show me dog. Which one is dog?’’). The Sign Test was developed for this study and consisted of iconic signs from ASL. In this task,

Spontaneous Recognition of Iconic Signs 229

tion was based on two criteria: iconicity and sign type. We initially selected 76 signs that we perceived to be iconic. Sign iconicity was determined through two studies with adults who had no knowledge of sign language. Using plates from the CPVT, adults were asked to select the correct referent for the signs. We ranked the signs according to the percentage of adults who could match them to pictures of their referents.1 To meet the second criteria for selection, sign type, we categorized signs as perceptual, pantomime, or both perceptual and pantomime as described in the Introduction. Signs rarely purely represent the action or features of the referent. Therefore, our distinctions between different types of signs were based on the aspects of the referents that are most emphasized by the iconic signs. We selected 10 of the most iconic signs based on the adult performance from each category. Finally, from the remaining signs we chose six signs for practice so that the children could experience two of each type of sign in order to understand the nature of the task. More than half of the test signs were recognized by 100% of the adults tested. The least iconic test sign was recognized by 96% of the adults. Table 1 shows the signs used in this study and the percentage of adults who correctly matched the sign to the referent. Twenty-three of the signs are from the CPVT. In the final version of the test booklet, the pages were randomly ordered, and the target pictures were equally distributed between the four quadrants on the pages. A group of adults (N 5 43) was tested on the

Figure 1 A page from the sign task booklet. The target picture on this page is BALL.

participants were required to match each sign to one of four black-and-white drawings. The four drawings were on an 8.50 3 110 sheet of paper in a booklet created from the Carolina Picture Vocabulary Test (CPVT, Layton & Holmes, 1985). The CPVT is a vocabulary test modeled after the PPVT to provide a normed test of receptive vocabulary for deaf children acquiring sign. A page from the Sign Test booklet is shown in Figure 1. We selected 30 test and 6 practice signs because we estimated this was the maximum number of signs we would be able to test with young children. Sign selec-

Table 1 Sign Test signs and percent of adults who matched sign to referent Pantomime only signs

n

Percent match

Perceptual only signs

n

Percent match

Pantomime and perceptual signs

n

Percent match

BABY EAT MIX PERFUME SEWING TISSUE WRITE BASEBALL HAMMER TOWEL HAT COLD

70 29 29 29 29 29 29 70 70 99 99 29

100 100 100 100 100 100 100 99 99 98 97 97

HOUSE LOOK NARROW VASE GLASSES TIGER SHOWER GLOBE SMOOTH TORNADO BOX BALL

29 29 29 29 70 99 70 29 29 99 99 70

100 100 100 100 99 97 97 97 97 96 94 94

BIKE TELEPHONE CAMERA CATERPILLAR NEEDLE BANANA ICE CREAM RING WINDOW MIRROR JAR BOOK

70 70 29 29 29 70 70 70 70 99 99 70

100 100 100 100 100 99 99 99 97 94 95 93

Note. Adults matched signs to pictured referents in the first (n 5 29), the second (n 5 70), or both (n 5 99) studies.

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30 test signs from the same test booklet used in the children’s study. The mean performance of this group was 96.2% (SD 5 3.2%).

Procedure The children were tested in quiet, well-lit rooms at their preschools in two 30-min video-taped sessions. The PPVT was administered during the first session, and approximately a week later, the sign task was given. The children were randomly selected to be in one of two conditions for the sign task. In the labeling condition, the person administering the test would point to each drawing on the picture plate and ask the child, ‘‘What is this?’’ A correct label was confirmed with a nod and a verbal affirmative. If the child mislabeled the indicated picture or did not respond, the researcher would reply with a positive comment and provide the correct label (e.g., ‘‘Good guess, but this is a caterpillar.’’). In the nonlabeling condition, the examiner would point to each picture and say, ‘‘Look at this one,’’ to make sure the child attended to each of the four drawings on the page. In both conditions, the practice signs were presented first. For both the practice and test signs, after the researcher directed the child’s attention to each of the four pictures, she would draw the child’s attention to herself (e.g., ‘‘Look at me.’’), perform the iconic sign and say, ‘‘Show me this one. Which one is this?’’ If the child did not point to one of the pictures, the researcher would repeat the sign and encourage the child to select one of the pictures (e.g., ‘‘You can guess.’’). A second researcher recorded the child’s response. During presentation of the practice signs, if the child correctly identified the target picture, she was told that she was correct (e.g., ‘‘That’s right!’’). If the child selected a drawing other than the target picture, she received positive feedback (e.g., ‘‘Good try, but.’’). In both cases, the researcher would then identify the correct picture by drawing attention to herself as she performed the sign, then pointing to the target picture (e.g., ‘‘See, this,’’ sign, ‘‘is this,’’ point to the picture). In addition, the researcher would place her hands over the target picture and perform

the sign directly over the drawing to emphasize the relationship between the sign and the target picture. All practice signs were presented even if the child appeared to immediately grasp the nature of the task. During the presentations of the test signs, the child was praised after each response (e.g. ‘‘Good job! You are good at this.’’) and received stickers after every 5 or 6 signs. No feedback was given as to the accuracy of the child’s response during the presentation of the test signs. Coding Transcripts were made from the videotapes of the 32 children who participated in the labeling condition. The children’s labels for the target pictures were coded whether they were correct (defined as using the predetermined correct label or its variant based on the sign, e.g., ball or baseball) or incorrect. Incorrect labels were further coded. In context labels identified a reasonable referent for the sign (e.g., snake instead of caterpillar). Mislabels either identified some aspect of the picture that was not related to the sign (e.g., boy instead of pizza) or completely misidentified the picture (e.g., truck instead of camera). The final two incorrect label codes included unintelligible and no response. Two graduate students were trained on the coding system. To establish and maintain intercoder agreement, 20% of the transcripts, randomly selected, were coded independently by both the graduate students. After every five transcripts coded, the students would compare their results on the transcript they both coded and resolve any disagreements. Across these transcripts, the coders agreed on 96% of the labels coded. Results We conducted two sets of analyses. The first addressed our research goals concerning the development of iconic representation. These include the effects of chronological age, language, and sign type on children’s ability to recognize iconic signs. The second set of analyses examined potential confounds to these results. We initially addressed our research goals as a whole by conducting a 3 (sign type) by 2 (labeling condition)

Spontaneous Recognition of Iconic Signs 231 Table 2 Percent correct on sign task by group and condition Condition Group

Label (SD)

n

No Label (SD)

n

Total (SD)

n

2.5 3.0 3.5 4.0 4.5/5.0 Total

36 46 54 67 83 55

7 8 6 6 5 32

37 47 50 59 77 53

7 7 9 5 6 34

36 46 52 64 76 54

14 15 15 11 11 66

(8) (12) (11) (9) (4) (18)

(12) (15) (13) (15) (12) (18)

(10)a (13)a,b (12)b,c (12)c (12) (18)

Note. Group total means that do not share subscripts differ at p 5 .05 in Tukey’s honestly significant difference post hoc comparisons. The Tukey Critical Difference was 12.6 (i.e., groups that differed by approximately 13% in their performance on the Sign Test were significantly different at the .05 level).

Developmental Progression There was a distinct developmental progression in the ability to perceive iconicity with the older children performing better than the younger children. Tukey’s honestly significant difference post hoc analysis revealed that the 2.5-year-old children recognized significantly fewer signs than all older children except the 3.0-year-olds (see Table 2). In addition, the children in the 4.5/5.0-age group were able to recognize more of the iconic signs than the children in any of the other groups. The ability of children in each age group to recognize iconic signs was further examined in two ways. First, using t-tests, group performance was compared to chance (i.e., 25% because there were four choices for each sign). All groups performed significantly above chance. Second, we assessed individual performance by comparing each child’s performance to chance. Based on the binomial distribution, in order for performance to be statistically above chance, a child had to correctly identify at least 13 (43%) of the signs.

Only two out of the 14 2.5-year-old children performed above chance, whereas more than half of the children in each of the other groups and all the children in the 4.5/5.0 group performed above chance (see Figure 2). The results of the individual analysis suggest that few 2.5-year-olds appreciate iconicity; however, given the number of signs, a binomial test is a rather stringent test. Language We assessed the relationship between language and sign task performance in three ways. First, we examined the relative effects of chronological and language age on performance using hierarchical multiple regression. We performed two analyses. In the first analysis, we entered chronological age first followed by language age (as measured by the PPVT). Chronological age accounted for 59% of the variance and language

Above Chance Chance

100%

Percent of Children

by 5 (age group) repeated measures analysis of variance (ANOVA). Sign type was a within-subject variable and labeling condition and age group were between subject variables. There were main effects of age, F(4, 56) 5 23.57, p 5 .000, and sign type, F(2, 112) 5 12.34, p 5 .000, but no effect of labeling condition. None of the interactions were significant. These main effects were examined in more detail through additional analyses reported below. Table 2 shows the performance by age group and labeling condition.

80% 60% 40% 20% 0%

2.5

3.0

3.5

4.0

4.5 - 5.0

Age Group

Figure 2 Percentage of children above chance. For individual performance, at least 43% (13 out of 30) correct on Sign Test is statistically above chance.

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Table 3 Effect of chronological and language age on sign task performance Model

R2

R2 change

F change

df1

df2

p

Chronological age Chronological 1 language age Language age Language 1 chronological age

0.59 0.65 0.43 0.65

0.59 0.06 0.43 0.21

91.48 10.11 48.52 38.03

1 1 1 1

64 63 64 63

.000 .002 .000 .000

age accounted for an additional 6% (see Table 3). In the second analysis, we entered language age first that accounted for 43% of the variance and chronological age accounted for an additional 21%. Based on these results, relative to language age, chronological age appears to be a stronger predictor of sign task performance in preschool-aged children. Next, we asked if children’s ability to recognize the signs was influenced by labeling the pictures used in the sign task. The initial ANOVA revealed that there was no effect of labeling condition (see above). In fact, as Table 2 shows, the performance was nearly (and surprisingly) identical between the children in the labeling and nonlabeling conditions with a difference of only 1% among the 2.5 and 3.0-year-old children. The labeling condition included trials when the child produced the correct label and trials when the researchers produced the label because the child did not. Because research suggests recognition of iconicity is influenced by the child’s production of labels, we examined this possibility specifically. We analyzed if children were more likely to identify a sign if they labeled the target picture correctly themselves. We used an odds ratio to analyze this relationship because unlike probability measures, odds ratios are not subject to some of the restrictions that may cause assumption violations or biases in para-

metric statistical analyses (Bakeman & Gottman, 1997; Rosner, 2000). The odds ratio for this analysis was calculated by dividing the odds of identifying the sign if the target picture was correctly labeled by the odds of identifying the sign if the target picture was not labeled correctly. In general, 2.5- and 3.0-year-old children were more likely to identify the sign if they labeled the picture (see Table 4). The odds of 2.5-year-olds identifying a sign if they labeled the target picture were almost four times the odds of them identifying the sign if they did not label the picture correctly. Children 4.0 years and older performed the same whether they labeled the picture correctly or not. ANOVA with the log-transformed odds ratio as the dependent variable and age group as the independent variable yielded nonsignificant results, F(4, 27) 5 1.179, p 5 .342. However, this result is probably due to the lack of power due to the small sample sizes (groups ranged from five to eight children in the labeling condition). The relationship between the odds ratio and chronological age, however, approached significance, r 5 2.325, p 5 .069. Sign Type The initial ANOVA revealed that there was a main effect of sign type but no interactions between sign

Table 4 Sign task performance by group and accuracy in labeling target picture Percent of signs correctly identified Age group (n)

Percent of pictures labeled correctly (SD)

Odds ratio

Picture labeled correctly

Picture labeled incorrectly

2.5 (7) 3.0 (8) 3.5 (6) 4.0 (6) 4.5/5.0 (5)

47 44 52 57 65

3.8 2.6 2.5 1.4 1.3

45 55 55 66 83

26 39 50 69 81

(4)a (13)a (12)a,b (11)a,b (9)b

Note. Groups that do not share the same subscript differ at p , .05 in the Tukey post hoc comparison. Odds ratio 5 [(correct label and recognized sign)/(correct label and did not recognize sign)]/[(incorrect label and recognized sign)/(incorrect label and did not recognize sign)]. Incorrectly labeled pictures include all types of mislabels (e.g., labeled part of picture not related to sign, no response) except for those coded as unintelligible.

Spontaneous Recognition of Iconic Signs 233

Mean Number Correct

9 8

4.5 - 5.0 4.0 3.5 3.0 2.5

7 6 5 4 3 2

Pantomime

Both

Perceptual

Sign Type

Figure 3 Group performance on different types of signs.

type and age group or between sign type and labeling condition (see above). Bonferroni-adjusted pairwise comparisons showed that children performed significantly better on pantomime (mean 58%) than on either perceptual (mean 48%) or both type signs (mean 47%). There was no difference in performance between signs depicting perceptual features and those depicting both perceptual and pantomimic aspects of the referents (Figure 3).2 The percentage of children who correctly identified each sign is shown in Appendix A. Secondary Analyses of Confounding Variables Developmental progression. The first set of analyses examined whether the age effects on sign task performance was due to the children’s familiarity with the referents rather than their ability to recognize iconicity. Although we did not test directly for familiarity, we considered children correctly labeling the referent picture as an indication of their familiarity with the referent. We first assessed the effect of age on how well the children were able to label the pictures. If the older children in this study could correctly label more target pictures than younger children, their better performance on the sign task may be due to the ability to use the target picture as a symbol as much as their ability to recognize the iconic gesture as one. Table 4 shows the percentage of target pictures correctly labeled by children in each age group. A one-way ANOVA revealed an age difference in the ability to label the target pictures, F(4, 27) 5 4.00, p 5 .01. Three-year-olds correctly labeled the lowest percentage of target pictures (44%), whereas the 4.5 and 5.0-

year-olds correctly labeled the highest percentage (65%). However, based on Tukey post hoc analysis, the four lowest age groups (2.5–4.0) did not differ from each other nor did the three oldest (3.5–5.0). Perhaps, even more important than the statistical analysis, 2.5-year-olds labeled more pictures correctly than 3.0-year-olds. Because the four youngest age groups were similar in their ability to label the pictures, the development of the ability to interpret the iconic signs is unlikely a function of their ability to identify the pictures. Another way of addressing the possible confound of familiarity is to examine performance on referents to which all children are likely to be equally familiar. Using labeling as an indication of familiarity, we identified three subsets of signs: those that were identified by all children in the labeling condition (house, eyeglasses); those labeled correctly by all 2.5-year-olds (house, eyeglasses, banana, window); and those labeled correctly by at least 70% of the 2.5-year-olds (house, eyeglasses, banana, window, telephone, bike, baby, tiger, mirror). As Table 5 shows, the pattern of results for each of these subsets was almost identical to that of the performance for all 30 signs. These numbers indicate that familiarity was unlikely a factor in the results. Sign type. This analysis addressed the potential confound between sign type (e.g., pantomime, perceptual, both) and referent type (e.g., noun, verb, adjective). Twenty-one of the referents were nouns (5 pantomime, 6 perceptual, and all 10 of both type Table 5 Percent of signs identified among subsets of signs selected according to familiarity with referent as indicated by labeling of target picture Sign set Age group

1

2

3

All signs

2.5 (14) 3.0 (15) 3.5 (15) 4.0 (15) 4.5/5.0 (11)

32 57 63 55 91

32 50 48 57 80

34 50 50 61 81

36 46 52 64 76

Note. The pictures for sign set 1 (HOUSE, EYEGLASSES) were labeled correctly by all children in the labeling condition; sign set 2 (HOUSE, EYEGLASSES, BANANA, WINDOW) by all 2.5-yearolds; sign set 3 (HOUSE, EYEGLASSES, BANANA, WINDOW, TELEPHONE, BIKE, BABY, TIGER, MIRROR) by at least 70% of the 2.5-year-olds.

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Table 6 Percent of pantomime signs correctly identified by referent type Age group (N)

Verbs

Nouns

2.5 (14) 3.0 (15) 3.5 (15) 4.0 (11) 4.5/5.0 (11) Total (66)

46 52 52 62 76 56

39 49 65 78 78 60

signs); seven of the referents were verbs (five pantomime and two perceptual); and two of the perceptual signs referred to adjectives. Because a higher proportion of pantomime signs referred to verbs than was the case for perceptual or both signs, the better performance on pantomime signs may have been because they depicted actions more than the other two types of signs. However, a repeated measures ANOVA among just the pantomime signs (five verbs and five nouns) showed neither an age by referent type interaction, F(4, 61) 5 1.29, p 5 .284 nor a main effect of referent type, F(1, 61) 5 1.16, p 5 .287 (see Table 6). This suggests that the effect of sign type was not due to referent type; however, this result should be treated with caution because it is unclear if the way in which we categorized the referent types was consistent with the children’s interpretations of the referents. Discussion Iconicity is not transparent, nor does appreciation for iconicity develop at any one time. Instead, significant developmental changes seem to occur throughout the preschool years. The development of the ability to derive meaning from iconic signs is continuous during these early years. The ability to spontaneously recognize the meaning of iconic signs is fragile by 2.5 years, relatively established by 3.5–4.0 years, and perhaps adult like by 4.5–5.0 years of age. The lack of insight into the relationship between iconic gestural symbols and their referents may be one reason why infants and toddlers do not exploit the possibilities that iconic gestures and signs offer. Although both deaf and hearing 1- to 2-year-olds easily acquire the conventionalized gestures and signs used by their parents, they rarely produce novel gestures and those that they do seem to be ‘‘abstracted’’

from motor routines (Namy et al. 2000). Indeed, even though deaf toddlers of deaf parents live in an environment that is rich in visual iconic gestures and signs they do not gesture more than hearing toddlers of hearing parents (Spencer, 1993). In addition, young native language learners may not show a preference for iconic over arbitrary signs because the meaning of many iconic signs is not transparent until sometime after 3 years of age. Older deaf children, on the other hand, exploit the iconic potential of gestures. Hearing and deaf preschoolers are able to communicate to each other without language using novel gestures, much as adults do in the game charades (Lederberg, Ryan, & Robbins, 1986). Research with older children also suggests that gestures that are pantomimic in origin are easier to acquire than those that represent features. Deaf preschoolers of hearing parents deprived of input create spontaneous novel iconic gestures (Goldin-Meadow, 2003). Descriptions of these ‘‘home-sign systems’’ suggest that early ‘‘characterizing’’ gestures function like action-like verbs in communication, whereas objects are more likely to be represented by points, even when children refer to absent objects. As these children develop, features become more represented in their systems. Deaf children acquiring ASL also acquire manipulative handler classifiers system by 3 years of age, whereas SASS classifiers are later developing (Schick, 2006). These results also offer practical advice for assessing deaf children’s sign vocabulary knowledge using receptive vocabulary tests such as CPVT or PPVT. Based on the ability of hearing elementary school children to accurately guess the meaning of many of the signs of the CPVT, White and Tischler (1999) expressed concerns that deaf children can do the same and, thus, be credited with knowing more words than they do. Our results suggest that by 4.5-years-old, children possess the ability to flexibly use iconicity to guess many of the signs used in the CPVT. Although even with younger children caution should be used in interpreting CPVT scores, the younger children’s low level of performance suggests iconicity will play less of a role in their performance on this test. Indeed, Moeller and Johnson (1988) found that deaf children do not obviously exploit iconicity on

Spontaneous Recognition of Iconic Signs 235

receptive vocabulary tests until early elementary school. This research can also contribute to understanding of development of the ability to attribute meaning to iconic symbols. Our results are consistent with other experimental research in that the way that 3-year-olds appreciate iconicity is different from 2.5-year-olds. At 3 years of age, children seem to become capable of directly deriving meaning from iconic symbols because of the visual relationship between the icon and its referent. In our study, the majority of 3-year-olds performed above chance in their ability to recognize novel iconic signs. Other research also has noted a developmental shift around 3 years of age in children’s ability to recognize iconic gestures that have not been previously modeled and to spontaneously derive meaning from iconic objects and pictures (Callaghan, 1999, 2000; Tomasello et al. 1999). This suggests that by 3 years, appreciation of iconicity may be more flexible and is not reliant on unique aspects of the mode of communication (e.g., the metonymic aspects of iconic gestures), nor is it inhibited by them (e.g., dual representation aspects of iconic objects). On the other hand, both our results and that of experimental studies across domains show that for 2.5-year-olds the ability to derive meaning from iconicity is largely dependent on context. When the dual representational aspects of iconic objects (i.e., as symbols and as objects to be manipulated) are mitigated (e.g., putting objects behind glass so they cannot be manipulated), 2.5-yearolds can act on the iconic aspects of the objects when they could not before the intervention (DeLoache, 1991, 2002). They can also recognize iconic gestures when those gestures are derived from actions performed in demonstrating objects just prior to a task (Striano et al. 2003). However, as our results indicate, when an iconic sign is ‘‘novel,’’ a 2.5-year-old has difficulty relating it to its referent. The literature suggests that whereas these types of contextual supports may improve the performance of older children, it is critical to the performance of children younger than 3 years. We have added to this literature by providing evidence that two of these supporting mechanisms are important in deriving meaning from iconic signs. First, being able to label the referent (i.e., picture) seemed to promote the ability to link the sign to the

picture. This is similar to Callaghan’s finding of the importance of labeling for young children’s ability to recognize iconic pictures (Callaghan, 2000). Interestingly, the researchers’ labeling of the pictures did not facilitate the children’s understanding of the gestures, and surprisingly, the children’s general vocabulary knowledge did not seem very important to the development of this ability. Children 2.5- and 3.0-years-old were most successful at interpreting iconic signs when they produced the pertinent label for the referent. This primary link (i.e., having the relevant aspect of the referent robustly represented in the mind) appears to be critical for 2.5-year-olds and important for 3.0year-olds but gradually less important throughout the later preschool years. This would also suggest young deaf children just learning language may be less able to appreciate the iconicity contained in signs than the hearing children tested in this study. On the other hand, language-delayed deaf children may be able to use iconicity to bootstrap their acquisition of signs. The second factor that influenced interpretation of iconic signs was the way in which the referents were represented by the signs. Across ages, signs that only depicted the action by or on the referent were easier than signs that included depiction of perceptual features of the referent. These results are consistent with observations of the gestures used by hearing toddlers (Acredolo & Goodwyn, 1988). Acredolo and Goodwyn noted ‘‘the results showed a clear preference for using an imitation of an action the child did with the object (45% of the total). An additional 13% of the total were imitations of actions inherent in the object, and 10% were depictions of some perceptual quality of the object’’ (p. 460). The influence of sign type had a longer developmental trajectory than that of verbal mediation. Whereas the effect of labeling declined by 3.5 years and was relatively unimportant by 4.0 years, the effect of sign type was evident throughout this period. The relative difficulty that young children seem to have identifying signs based primarily on perceptual features is particularly telling when compared to the performance of adults. For example, adults recognized the sign for HOUSE (hands shaped to represent the inverted V of a roof then sliding down to form the walls) 100% of the time, even when they were required to label the sign without the aid of pictures.

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Journal of Deaf Studies and Deaf Education 13:2 Spring 2008

Yet the preschool-aged children were notably less successful at identifying HOUSE especially when compared to their performance on the other signs. Out of the 30 signs tested on children, it ranked 18th (52%) in ease of identification in spite the fact that all children required to do so were able to label the house picture correctly. These results, though, should be treated with caution because we did not assess the relative complexity of the signs. In addition, the categorization of sign type is not straightforward as evidenced by the number of signs that were categorized differently by researchers and naive adults. Future research that constructs gestures that map to the same referent but differ on this dimension would provide more definitive answers to some of the questions raised by this aspect of our study. This would also address the potential confound between sign type and referent type present in this article. Spontaneously recognizing iconic signs is not easy. Even adults can have difficulty interpreting iconic signs, especially if they do not have cues like objects or pictures to prompt recognition. When we were developing the sign task for this study, we required some adults to produce labels for the signs (i.e., they did not have pictures from which to choose). Under these more difficult conditions, adults were able to label only seven signs over 80% of the time, and they were completely unable to label five others (see Appendix B). All these signs were easily recognized by adults when cued by pictures. It appears that interpretation of iconic signs is not automatic, and context is critical. One important difference between most iconic gestures and iconic symbols in other domains (e.g., objects and pictures) is the degree of iconicity. There are other differences, some of which may make the interpretation of iconic gestures easier for young children (e.g., lack of dual representation), and some of which may influence development in unique ways (e.g., the inherent motion in gestures). However, in spite of these differences, the ability to derive meaning from iconicity in gestures seems to manifest itself at approximately the same time as it does in other domains. The implication is that there are domain general processes that mature to such an extent that iconic representation becomes functional across symbol systems at about 3 years. These processes likely

include perceptual differentiation and categorization (Callaghan, Rochat, MacGillivray, & MacLellan, 2004) and analogical reasoning (Callaghan et al., 2004; DeLoache, 2002). Analogical reasoning, though, may be the ‘umbrella’ process that is key to deriving meaning from iconicity. In order to map a nonconventional iconic symbol onto a referent, an individual must appreciate structural similarities between the icon and referent in the absence of literal similarities (Gentner & Medina, 1998). For example, occasionally, the older children in our study would spontaneously talk out loud and describe how they were making the connection between the sign and the referent by making feature matches between the gesture and certain aspects of the picture. They seemed to recognize that the ‘‘rule’’ was that the picture that most closely matched the abstracted features depicted by the gesture was the one being represented by the symbol. Appreciation for this rule is important across domains. However, there may be domain differences in the way precursors to analogical reasoning scaffold the ability to appreciate iconicity. There is one characteristic of iconic gestures that makes them unique compared to other domains and possibly gives them an advantage for some types of analogical mapping. Iconic gestures inherently lend themselves to action-based representations. Although preschool-aged children may have some difficulty recognizing gestures based on static features of referents, matching gestures based on actions or motor routines seems to develop early. This is likely distinctive of iconic gestures and does not fit neatly into domaingeneral theories about iconic representation. This aspect of iconic gestures may tap a different representational system than those accessed by iconic pictures and objects. The more easily identified, purely pantomimic signs may have the effect of ‘‘exciting analogous sensations’’ in the mind as described by Peirce (1894) in the sense that they access some form of procedural or action-based memory that is relatively robust and in many cases not consciously represented. This hypothesis is consistent with research on motor neurons that shows that in monkeys these neurons are activated not only when objects are manipulated but also when similar gestures are observed (Rizzolatti & Arbib, 1998). It has been suggested that these neurons function as

Spontaneous Recognition of Iconic Signs 237

a mechanism for anticipating actions in conspecifics (Wilson & Knoblich, 2005). Action-based iconic gestures may be developmental precursors to language although not necessarily in the way suggested by Werner and Kaplan (1963). Early in the development of social communication, toddlers begin to extrapolate from motor or action routines. This extrapolation allows them to perform actions intended, although not completed, by adults (Meltzoff, 1995). This may be why children as young as 18 months will respond to iconic gestures that have not been explicitly modeled although demonstrated repeatedly through actions on target objects (Namy, 2005). Even children older than 2.5 years who begin to incorporate other processes in the interpretation of iconic gestures perform better when they can rely on the earlier developed, more stable processes that allow them to treat seemingly novel iconic gestures as metonyms, or signals for action schemas (Tomasello et al. 1999).

Appendix A

In conclusion, contrary to the beliefs of early psychologists, young hearing children do not find iconic symbols easy to interpret. There may be a major cognitive shift around 3 years of age that enables children to interpret the meaning of iconic gestures, pictures, and objects. Although there may be some mechanisms that are unique to each of these symbolic domains, many of the processes that enable appreciation for iconicity are the same across domains. For young deaf children learning sign language, it seems unlikely that the acquisition of iconic signs is influenced by appreciation for iconicity per se. However, for deaf children older than 3 years, bringing attention to the iconic aspects of some signs may enhance language development. Future research needs to develop models of the interaction of the mechanisms within and across symbol domains, as well as examine developmental changes in the influence of iconicity in sign language development.

Percent of children who correctly identified each sign Age group (n)

Sign (type)

2.5 (14)

3.0 (15)

3.5 (15)

4.0 (11)

4.5–5.0 (11)

All (66)

ICE CREAM (B) BABY (Pn) MIX (Pn) EAT (Pn) CATERPILLAR (B) SHOWER (Pr) BIKE (B) RING (B) SMOOTH (Pr) HAMMER (Pn) TIGER (Pr) CAMERA (B) PERFUME (Pn) WINDOW (B) HOUSE (Pr) BASEBALL (Pn) LOOK (Pr) WRITE (Pn) GLASSES (Pr) TORNADO (Pr) TOWEL (Pn) BANANA (B) MIRROR (B) TISSUE (Pn)

64 64 64 64 57 50 50 50 50 43 43 43 43 43 36 36 36 36 29 29 29 21 21 21

80 67 60 60 47 67 60 47 33 87 53 47 47 27 60 53 33 13 53 47 33 60 47 47

87 73 73 53 93 67 60 27 67 73 47 73 73 13 53 67 33 53 73 27 60 53 60 53

82 73 73 73 73 73 100 36 82 91 36 91 82 45 27 91 64 45 82 91 73 73 64 73

100 73 64 91 91 91 82 91 82 100 91 100 82 55 82 91 73 73 100 91 73 82 73 73

82 70 67 67 71 68 68 48 61 77 53 68 64 35 52 65 45 42 65 53 52 56 52 52

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Appendix A

Continued Age group (n)

Sign (type)

2.5 (14)

3.0 (15)

3.5 (15)

SEWING (Pn) GLOBE (Pr) NARROW (Pr) NEEDLE (B) TELEPHONE (B) VASE (Pr)

21 21 14 14 0 0

40 20 40 20 20 7

7 27 40 27 13 27

4.0 (11)

4.5–5.0 (11)

27 36 36 45 45 27

55 45 73 82 91 45

All (66) 29 29 39 35 30 20

Note. Pn, pantomime; Pr, perceptual; B, both. Signs are listed based on the performance of 2.5-year-olds. The shaded cells indicate the selected target picture at greater than chance levels.

Appendix B Pantomime only signs

Percentage of adults who identified each sign without picture cue Percent identified

Perceptual only signs

Percent identified

Pantomime and perceptual signs

Percent identified

100 100 68 35 21 19 15 0 0 0

TELEPHONE RING BIKE ICE CREAM BANANA CAMERA MIRRORa WINDOW CATERPILLAR NEEDLE

100 90 55 45 40 32 25 25 21 15

Test signs BABY PERFUME EAT SEWING WRITE MIX HAMMER TISSUE BASEBALL TOWELa

90 89 84 74 65 28 15 11 0 0

HOUSE LOOK SMOOTH GLASSES TORNADOa NARROW SHOWER VASE TIGERa GLOBE

Practice signs a

HAT COLD

15 11

a

BOX BALL

45 20

BOOK JARa

20 3

a

Based on two samples of 20 adults each, all other signs tested on one sample of 20 adults.

Notes 1. A more detailed report of these studies is available from the first author. 2. Classification into sign type was done by consensus among the researchers. We also asked 73 college students to code the signs as depicting action (either by a person or by an object), depicting a feature or shape of an object, both, or neither. To make the situation analogous to the children’s task, the adults were given the picture of the sign but not told the meaning of the sign. The adults’ categorizations were used to determine which signs clearly depict the three categories. Repeated measures ANOVA of children’s performance on two subsets of signs continued to show that pantomimic signs were easier to recognize than perceptual ones. For the first subset, 18 signs (seven pantomime, six both, five perceptual) were categorized the same way by the researchers and by a majority of participants. There was only a main effect of sign type, F(2, 122) 5 35.35, p 5 .000. Performance was significantly higher

on pantomime signs (mean 64% correct) than on either both (mean 40% correct) or perceptual signs (mean 41% correct). The second analysis included 10 signs for which at least 70% of adults agreed on their categorization: pantomime (eat, tissue, towel), perceptual (globe, house, vase), and both (camera, banana, telephone, caterpillar). There was again only a significant main effect of sign type, F(2, 122) 5 17.79, p 5 .000. Performance on pantomime (mean 57% correct) and both signs (mean 56% correct) was the same and significantly higher than performance on perceptual signs (mean 33% correct).

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