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Although gestural communication is largely visuospatial, the extent to which a visual model is necessary for the development of gesture is unclear. This chapter summarizes recent research on gesture production by congenitally blind speakers and discusses the implications of these results for the hypothesized link between gesture and thought. Gesture When There Is No Visual Model Jana M. Iverson Gesture and speech are semantically coexpressive; words and gestures typically cover the same referent but from different perspectives (McNeill, 1992; Chap- ter One). As a result gesture often contains information that is not explicit in speech. Produced without gesture, the sentence "I carried the box" is neutral with regard to features of the box such as size and weight. Produced with the speakers arms extended to the side and slightly bent, however, the same sen- tence tells the listener that the box was large and heavy. Gesture, in other words, can substantially influence the message that the listener abstracts from the communicative act (Goldin-Meadow, Wein, and Chang, 1992; McNeill, Cassell, and McCullough, 1994). Of course, such coexpression depends on the fact that gestural and spo- ken communication rely on different expressive modalities. Whereas spoken communication is primarily acoustic, gestural communication is largely visu- ospatial. In the preceding example, information concerning the size and weight of the box is carried by the relative extension of the speakers arms and the spa- tial and temporal aspects of the speakers movement. Gesture supplements the message by providing visuospatial information that is not included in speech. The fact that gestural communication is visuospatial in nature raises an interesting set of questions. To what extent is visuogestural input related to This research was supported by a National Science Foundation Graduate Fellowship, an American Association of University Women Dissertation Fellowship, and a grant from the March of Dimes (12FY96-0481). Special thanks to Robert Wozniak for his helpful com- ments on previous versions of this chapter. New DIRECTIONS FOR CHILD DEVELOPMENT, no. 79, Spring 1998 O Jouey-Bus Publisher* 89

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Page 1: Gesture when there is no visual model

Although gestural communication is largely visuospatial, the extent to which a visual model is necessary for the development of gesture is unclear. This chapter summarizes recent research on gesture production by congenitally blind speakers and discusses the implications of these results for the hypothesized link between gesture and thought.

Gesture When There Is No Visual Model Jana M. Iverson

Gesture and speech are semantically coexpressive; words and gestures typically cover the same referent but from different perspectives (McNeill, 1992; Chap­ter One). As a result gesture often contains information that is not explicit in speech. Produced without gesture, the sentence "I carried the box" is neutral with regard to features of the box such as size and weight. Produced with the speakers arms extended to the side and slightly bent, however, the same sen­tence tells the listener that the box was large and heavy. Gesture, in other words, can substantially influence the message that the listener abstracts from the communicative act (Goldin-Meadow, Wein, and Chang, 1992; McNeill, Cassell, and McCullough, 1994).

Of course, such coexpression depends on the fact that gestural and spo­ken communication rely on different expressive modalities. Whereas spoken communication is primarily acoustic, gestural communication is largely visu­ospatial. In the preceding example, information concerning the size and weight of the box is carried by the relative extension of the speakers arms and the spa­tial and temporal aspects of the speakers movement. Gesture supplements the message by providing visuospatial information that is not included in speech.

The fact that gestural communication is visuospatial in nature raises an interesting set of questions. To what extent is visuogestural input related to

This research was supported by a National Science Foundation Graduate Fellowship, an American Association of University W o m e n Dissertation Fellowship, and a grant from the March of Dimes ( 1 2 F Y 9 6 - 0 4 8 1 ) . Special thanks to Robert Wozniak for his helpful com­ments on previous versions of this chapter.

New DIRECTIONS FOR CHILD DEVELOPMENT, no. 79, Spring 1998 O Jouey-Bus Publisher* 89

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90 NATURE AND FUNCTIONS OF GESTURE IN CHILDREN'S COMMUNICATION

gesturemyduction? To what extent is the experience of seeing others gesture necessaryto the development of specific gestural movements? One way to address this question is to examine the relationship between parental gestures and gesture development in young sighted children (see Iverson, Capirci, Longobardi, and Caselli, 1997). A second way to assess the role of visuoges-tural input in gesture production is through the study of gesture in individu­als who are congenitally blind. Do people who have never seen the gestures of others gesture themselves? If blind speakers do gesture, do they make use of gesture to convey the same kinds of information as is conveyed by the gestures of sighted persons? Are the gestures of blind individuals idiosyncratic in form, or are they similar to those produced by sighted individuals? Do individuals who are congenitally blind gesture under the same conditions and in the same contexts as those who are sighted?

Surprisingly little research has examined the effect of blindness on ges­ticulation. In a pioneering study Blass, Freedman, and Steingart (1974) asked congenitally blind and sighted college students to give a five-minute mono­logue about an event of personal significance. They noted an almost total absence of gesture ("object-focused movement") among the blind subjects. Analyzing the nonverbal behaviors of congenitally blind adults engaged in con­versation, Manly (1980) found evidence of body-focused movements (for example, adjustments to hair, touching the face) and changes in posture sig­naling the end of conversational turns, but gesture was almost totally absent. This was true even when subjects produced adjectives of shape and size such as "short," "round," and "four inches long." Observing congenitally blind chil­dren during conversation, Parke, Shallcross, and Anderson (1980) found evi­dence of appropriate use of head nodding, but this movement was observed at a much less extensive set of conversational points than in sighted children. And in a study of blind preschoolers conversing informally with an experi­menter, McGinnis (1981) reported that the children made very little use of communicative gestures compared to their sighted age-mates.

These results have been interpreted as indicating that the relationship between vision and gesture is direct. Since individuals without visual access to the gestures of others make limited use of gestures themselves, vision must be a necessary precondition for the emergence of gesture. There is an alternative explanation for these findings, however. All of the research described thus far has focused on gesture production in a single context, that of relatively unstructured conversation (whether a dialogue or a monologue). Given the fact that some contexts fail to elicit gesture even in sighted speakers (Iverson and Goldin-Meadow, 1997), it is possible that congenitally blind subjects may be found to gesture under other circumstances. Before concluding that com­municative gesture depends on visual experience, further work is needed to examine blind speakers' gesture production in task contexts that are known to elicit gesture in sighted persons.

The purpose of this chapter is to review recent work that has focused on the evaluation of the relationship between variation in visual experience, task

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GESTURE WHEN THERE IS NO VISUAL MODEL 91

context, and gesture production in children and adolescents. In describing this research I will focus on three major questions:

1. Do congenitally blind children and adolescents gesture when speaking? 2. What kinds of information do blind individuals convey with their ges­

tures, and what form do these gestures take? 3. How does task context affect use of gesture in blind children and ado­

lescents?

Exploring Gesture in Congenitally Blind Speakers

In the work to be described here, the incidence, content, and form of gestures were observed in blind and sighted children and adolescents as they partici­pated in two tasks differing from each other and from the informal conversa­tion tasks employed in previous research. In a spatial description (route directions) task, children were asked to describe the route from a fixed start­ing location (usually a classroom or locker) to a set of familiar locations in their school building, locations to which they traveled on a regular basis (for example, the library, the cafeteria, the gym). In a reasoning (Piagetian conservation) task, participants were asked to reason about invariance across transformation in the context of making judgments about liquid quantity, length, number, and mass.

These tasks were selected for two reasons. First, sighted adults and chil­dren gesture extensively when performing such tasks (for example, see Church and Goldin-Meadow, 1986; McCullough, 1995). Second, spatial description and reasoning place different cognitive demands on the speaker. The spatial description task requires the speaker to convey information about paths and locations and to keep track of shifting points of reference in the space being described. In the reasoning task, participants beliefs about aspects of physical objects (for example, quantity, length, numerosity) are challenged, and they are asked to consider these objects in novel ways, to draw a set of logical infer­ences, and to generate explanations for these inferences.

Two groups were asked to engage in these tasks. The children and ado­lescents in the blind group had all been blind since birth, with at best minimal light perception; had no other known cognitive, emotional, or behavioral impairments; and were between the ages of eight and eighteen years. The chil­dren and adolescents in the sighted group had full vision; were similarly free of cognitive, emotional, or behavioral impairments; and were matched to the blind participants on the basis of age and gender.

Blind Speakers Do Gesture. In this section I describe the findings on gesture production by blind and sighted children and adolescents in the route directions and conservation tasks. Before presenting these findings, however, I briefly discuss data on speech production to situate the results on gesture pro­duction within the overall context of communicative production.

Speech Production. Overall speech production in the route directions and conservation tasks was assessed by totaling the number of words (excluding

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9 2 NATURE AND FUNCTIONS OF GESTURE IN CHILDREN'S COMMUNICATION

filled pauses such as "urn" and "uh") contained in each participant's response. In studies with two different samples (Iverson, 1 9 9 6 ; Iverson and Goldin-Meadow, 1 9 9 7 ) we found that blind children and adolescents produced sig­nificantly greater amounts of speech in the route directions task than did their sighted peers. (This effect was also noted for conservation tasks in the 1 9 9 7 report.) The finding of increased speech production in congenitally blind indi­viduals is consistent with research indicating more efficient use of verbal mem­ory in blind children compared to their sighted peers (Dekker and Koole, 1 9 9 2 ) . That blind children might make greater use of language to code and retrieve information is not surprising in light of their inability to make use of the visual cues that are so often redundant with verbal information.

Gesture Production. Overall gesture production was analyzed in much the same way as was speech production—that is, by calculating the number of ges­tures contained in each participant's response for each task. This analysis revealed a striking group-by-task interaction. In both of our samples the blind participants produced significantly fewer gestures than their sighted peers, but only in the directions task. In the conservation task both blind and sighted speakers gestured, and with similar frequency (Iverson, 1 9 9 6 ; Iverson and Goldin-Meadow, 1 9 9 7 ) . In certain contexts, then, congenitally blind children and adolescents definitely do gesture.

Although discussion of possible reasons for the difference between the groups in gesture frequency on the route directions task is taken up later in the chapter, one preliminary analysis, performed to rule out an obvious explana­tion, should be mentioned here. The fact that compared to their sighted peers blind participants gesture less and speak more in giving route directions raises the obvious possibility of a gesture-speech trade-off. Failing to gesture and rely­ing on speech as their sole mode of communication, do blind children and adolescents increase their volubility to compensate for the absence of gesture?

To assess this possibility we examined the patterns of speech and gesture production of individual participants. Dividing the blind group at the median for speech production, we looked to see whether there was any association between volubility (high, low) and status as a gesturer or nongesturer ( 6 7 per­cent of blind participants produced no gestures, and 33 percent produced some gestures when giving route directions). The results of this analysis indi­cated no apparent relationship between volubility on the directions task and status as a nongesturer. (Similar distributions were obtained for the sighted subjects: participants who did not gesture were no more likely to produce rel­atively large amounts of speech than were participants who did gesture.) What­ever the source of reduced gesticulation in the blind participants in the route directions task, it was not a simple function of increased volubility.

Blind Speakers' Gestures Look Like Those of Sighted Speakers. Given that blind children and adolescents do accompany speech with sponta­neous gestures under certain circumstances, the next question to be addressed is whether and to what extent their gestures resemble those of their sighted peers. To answer this question we further analyzed the participants' gestures

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in two ways. First, the content of each gesture was coded, and the data for the blind and sighted participants were compared to determine whether their ges­tures conveyed similar kinds of information. Second, the form (handshape and motion) of each gesture was noted, and the distribution of gesture forms for the blind and sighted participants was compared to assess whether the blind children and adolescents produced any gesture forms that were not in the repertoire of their sighted peers. Because gesturing in the blind children was relatively infrequent for the route directions task, the following analyses are restricted to data from the conservation task.

Information Conveyed. The gestures produced in the conservation task were classified according to their informational content, on the basis of the child's overall level of reasoning in the task (that is, reference to only one object, reference to the similarity or difference between two objects) and the type of evidence provided in support of this reasoning (Church and Goldin-Meadow, 1986). In one of our two studies (Iverson, 1996) both conservers and partial conservers were represented in the sample. In the other study (Iverson and Goldin-Meadow, 1997) the sample consisted almost entirely of full conservers.

For both conservers and partial conservers, the informational content in the gestures of blind and sighted children and adolescents was remarkably sim­ilar. In the later study (Iverson and Goldin-Meadow, 1997), the most commonly produced gestures in both groups were simple object indications (for example, pointing to the tall container of water). These accounted for 47 and 41 percent of all the gestures produced by the blind and sighted children, respectively. Ges­tures that focused on one of the dimensions of an object (for example, placing a flat hand on the top of one of the glasses of water to indicate its height) were the next most frequent (32 percent of the total for the blind group versus 29 percent for the sighted group). The incidence of all other specific gesture types was low but was generally comparable for the blind and sighted participants.

Gesture Forms. All gestures produced in the conservation task were fur­ther described in terms of the shape of the moving hand and the trajectory of hand motion. Handshapes were coded according to a system designed for describing hand forms in American Sign Language (Wilbur, 1987) , and motions were described in terms of the path, direction, and shape of the movement observed (for example, no motion, up-down motion, arced motion). In both samples the overall set of handshapes produced by the blind children and adolescents was similar to that used by their sighted peers, and no handshape was ever used by a blind child that was not also observed among the sighted children.

Handshape distributions varied by group, however. The majority of the handshapes produced by the sighted children and adolescents were points, generally touching or placed very close to the task objects. Among blind par­ticipants, however, points were extremely rare. Most of the handshapes employed by the blind children followed the natural configuration of the relaxed hand. These consisted primarily of a flat hand with fingers spread (a "5" hand), occasionally with fingers together ("B" or "B-spread" hand) or with all fingers bent in a C-like shape (a "C" hand).

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94 NATURE AND FUNCTIONS OF GESTURE IN CHILDREN'S COMMUNICATION

Why is the pointing handshape so rarely used by blind children? Before addressing this question it is important to note that although blind children did not typically point, they did use gestures (usually with their hands flat) to indicate or call attention manually to specific objects in their environment. Rel­ative absence of pointing in the blind participants was associated with increased use of flat-hand indicators. One way to interpret this trade-off is in terms of the relative function of pointing and flat-hand indication. When sighted individu­als point they establish a "visual line of regard" extending from the pointers eyes along the length of the arm and extended finger toward the referent of the point. When the intended referent is at a distance from the body, pointing local­izes it with considerable precision. For blind individuals, who cannot use vision to set up a line between the eyes, the index finger, and the gestural referent in distant space, indication tends to be restricted to near space—and in near space, objects can be indicated quite accurately with a flat hand.

With respect to hand motion, the results were generally similar to those obtained for handshape. The gestures of the blind children and adolescents incorporated the same kinds of motions as those produced by their sighted peers, but distributions of the frequency of motion types varied by group. While the vast majority of the sighted participants' gestures contained no motion (that is, were simply held near the object to which they referred), the blind children and adolescents made frequent use in gesturing of a tapping motion. The blind participants, in other words, tended to add an auditory cue to their gestures by tapping or patting the referent of the gesture; this addi­tional cue may have functioned to ensure that the experimenter and the blind participant were attending to the same object or object dimension.

Blind Speakers Don't Always Gesture. The data described thus far indi­cate that blind children gesture when reasoning in conservation tasks, that they produce approximately the same number of gestures as sighted children, and that the form and content of their gestures are remarkably similar to those of their sighted peers. I now turn to the data from the route directions task, in which the sighted children gestured extensively but the blind children gestured rarely, if at all. Why might this have been the case?

Before considering a possible explanation for this difference, it is worth pointing out that the blind children's failure to gesture in the route directions task was not simply a reflection of poor performance on the task. On the contrary, the blind children's directions were quite accurate, and as a group they conveyed as much path-related information as did the sighted children. Why, then, did the blind children make such litde use of gesture in conveying this information?

To address this question we examined the content of the blind and sighted children's speech more closely. Our reasoning was that if gesture and speech form a single system of communication based on a common cognitive repre­sentation, as has been argued by McNeill (1992; Chapter One), the striking group difference in gesture use on the route directions task might well be asso­ciated with a group difference in speech.

The results of our analysis yielded one highly salient difference between the speech of the blind and the sighted participants; this difference was in the

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use of landmarks. A landmark was defined as an object (for example, a water fountain or bulletin board) or location (for example, the cafeteria, the main office, the copy room) whose mention was not an essential part of the route being described. While the sighted children and adolescents made only mod­erate use of landmarks in giving route directions, the blind children and ado­lescents used landmarks with great consistency. In one of our samples the blind participants mentioned more than five times as many landmarks on average as did their sighted peers (sixteen versus three, respectively; Iverson and Goldin-Meadow, 1997); in the second sample the blind participants mentioned twice as many landmarks on average as did those who were sighted (eighteen ver­sus nine, respectively; Iverson, 1996).

In addition to the difference in the overall number of landmarks men­tioned, the blind and sighted children and adolescents also tended to make use of landmarks in different ways. The sighted children almost always employed landmarks to locate a place or a turn in the route. Thus, for example, when indicating the path from classroom to bathroom, one sighted child said, "Okay, there's one straight down there, and when you get near the staircase you turn to the left, except it's a little bit before the staircase."

Although the blind children also made use of landmarks in this fash­ion, they were much more likely to employ landmarks to break up a path into a series of small steps that were easily navigable from a blind person's point of view. To describe the path from the classroom to the gym, for exam­ple, one blind child mentioned a series of landmarks that divided the path into a progression of locations: "Turn left, walk north, then you'll see the office, then you'll see room 106, then 108, then 110, 112, then there's a doorway. Then there's a hall. You walk past the hallway. Then there'll be a girls' bathroom. And then it's [the gym) going to be on the right." Here the path is described in terms of a series of segments punctuated by landmarks, with each landmark indicating an intermediate step along the path. In other words, where sighted participants tended to describe a path as a global whole, blind participants used landmarks to break the path into a progres­sion of locations (see Brambring, 1982, for similar findings from work with blind adults).

Given this sharp group difference in speech, we next looked for a rela­tionship between blind and sighted speakers' preferred approaches to path description and their respective use of gesture. Specifically, we wondered whether the sighted participants' tendency to portray paths as a global whole might lend itself to gesture in a way that the blind participants' tendency to describe paths as a progression of segments might not.

This notion follows directly from McNeill's claim (1992; Chapter One) that gesture is by nature global and holistic, capturing multiple aspects of a scene simultaneously and conveying "the big picture." Viewed from this per­spective, gesture is well suited to conveying information about a path envisioned as a global whole. It may be less appropriate, however, for representing a path envisioned as a series of locations. One possible explanation for the observed group difference in gesture production during route directions, therefore, might

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96 NATURE AND FUNCTIONS OF GESTURE IN CHILDREN'S COMMUNICATION

be that the global representation underlying sighted persons' directions may be channeled into both speech and gesture, whereas the segmented represen­tation underlying blind persons' directions, not easily captured in gesture, may be channeled almost exclusively into speech.

Before examining this hypothesis it is important to note that the notion of global versus segmented path representations does not imply that blind and sighted individuals differ in their general ability to represent space (though this is a claim made by others; see Hartlage, 1969; Rieser, Lockman, and Pick, 1980) or that blind persons' tendency to construe paths as a series of segments represents a less advanced level of spatial understanding. My point is simply that the source of the striking group differences in gesture production may lie in qualitative differences in the way in which blind and sighted children and adolescents think about a path when they are asked to describe it to another person (see Millar, 1994, for further discussion of this issue).

If this is the case then we can make two further predictions. First, we would expect that when sighted children and adolescents verbally describe a path as a series of locations (suggesting that they have represented that path in a segmented fashion, as a blind person might), they should be less likely to produce gestures compared to other sighted children and adolescents who do not describe paths in a segmented manner. Although most of the sighted par­ticipants in these studies described paths as global wholes, some did at times verbally describe paths as a series of segments, and as predicted, these partic­ipants produced less than half as many gestures overall as peers who described paths only in terms of global wholes. Indeed, on those trials in which sighted children described a path as a series of segments, their verbal descriptions were never accompanied by gestures.

Second, we might also expect that on the relatively rare occasions when blind children and adolescents do gesture, their gestures should accompany paths described in speech as global wholes. Although very few blind partici­pants produced gestures in the directions task, the vast majority of the gestures that were produced by blind participants in this task (84 percent in the first study and 97.5 percent in the second study) accompanied spoken descriptions that portrayed the path as a global whole, without segmenting landmarks.

In short, differences in gesture production between the blind and sighted children and adolescents in the directions task appear to be linked to differ­ences in their speech content. Whereas the sighted children and adolescents tended to describe paths as global wholes, their blind peers tended to make use of a segmenting strategy in which the paths were divided into a series of smaller units punctuated by landmarks. The reduced use of gesture among the blind individuals in this task seems to be the result of a fundamental incom­patibility between their segmenting strategy and expression in the gestural modality. Apparently, then, it is the nature of the representation underlying communication, rather than the speaker's status as blind or sighted per se, that determines whether or not gesture will accompany speech in the route direc­tions task.

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Conclusions

Previous research on the use of gesture by congenitally blind speakers has reported a virtual absence of gesture production in the informal conversations of blind children and adults. Based on these findings, some investigators (for example, Manly, 1980; McGinnis, 1981) have argued that vision is a necessary precondition for the emergence of gesture. The studies described in this chap­ter, however, suggest that the relationship between gesture and lack of expo­sure to visuogestural input is more complex than was previously thought. With respect to the three major questions posed at the beginning of this chapter, these studies have revealed that not only do congenitally blind children and adolescents gesture, their gestures generally convey the same information and make use of the same forms as those of their sighted counterparts, and the nature of the task and the way in which the speaker (blind or sighted) appears to represent task-related information strongly influence the extent to which gesture is produced in that task.

Perhaps the most striking finding in this research is that children and ado­lescents who are blind from birth do gesture when speaking. This result is even more remarkable when we consider that blind speakers gesture even though they have no firsthand experience watching others gesture in communicative interactions and they may not even know that gesture can convey substantive information to a listener. At the same time, however, it raises two interesting questions. Are blind children aware that other people gesture? And why do they themselves gesture?

While the question of blind children's awareness of others' gestures is beyond the scope of the research described in this chapter, information gleaned informally during after-session discussions with the blind participants and their teachers sheds some light on this issue. The blind children and adolescents reported hearing and feeling the gestural movements of others (for example, "1 hear the rubbing of clothes" and "I feel the movement of the breeze"). They also reported receiving some information from their parents and teachers about the appropriateness of their own movements. For most blind individuals this process takes place informally, although blind students who take classes in public speaking or acting may actually receive direct coaching in gesture form and timing.

Although blind speakers can, therefore, learn something about the use of gesture from their own sensory experiences and from explicit instruction, the information they obtain from these sources is minimal at best. Unlike sighted children, they have no visuogestural models available for learning, and because they cannot see their listeners, whatever feedback they receive on their own gesture production is markedly reduced. Why, then, do blind speakers ges­ture? If learning cannot account for blind children's acquisition of gesture, what does drive gesture production in blind speakers?

One possibility is that blind speakers gesture because movement is a nat­ural accompaniment to speech (for example, see Blass, Freedman, and Steingart,

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9 8 NATURE AND FUNCTIONS OF GESTURE IN CHILDREN'S COMMUNICATION

1 9 7 4 ; Freedman, 1 9 7 2 ; Freedman and Hoffman, 1 9 6 7 ; Tuite, 1 9 9 3 ) . Although the particular form that such movement takes may depend on the history of the individual and the task context, the presumption here is that people are naturally predisposed to move when speaking and that, under appropriate cir­cumstances, such movement will be translated into gesture. Although we do not yet know what these circumstances are or whether the gestures that accom­pany speech play an active role in thought construction or serve merely as an index of underlying cognitive process (a topic to which I will return), this view is nevertheless consistent with the emergence of gesture in those who have had no exposure to visuogestural input.

The second major finding of the studies described here is that when the blind children and adolescents gestured, their gestures closely resembled those of their sighted counterparts. Thus in the conservation task the blind partici­pants' gestures conveyed the same types of information as those of their sighted peers, focusing on only one object and either indicating that object or high­lighting one of its attributes (for example, height, length, width). This simi­larity is quite striking in light of the fact that the blind and sighted children gathered information about the task objects using different sensory modalities: the blind children explored the objects haptically, whereas the sighted children explored them visually. As Kennedy ( 1 9 9 3 ) has suggested, spatial properties of surfaces (for example, the corners and edges of objects) may be as accessi­ble to touch as they are to vision. Object exploration, in other words, may involve cross-modally invariant cues that are equally accessible to both blind and sighted individuals. Similarities in gesture content across the blind and sighted groups on the conservation task may thus reflect commonalities in their underlying representations of the task.

In addition to these observed similarities in gesture content, there were also similarities in the gesture forms employed in the conservation task. No handshape or motion was used by a blind participant that was not also observed among the sighted subjects. Although at first glance this may seem puzzling, given the fact that the blind subjects had had no access to visual models of handshapes and motions, the absence of atypical gestures among the blind participants may simply be a function of constraints on form and movement introduced by the anatomical and biomechanical properties of hands and arms. In other words, the blind participants' handshapes and motions fit within the range observed among the sighted participants simply because there are a relatively limited number of ways in which the hand and arm can be configured and moved.

Finally, gesture production was found to vary widely among the blind and sighted participants as a function of task context. Whereas the sighted children produced a relatively large number of gestures in both the directions and conservation tasks, the blind children gestured extensively only in the conservation task. In a previous section I outlined a possible explanation for the absence of gesture in the blind group on the directions task; here I focus

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on why the conservation task may have elicited gesture so reliably in the blind and sighted subjects. There are at least two possible explanations for this effect.

One way to account for gesture elicitation during the conservation task might be in terms of the presence of task objects during the participants' responses. Most of the gestures produced in the conservation task involved indicating aspects of task objects that had just been manually or visually explored. The continued presence of concrete, previously explored referents may have supported gesture production by making salient physical aspects of the task accessible for ready reference during explanation. To date this possi­bility has not been experimentally tested, but it seems somewhat unlikely in light of the finding that both blind and sighted children and adolescents read­ily produce gestures in other task contexts (for example, description of a small-scale spatial layout) in which previously explored objects are not physically present during the response phase (Iverson, 1996).

A second possible explanation for the blind participants' gesture produc­tion during the conservation may be related to the fact that conservation tasks involve a form of logical reasoning that was not tapped by the directions task. Conservation explanation asks children to examine the assumptions on which their beliefs about quantity are based. Up until the moment that the question is asked, these beliefs are likely to have been unexamined and unquestioned by the child, and they are therefore relatively difficult to put into words. It seems possible that gesture may help a child think through the problem by providing a medium for expressing relatively inarticulable thoughts. Gesture in the conservation task, in other words, may be a natural accompaniment to thought, produced more for the speaker than for the listener.

In sum, the studies just reviewed indicate that congenitally blind children and adolescents can and do gesture, and more generally that visual experience is not essential to gesture development. Moreover, despite their lack of visual experience with the gestures of others, blind participants produce gestures that resemble those used by sighted children and adolescents. They do so, how­ever, only in the context of reasoning provided by the conservation task. When asked to give route directions, gesture use by blind participants is sharply restricted.

This pattern of results contributes to our understanding of the relation­ship between gesture, vision, and thought in two important ways. On the one hand the findings clearly support the claim that gesture and thought are inti­mately linked (McNeill, 1992; Chapter One). On the other hand they suggest that visual experience plays an important role in determining the extent to which gesture will be employed in a given context. While future work is needed to investigate the many factors that affect gesture production and to assess the possible cognitive functions of gesture, findings from this research suggest that the tight link between gesture and thought remains intact even when visual input is absent.

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JANA M. IVERSON is a postdoctoral fellow in the department of psychology, Indiana University