Hand matters: Left-hand gestures enhance metaphor explanation

Intact speech-gesture integration in narrative recall by adults with moderate-severe traumatic brain injury

PURPOSE

Real-world communication is situated in rich multimodal contexts, containing speech and gesture. Speakers often convey unique information in gesture that is not present in the speech signal (e.g., saying "He searched for a new recipe" while making a typing gesture). We examine the narrative retellings of participants with and without moderate-severe traumatic brain injury across three timepoints over two online Zoom sessions to investigate whether people with TBI can integrate information from co-occurring speech and gesture and if information from gesture persists across delays.

METHODS

60 participants with TBI and 60 non-injured peers watched videos of a narrator telling four short stories. On key details, the narrator produced complementary gestures that conveyed unique information. Participants retold the stories at three timepoints: immediately after, 20-min later, and one-week later. We examined the words participants used when retelling these key details, coding them as a Speech Match (e.g., "He searched for a new recipe"), a Gesture Match (e.g., "He searched for a new recipe online), or Other ("He looked for a new recipe"). We also examined whether participants produced representative gestures themselves when retelling these details.

RESULTS

Despite recalling fewer story details, participants with TBI were as likely as non-injured peers to report information from gesture in their narrative retellings. All participants were more likely to report information from gesture and produce representative gestures themselves one-week later compared to immediately after hearing the story.

CONCLUSION

We demonstrated that speech-gesture integration is intact after TBI in narrative retellings. This finding has exciting implications for the utility of gesture to support comprehension and memory after TBI and expands our understanding of naturalistic multimodal language processing in this population.

Production of co-speech gestures in the right hemisphere: Evidence from individuals with complete or anterior callosotomy

INTRODUCTION

A right-hand preference for co-speech gestures in right-handed neurotypical individuals as well as the co-occurrence of speech and gesture has induced neuropsychological research to primarily target the left hemisphere when investigating co-speech gesture production. However, the substantial number of spontaneous left-hand gestures in right-handed individuals has, thus far, been unexplained. Recent studies in individuals with complete callosotomy and exclusive left hemisphere speech production show a reliable left-hand preference for co-speech gestures, indicating a right hemispheric generation. However, the findings raise the issue if the separate right hemisphere is able to also generate representational gestures. The present study challenges the proposition of a specific right hemispheric contribution to gesture production by differentiating gesture types including representational ones in individuals with complete callosotomy and by including individuals with anterior callosotomy in whom neural reorganization is less extensive.

METHODS

Three right-handed individuals with complete commissurotomy (A.A., N.G., G.C.) and three right-handed individuals with anterior callosotomy (C.E., S.R., L. D), all with left hemisphere language dominance, and a matched right-handed neurotypical control group (n = 10) were examined in an experimental setting, including re-narration of a nonverbal animated cartoon and responding to intelligence questions. The participants' video-taped hand movement behavior was analyzed by two independent certified raters with the NEUROGES-ELAN system for nonverbal behavior and gesture. Unimanual right-hand and left-hand gestures were classified into eight gesture types.

RESULTS

The individuals with complete and anterior callosotomy performed unimanual co-speech gestures with the left as well as the right hand, with no significant preference of one hand for gestures overall. Concerning the specific gesture types, the group with complete callosotomy showed a significant right-hand preference for pantomime gestures, which also applied to the callosotomy total group. The group with anterior callosotomy displayed a significant left-hand preference for form presentation gestures. As a trend, the callosotomy total group differed from the neurotypical group as they performed more left-hand egocentric deictic and left-hand form presentation gestures.

DISCUSSION

The present study replicates the finding of a substantial left-hand use for unimanual co-speech gestures in individuals with complete callosotomy. The proposition of a right hemispheric contribution to gesture production independent from left hemispheric language production is corroborated by the finding that individuals with anterior callosotomy show a similar pattern of hand use for gestures. Representational gestures were displayed with either hand, suggesting that in particular right hemispheric spatial cognition can be directly expressed in gesture. The significant right-hand preference for pantomime gesture was outstanding and compatible with the established left hemispheric specialization for tool use praxis. The findings shed a new light on the left-hand gestures in neurotypical individuals, suggesting that these can be generated in the right hemisphere.

Encouraging pointing with the right hand, but not the left hand, gives right-handed 3-year-olds a linguistic advantage

Previous research has shown a strong positive association between right-handed gesturing and vocabulary development. However, the causal nature of this relationship remains unclear. In the current study, we tested whether gesturing with the right hand enhances linguistic processing in the left hemisphere, which is contralateral to the right hand. We manipulated the gesture hand children used in pointing tasks to test whether it would affect their performance. In either a linguistic task (verb learning) or a non-linguistic control task (memory), 131 typically developing right-handed 3-year-olds were encouraged to use either their right hand or left hand to respond. While encouraging children to use a specific hand to indicate their responses had no effect on memory performance, encouraging children to use the right hand to respond, compared to the left hand, significantly improved their verb learning performance. This study is the first to show that manipulating the hand with which children are encouraged to gesture gives them a linguistic advantage. Language lateralization in healthy right-handed children typically involves a dominant left hemisphere. Producing right-handed gestures may therefore lead to increased activation in the left hemisphere which may, in turn, facilitate forming and accessing lexical representations. It is important to note that this study manipulated gesture handedness among right-handers and does therefore not support the practice of encouraging children to become right-handed in manual activities. RESEARCH HIGHLIGHTS: Right-handed 3-year-olds were instructed to point to indicate their answers exclusively with their right or left hand in either a memory or verb learning task. Right-handed pointing was associated with improved verb generalization performance, but not improved memory performance. Thus, gesturing with the right hand, compared to the left hand, gives right-handed 3-year-olds an advantage in a linguistic but not a non-linguistic task. Right-handed pointing might lead to increased activation in the left hemisphere and facilitate forming and accessing lexical representations.

Hand Preference in Adults’ Referential Gestures during Storytelling: Testing for Effects of Bilingualism, Language Ability, Sex and Age

Previous studies have shown that gestures are mediated by the left hemisphere. The primary purpose of this study was to test whether most gestures are also asymmetrical, i.e., produced with the right hand. We also tested four predictors of the degree of right-hand gesture use: bilingualism, language ability, sex, and age. These factors have been related to differences in the degree of language lateralization. English monolinguals, French–English bilinguals, and French monolinguals watched a cartoon and told the story back. For the gestures they produced while speaking, we calculated the percentage produced with the right hand. As predicted, the majority of gestures were right-handed (60%). Bilingualism, language ability, and age were not significantly related to hand choice in either English or French. In English, males tended to produce more right-handed gestures than females. These results raise doubts as to whether hand preference in gestures reflects speech lateralization. We discuss possible alternative explanations for a right-hand preference.

The Role of Gesture in Communication and Cognition: Implications for Understanding and Treating Neurogenic Communication Disorders

When people talk, they gesture. Gesture is a fundamental component of language that contributes meaningful and unique information to a spoken message and reflects the speaker's underlying knowledge and experiences. Theoretical perspectives of speech and gesture propose that they share a common conceptual origin and have a tightly integrated relationship, overlapping in time, meaning, and function to enrich the communicative context. We review a robust literature from the field of psychology documenting the benefits of gesture for communication for both speakers and listeners, as well as its important cognitive functions for organizing spoken language, and facilitating problem-solving, learning, and memory. Despite this evidence, gesture has been relatively understudied in populations with neurogenic communication disorders. While few studies have examined the rehabilitative potential of gesture in these populations, others have ignored gesture entirely or even discouraged its use. We review the literature characterizing gesture production and its role in intervention for people with aphasia, as well as describe the much sparser literature on gesture in cognitive communication disorders including right hemisphere damage, traumatic brain injury, and Alzheimer's disease. The neuroanatomical and behavioral profiles of these patient populations provide a unique opportunity to test theories of the relationship of speech and gesture and advance our understanding of their neural correlates. This review highlights several gaps in the field of communication disorders which may serve as a bridge for applying the psychological literature of gesture to the study of language disorders. Such future work would benefit from considering theoretical perspectives of gesture and using more rigorous and quantitative empirical methods in its approaches. We discuss implications for leveraging gesture to explore its untapped potential in understanding and rehabilitating neurogenic communication disorders.