Edited by: Yury Y. Shtyrov, Aarhus University, Denmark
Reviewed by: Adolfo M. García, Laboratory of Experimental Psychology and Neuroscience, Argentina; Véronique Boulenger, UMR5596 Dynamique du Langage, France
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The role of the sensorimotor system in second language (L2) semantic processing as well as its clinical implications for bilingual patients has hitherto been neglected. We offer an overview of the issues at stake in this under-investigated field, presenting the theoretical and clinical relevance of studying L2 embodiment and reviewing the few studies on this topic. We highlight that (a) the sensorimotor network is involved in L2 processing, and that (b) in most studies, L2 is differently embodied than L1, reflected in a lower degree or in a different pattern of L2 embodiment. Importantly, we outline critical issues to be addressed in order to guide future research. We also delineate the subsequent steps needed to confirm or dismiss the value of language therapeutic approaches based on embodiment theories as a complement of speech and language therapies in adult bilinguals.
The term “embodiment” refers to the grounding of cognition in systems involved in low level perceptual and action information processing. Embodied theories of cognition claim that higher cognitive processing, including language, activates the same brain sensorimotor structures involved when experiencing the environment (e.g.,
The idea that language processing activates sensorimotor areas of the brain has been supported by neuroimaging and neuromodulation studies focusing on the processing of nouns, adjectives, verbs and sentences including actions performed by specific body parts or manipulable objects. These studies suggested that primary and secondary motor cortices were regularly involved (
In the clinical setting – following the seminal work by
Note that to keep the focus of the present paper specifically on embodiment and second language lexico-semantic representations and processing (and the subsequent clinical implications), we only briefly mention the work on embodiment
Current models of bilingualism assume that, when processing a word (either in L1 or L2), after an initial language specific visual processing (
In addition to language proficiency, more global exposure to L2 environment plays a role in semantic processing (e.g.,
Semantic representations in bilingual models are therefore differently influenced by proficiency, exposure and age of acquisition, all factors to be taken into account in predicting embodiment in L2.
Despite some evidence suggesting sensorimotor involvement in L1 semantic processing, to our knowledge, only few studies have investigated such involvement in L2 processing. The lack of studies on the topic could be explained by two different, yet related assumptions. First, when considering early bilinguals, given that both languages are learnt in the same cultural context
Transferring this assumption into clinical predictions, the assessment and rehabilitation of a patient in L2 – acquired late and/or less proficient – could depend on the patient’s embodiment of L1 as well as the possible transfer between languages. It could also depend on the way the two languages are stored. Even if – as assumed by models considering separate stores of concepts for both languages (e.g.,
Investigating the sensorimotor activation in L2 – and its therapeutic context – could also offer some insight on models of L1, providing further understanding of the timing of sensorimotor involvement in language processing. Besides this debate (e.g.,
Although we have, so far, only presented L2 and embodiment as predictions and conjectures, some studies specifically addressing this issue do exist, and we critically discuss them next, raising some of the remaining open questions not yet answered. To facilitate a global perspective on those studies, we present in
Methodological description of the reviewed studies.
Authors | Type of study | L1 | L2 | N for analyzed data | Proficiency | Immersion | AOA | Task | Stimuli |
---|---|---|---|---|---|---|---|---|---|
Behavioral | Experiment 1: L1 English; Experiment 4: L1 various, L2 English | English | 39 (experiment 1); 35 (experiment 4) | General: High (students with a min TOEFL score). Task-specific: passive lexical knowledge test | Not reported | Not reported | Forced choice matching task | Verbs (written and imaged) | |
Behavioral | Italian | English | 23 | High, C1 (CEFR) | Not reported | Not reported | Go-no go paradigm | Photos and nouns of graspable and non-graspable objects; pseudowords and scrambled images | |
Behavioral (Experiment 1) | German | English | 20 | Not reported | Not immersed. Participants never lived in English speaking country | Late bilinguals.11–13 y.o. | Modified Stroop (response to the words’ ink color with an upward or downward arm movement) | Written L1 and L2 words referring to entitieswith a typical location (e.g., star, mole) | |
Behavioral (Experiment 2) | German | English | 20 | Not reported | Not immersed. Participants never lived in English speaking country | Late bilinguals.11–13 y.o. | Written L2 words referring to entitieswith a typical location (e.g., star, mole) | ||
Behavioral (Experiment 3) | German | English | 20 | Not reported | Not immersed. Participants never lived in English speaking country | Late bilinguals.11–13y.o. | Written L2 words referring to an emotion (e.g., happy, sad) | ||
Behavioral | Dutch | English | 20 | High (self-reported 6.5 on a 7-point Likert scale) | Varying: |
Judge whether presented pictures depicted something mentioned in a previously heard sentence | English sentence-picture pairs using interlingual English–Dutch homophones (e.g., “bone,” which in Dutch sounds likethe word “boon” [beans]/bo:n/) occurring in the final position. | ||
Behavioral | Group 1: German; group 2: Russian and English; group 3: Turkish and Korean | German | Group 1: 47; group2: 45; group 3: 42 | From A2 to C2, self-reported CEFR levels | Immersed. All participants were students or employees in Germany | Group 2: 8–28 y.o.; group3: 3–26 y.o. | Modified Stroop (response to the words’ ink color with an upward or downward arm movement) | Spatial prepositions: “auf”, “unter” and “über” and the filler “ab” | |
Behavioral | Chinese | English | 30 (15 per group) | High (group A) and low (group B). Group A has passed the test for English Majors Band 4 (TEM-4), while group B has no certificate of College English Test Band-4 (CET-4) | All participants lived in China. No immersion reported. Group A students are majoring in English | Not reported | Semantic judgment | Written high vs. low power nouns in L1 and L2 | |
Behavioral (eye-movementmeasures) | French | English | 34 | Self-reported measures: modified LEAP-Q; |
Self-reported measures: modified LEAP-Q; |
Not reported | Natural sentence reading | Semantically neutral sentences in whichembedded L2 target words varied onemotional valence (negative, neutral andpositive), frequency and concreteness | |
Neurophysiological (fMRI) | Group 1: Dutch group 2: German | Dutch | Group 1: 20 group 2: 18 | High (min. 67.5% accuracy in a online lexical decision task, LexTALE) | At least 1.5 years living in the Netherlands plus regular usage of L2 | Late: |
Lexical decision task | Written motor- and non-motor cognate and non-cognate verbs/pseudwords | |
Neurophysiological (EEG) | Chinese | English | 17 | High (near-balanced), assessed with a self rating scale, and all passed a national test for English majors, similar to TOEFL | Students majoring in English, but living in China | Not reported | Sentence acceptability judgment | Written high and low BOI words embedded in segmented sentences characterized by rich and poor sensorimotor context | |
Neurophysiological (EEG) | German | English | 18 | High, measured by self-rated proficiency scores (7-point Likert scale, |
Not reported. Participants started learning English as part of formal education in Germany | Late (mean 10.19 y.o., |
Passive reading | Written L1 and L2 action and abstract prime-probe verb pairs | |
Neurophysiological (EMG) | Dutch | English | 26 | Good fluency self-reported | Not reported | Late (after 12 y.o.) | Passive exposure to affirmative and negative sentences followed by a simple classification of arrow directions (left orright) | Written L2 affirmative and negative sentences either relevant (e.g., |
|
Neurophysiological (EMG) | English or Spanish | Spanish or English | 26 | Advance level self assessed from 1 to 10 (LEAP-Q; |
At least 12 months in their L2 speaking country | Not clearly reported. Most of them have a late AoA (started to learn L2 in a classroom setting) | Facial muscle EMG activity and SC responses were obtained during the encoding phase of a classical memory task, in which participants performed a categorization task, which required them to categorize words into “associated to emotion” or “not associated to emotion.” | Written L1 and L2 emotion-laden words | |
Theoretical description of the reviewed studies.
Authors | Aim of the study | Comparison | Embodiment effect | Conclusions on L2 embodiment | L2 vs. L1 embodiment | |
---|---|---|---|---|---|---|
Behavioral | To investigate if (1) action and language understanding use the same motor circuitry and if (2) this motor activation plays a functional role in language understanding | Descriptive comparison between L1 and L2 and between subjects | Slower RTs when the image and verb shared an effector, than when they did not share an effector | “Like native speakers, these nonnative speakers relied on motor structure activation to understand words” “Language proficiency (as measured by overall accuracy in the main experiment) correlated positively with effect size” |
L2 is embodied/ No statistical comparison with L1 | |
To test if L2 speakers showed the same kind of modulation of motor responses as participants in a previous experiment ( |
Descriptive comparison between L1 and L2 and between subjects (previous study |
Slower RTs during the processing of graspable items as compared to non-graspable ones | “Fluent speakers of English as L2, showed the same kind of modulation of motor responses as participants in a previous experiment ( |
L2 is embodied/ No statistical comparison with L1 | ||
To investigate basic associations between L2 and the sensorimotor system | Statistical comparison between L1 and L2 within subjects | Compatibility effect, reflected in an interaction between the implicit location of words and the direction of the response movement | “L2 automatically activated motor responses similar to L1 even when L2 was acquired rather late in life (age > 11)” “Reactivation of experiential traces is not limited to L1 processing” |
No difference between L2 and L1 embodiment | ||
None | Compatibility effect, reflected in an interaction between the implicit location of words and the direction of the response movement | L2 is embodied/ No statistical comparison with L1 | ||||
None | Compatibility effect, reflected in an interaction between emotion words (e.g., happy, sad) and the direction of the response movement | L2 is embodied/ No statistical comparison with L1 | ||||
To investigate the automaticity of embodied simulatory processes in language comprehension, exploiting the fact that both languages are activated during comprehension in bilinguals | None | Slower RTs to target stimuli in the homophone condition, suggesting activation of both languages which, in turn, led to greater competition between alternative meanings | “Perceptual simulation of L1 meaning occurs during L2 sentence processing” |
L2 is embodied/ No statistical comparison with L1 | ||
To compare embodiment effects related to the processingof spatial prepositions in German native speakers with the embodiment effectspotentially observed in different groups of L2 learners | Statistical comparison within language (German as L1 and as L2) and between subjects | Compatibility effect, reflected in an interaction between the meaning of the spatial prepositions and the direction of the response movement | “Reactivation of experiential traces plays an important role not only in L1 processing but also in the processing of L2, even if this “We found [...] also clear differences between speakers of different L1s” + “L2 language proficiency modulate the embodiment effect” |
L2 is embodied, but differently from L1 | ||
Investigate if (1) Chinese English learners with different proficiency levels activate vertical spatial metaphors in processing power words, and if (2) L2 proficiency has an impact on the mental representations in processing power words | Statistical comparison between L1 and L2 within participants, and statistical comparison within L2 between participants (high vs. low proficient) | Faster RTs for power words presented in the upper vs. lower part of the screen | “Chinese English learners tend to show stronger mental representation abilities to their first language than their second language” “High-level second language learners have stronger representation ability than low-level learners in understanding English words of power” “For RT, there’s an interaction between power words and L2 proficiency. [..] Learners’ second language proficiency had an impact on their mental representation ability.” |
L2 is embodied, but differently from L1 | ||
To investigate if bilingual readers (1) exhibit L2 emotional word processing effects, (2) show facilitation of negative words byconcreteness, like neutral words, and if (3) differences in L2 proficiency predict facilitationby concreteness and frequency, but not emotionality | Statistical comparison within L2 across participants with varying L2 proficiency and statistical comparison within language (English as L1 and as L2) between participants (previous study |
Shorter gaze duration (concreteness facilitation) for negative and neutral low-frequency words, but only at high levels of proficiency | “Previous work on L1 embodiment indicates that a concreteness advantage, where observed, is diagnostic of emotional neutrality because it does not occur for emotionally charged words ( “Bilinguals have emotionally disembodied negative words during L2 reading, and that these words are instead grounded in sensorimotor experiences like neutral words.” “L2 proficiency predicts concreteness advantages but not emotional advantages during natural reading.” |
L2 is embodied, but differently from L1 | ||
Neurophysiological | (Among others) to investigate if L2 speakers show embodiment effects like L1 speakers | Statistical comparison between Dutch as L1 and Dutch as L2 between participants | Motor verbs yielded significantly higher activation in sensorimotor ROIs than non-motor verbs | “Both groups |
No difference between L2 and L1 embodiment | |
To investigate if (1) richer sensorimotor context lead to increased sensitivity to the anticipated sensorimotor consequences of BOI effect, and if (2) the context and use of BOI word processing activate sensory-and motor-related brain areas | None | Sensorimotor context had an impact on the processing of BOI words that this modulation did activate related sensorimotor areas | “Action- and perception-related brain areas for L2 words are activated, indicating that the semantic representations for L2 learners are rich enough for the sensorimotor-related activation.” |
L2 is embodied/No comparison with L1 | ||
To investigate if the motor cortex of bilingual subjects shows differential involvement in processingaction semantics of native and non-native words | Statistical comparison between L1 and L2 within participants | Action related words elicited increased motor brain activity reflected in stronger ERD | “Processing of action verbs was accompanied byearly motor activation for probe stimuli in both languages of bilingual subjects, as reflected in desynchronisation of the EEG mu rhythm. Furthermore, at the level of sensor data and source activation clusters, we observed that this motor activation is stronger in the L1, likely due to highly integrated action–perception circuits formed as a result of rich linguistic experience.” At the sensor level, L1 probes elicited a larger desynchronization in the right-hemisphere cluster than L2 probes did; at the source level, L1 action primes, unlike L2 ones, produce more ERD. |
L2 is embodied, but differently from L1 | ||
To examine if the processing of affirmativeand negative sentences in L2 relies on the same somatic bases as that of L1 ( |
Statistical comparison between L1 and L2 between participants (across studies, L1 data from |
When participants readaffirmative sentences (e.g., ‘I am smiling’) the relevant muscle (i.e., zygomatic major) activates; however, when they read negativesentences (e.g., ‘I am not smiling’), the relevant muscleis inhibited only in L1 | “The magnitude of the somatic reaction in L2 is smaller than the one reported for L1” “The weaker magnitude of the somatic simulation for L2 compared to the one reported for L1 is generally in line with the argument that the different socialization histories of L1 and L2 are reflected in different degree of embodiment” For affirmative relevant sentences: L1 shows larger activation compared to L2 at 600 and 1000 ms period with the 800ms period showing a marginal significant difference. For negative relevant sentences, significant relaxation/inhibition in L1 and no effect in L2. |
L2 is embodied, but differently from L1 | ||
To investigate the link between embodied processes and memory for emotional content within the frame of L1 and L2 processing | Statistical comparison between L1 and L2 within participants | Differential activation in the zygomaticus and corrugator muscle in response to happy vs. angry words | “The overall results of the EMG and SC recordings suggested some reductions and differences in embodied simulations of emotional L2 words in comparison with emotional L1 words” “The difference between L1 and L2 processing became particularly clear in the corrugator muscle, which showed typical response patterns to emotional L1 words but no detectable responses to emotional L2 words.” “The present results complement and extend Foroni’s results showing a significant difference for the corrugator muscle and, thus, together they support an embodiment account of emotion processing and a reduced embodiment in L2.” Result indicates a later onset and shorter duration of specifiable zygomaticus activity in response to happy vs. angry words in L2 compared with L1 |
L2 is embodied, but differently from L2 | ||
In a similar vein, in
According to
In their adapted Stroop task,
Others have been less inclined to suggest that L2 was embodied, at least as strongly as L1. For example,
Still, a number of language studies, in which emotional valence of the stimuli was manipulated, have also observed differences in L1 and L2 affective processing, suggesting that the languages may be embodied to a different extent, especially in the case of late acquired L2 (
In sum, behavioral studies revealed that L2 is very likely embodied. Firm conclusions regarding the degree to which L2 is embodied remains to be clarified, as some studies report differences in L1 vs. L2 embodiment (
To our knowledge,
In a similar vein,
Other studies including neurophysiological measures have also supported the notion that bilinguals’ L2 is less embodied than L1.
These results are corroborated by those of
Some studies on bilingualism and emotions (e.g.,
In sum, (neuro-)physiological data globally confirm findings from behavioral ones on L2 embodiment, independent of the techniques used. Some issues still remain unanswered though, especially those pertaining to the degree by which L2 is embodied and to the roles of AoA, proficiency and immersion (see
The role of the sensorimotor system in L2 language processing has not received much attention, yet we have tried to gather and collate the few studies specifically focused on this issue. Crucially, all these studies show an embodiment effect during the lexico-semantic processing of L2 (see
Interestingly, eight out of the twelve studies reported in this review
Several studies suggest an influence of participants’ L2 proficiency on the degree of L2 embodiment. In terms of the RHM model (
One could further argue that even if proficiency was to be carefully assessed, any embodiment effect could also be accounted for by factors such as exposure to L2 and/or AoA. If the degree of embodiment of L2 depends on the degree to which L1 and L2 share their semantic representations, some models (e.g.,
In fact, the importance of the type of learning for L2 embodiment may be illustrated by studies which show a rapid association between motor areas’ activation, or excitability, and novel labels attributed to actions or tools (e.g.,
Another factor that could account for differences between L1 vs. L2 embodiment is the linguistic distance between languages, which refers to the extent of similarity between the languages and which has previously been shown to play a role in bilingual language processing (e.g.,
This issue is nonetheless relevant, especially in studies that (a) involve words with a special status (e.g., cognates, as in
Others have stressed the timing of the motor system involvement as an explanatory factor for the difference between L1 and L2 embodiment. Differences both in the onset of the motor resonance and its duration have been reported by
Arguably, these potential explanatory factors – all legitimate – raise an important issue, as to the stages of cognitive processing under investigation. Accordingly, any endeavor to investigate embodiment in L2 should always be very explicit as to which stage of processing is under investigation. This is crucial, as the majority of the studies on this topic used tasks which allegedly access early stages of lexical processing (e.g., a Stroop task or a lexical decision task, where the access to meaning is not necessary;
Importantly, all explanatory factors – to differences between L1 and L2 embodiment – presented so far have been based on studies on
No clinical study has apparently explicitly linked the sensorimotor system to L2 lexico-semantic processing. Nonetheless, some studies on bilingual patients with motor impairment did explore motor-language interactions, yet with somehow different purposes (e.g., syntactic impairment). In the next section, we discuss these studies and corollary hypotheses related to lexico-semantic processing. In the following section, we present some clinical rehabilitation studies – in L1 – that could be interpreted in terms of embodiment (e.g., language-action therapies in aphasic patients) and then extend the discussion to L2, and bilingual rehabilitation outcomes.
Clinical studies on the interaction between motor and L2 language systems have been scarce, yet could document the modulation of motor impairment on L2 processing as well as the impact of L2 impairment on sensorimotor systems.
In Section “Embodiment Predictions for L2 and Their Impact on Language Models” we discussed the idea that L2 lexico-semantic representations should be less grounded in the sensorimotor system – the motor cortex – if L2 is acquired through late explicit learning. This is reminiscent of the Procedural/Declarative model of language acquisition (
Whilst proficiency, exposure to L2 and AoA were not always carefully considered in studies on healthy participants, these factors were more thoroughly reported in
Data on bilingual Parkinsonian patients also illustrate the Disrupted Motor Grounding Hypothesis (DMGH;
Importantly, and central to the present paper, the DMGH also predicts lexico-semantic deficits in motor-related disorders. According to the DMGH, action-related meanings, in a somatotopic manner, are mapped onto motor circuits. Accordingly, semantically processing action words and sentences, as well as integrating verbal and motor information, should also be impaired in Parkinsonian patients, which seems to be the case (
Questions remain as to the use of linguistic diagnostic tasks in L2. At this point, there is no data to evaluate patients’ sensitivity to L2 tasks that evaluate the processing ease of motion-related verbal expressions. Depending on the grounding of L2, a simple use of a diagnostic L1 task (yet to be generated) may not be adequate. Factors such as AoA and language competence may be critical, together with the presence of emotionally charged content, which might be perceived very differently depending on the language in use (i.e., L1 or L2, see
In sum, actual evidence on
Although
We believe that, however, weak the
As mentioned earlier, experimental manipulations of language in healthy monolinguals (e.g.,
With respect to neuromodulation interventions, transcranial direct current stimulation (tDCS) and TMS of the motor cortex of aphasic patients is of particular interest. While brain stimulation is increasingly being tested as promising auxiliary therapeutic tools in patients with aphasia, results have so far been inconsistent, the activation of different brain regions showing very different efficacy (
With respect to behavioral interventions, we believe several methods to be relevant. Therapists can choose, for example, to reinforce the damaged language-specific neural network by training the specific language impairment or to work on a more general cognitive-control network reinforcing executive functions, or, in light of the studies on embodiment mentioned so far, strengthen the sensorimotor circuit. Several speech and language therapeutic approaches that are based on the interaction between the motor and the language systems, as in embodiment theories, have in fact shown promising results (e.g., Semantic Feature Analysis therapy,
The Semantic Feature Analysis therapy (SFA,
Finally, in regard to the issues mentioned so far, one does wonder whether experimental manipulations of the language system may also produce promising effects on the impaired motor system in monolingual and bilingual patients. Some studies do hint that this may be a promising line of research (e.g.,
Of course, studies on L2 acquisition may be of special interest in future work on this topic too, as rehabilitation and learning may be grounded on similar mechanisms (e.g., motor areas response to learning the meaning of novel action words in
There are many challenging paths in this topic ahead of us, and for any rigorous attempt to better understand lexico-semantic embodiment in L2, we would suggest three critical issues to seriously consider. First, although all studies on the topic have concentrated on a
We believe that this shift in treatment approaches – merging traditional speech and language therapies with a motor integrated perspective – opens new directions in bilingual aphasia rehabilitation. We argue, though, that three necessary issues need to be further addressed and clarified in future studies. First, due to the scarce literature on the subject, additional pre-registered and randomized controlled studies need to be conducted to confirm that therapies based on sensorimotor activation do indeed improve L1 language processing, specifically for sensorimotor-related stimuli in aphasics. Second, clear evidence needs to be provided to show that the same therapy can improve L2 language processing, again, specifically for sensorimotor-related stimuli in aphasics. To our knowledge, only
In light of the exponential increase in multilingual populations worldwide, a better understanding of the mechanisms underlying the interplay between neural structures involved in the processing of more than one language is central. The sensorimotor embodiment account offers an opportunity to further our knowledge in several areas of research, including semantic processing in mono- and bilinguals, language learning, neural mechanisms of language processing and rehabilitation in L2. Overall, all the reviewed studies investigating sensorimotor involvement in semantic processing showed that L2 is – at least to some extent – embodied. Further investigating the factors influencing the degree of L2 embodiment is relevant from a theoretical point of view, of course, but also to confirm or dismiss the value of language therapeutic approaches based on embodiment theories as a complement of speech and language therapies in bilinguals. We have outlined several important issues to tackle in the future, and hope that these will be taken as a sign to encourage rigorous and innovative research in this topic, both in a theoretical and applied perspective.
All authors listed have made a substantial, direct and intellectual contribution to the work, and approved it for publication.
The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest.
We are very grateful to PD Dr. Lucas Spierer for the helpful comments and discussions throughout the preparation of the manuscript. We thank the two reviewers for their valuable input.
Other examples of studies on L2 acquisition and embodiment are provided in the Section “Critical Synthesis.”
Here we do not discuss the case of bicultural bilinguals, but reader
Cognates are words that share orthographic and/or phonologic features between languages (e.g.,