The neurocognitive fingerprint of simultaneous interpretation

The human brain is a dynamic organ which is molded throughout the lifespan by each individual’s life experiences. Learning to juggle, speaking two languages, and playing the piano all number among experiences that leave an impression on the mind and brain. Little research, however, has examined one of the most demanding processes in human cognition, simultaneous interpretation (SI). In SI an individual must comprehend a stream of auditory material in one language and with a few seconds delay produce the same content in another language. This process, which is both a specialized form of bilingualism and a learned skill, similar to playing the piano, likely leaves its own distinct fingerprint on the mind and brain. The present work examines the neurocognition of professional and trainee simultaneous interpreters to better understand the process of simultaneous interpretation and the lasting impression it leaves. Bilingualism has been previously associated with advantages in cognitive control in both linguistic and non-linguistic domains. These benefits are posited to be due to bilinguals’ extensive practice managing two languages. Simultaneous interpretation represents a process which requires a higher level of language management than most bilingual contexts. This increased experience may lead to quantitatively larger benefits in interpreters than in bilinguals. Additionally, interpreters may garner benefits which are unique to the interpreting experience, in particular the need to use two languages simultaneously. The first study addressed these possibilities in an examination of professional interpreters and matched multilinguals on three tasks of cognitive control. The two groups showed no differences on the color-word Stroop and Attention Network Test, tasks which have previously revealed an advantage for bilinguals. Results from a non-linguistic task-switching paradigm were mixed. Interpreters showed no additional advantage in switching costs, where bilingual benefits have previously been seen, but exhibited smaller mixing costs than the multilinguals. In comparison with previous literature, this benefit in mixing cost appears to be unique to simultaneous interpretation. Additionally, the interpreters had larger verbal and spatial memory spans than the multilinguals. The results suggest that professional interpreters do not have quantitatively larger bilingual benefits, but do possess benefits specific to experience with simultaneous interpretation As simultaneous interpretation is an acquired skill, these interpreter-specific advantages may have been gained through training in SI or represent innate differences that led individuals to the field. The second study examined students earning a Master in Conference Interpreting, and matched students in other disciplines, longitudinally to determine which cognitive abilities are innate and which are acquired through SI training. The results indicated improvements in verbal and spatial memory among the students of interpretation, but not among the students in other disciplines, suggesting that these abilities are acquired with training. An improvement in the mixing cost, however, was seen across the groups, leaving open the possibility of an influence of professional experience on this measure. Previous studies of skill acquisition have indicated that not only cognitive abilities, but also underlying brain structure is altered through the training period. To examine the effects of training in simultaneous interpretation on gray matter and white matter structure the above-mentioned groups additionally participated in neuroimaging sessions. Analysis of gray matter volume using voxel-based morphometry (VBM) revealed group differences in regions previously linked to spoken word learning, suggesting greater efficiency in these areas among students of interpretation. Additionally, changes in gray matter volume related to training in SI were evident in bilateral putamen and left superior temporal cortex, among other regions. Previous functional MRI studies of speech shadowing have found activation in these same regions, suggesting the changes may be related to the simultaneity of input and output during simultaneous interpretation. Moreover, analyses of diffusion tensor imaging (DTI) data revealed greater white matter integrity among the students of interpretation in tracts in the left hemisphere that underlie language. A subset of these tracts was further strengthened through training in SI. Finally, the mechanisms supporting the simultaneous use of two languages were considered, specifically addressing the possibility that interpreters apply less inhibition to the unused language. Students at various stages in their simultaneous interpretation training were tested on a three language switching paradigm. This paradigm affords a measure of inhibition of abandoned task sets through n-2 repetition costs. Though differences were found between the groups on n-2 repetition costs, these did not appear to be connected to SI training, but rather the predominant bilingual interactional context of the groups. Taken together these investigations begin to provide a picture of the effects that simultaneous interpretation has on cognitive abilities and brain structure. Specifically, interpreters appear to have a unique set of cognitive advantages that are related to the processes used during SI. Further, these advantages originate from a combination of innate and trained abilities.