If linguistic experience frees up resources for processing of visual information, then both deaf and hearing speakers of BSL should do best at remembering BSL stimuli. Similarly, if they can remember the phonological information in a word from another language that they do not speak (Swedish Sign Language), then their performance should be better than their memory for a nonsign “pseudo-word” which does not have sounds from BSL. Likewise, non-signers should process signs in both languages as well as non-signs and with greater difficulty than the signers.
The results of the study were intriguing. Ruder and colleagues found that speakers of BSL did better at remembering whether a BSL word was n trials back, but that despite knowing the sounds of words in Swedish Sign Language, they did not remember those words any better than nonsigns. That is, phonological information alone did not convey an advantage over a gesture fragment that did not contain any meaningful information.
The study also found that signers tended to outperform non-signers on nearly every type of stimulus except for the nonsigns, suggesting that speakers of signed languages process linguistic information differently: A lifetime of experience with a signed language seems to make sign and sign-like material easier to remember, showing that linguistic experience in general helps to compress information into smaller bits, freeing up working memory for other tasks—in this case the n-back recall of visual stimuli.
The study also revealed interesting differences between the hearing BSL and the deaf BSL speakers. The hearing BSL speakers also grew up listening to a spoken language, making them “bilingual” and sensitive to the phonological representations in speech. Deaf signers outperformed non-signers on both nonsigns and Swedish Sign Language, but hearing signers did not. This suggests that when hearing speakers of BSL encountered something clearly linguistic but unfamiliar, they engaged a different strategy that was more similar to hearing non-signers' strategies.
Altogether, the results of the study show that having the tools to process what can look like "just" visual stimuli to a non-signing person can actually have profound cognitive advantages. In fact, it can free up working memory resources to process other visual information.
This does not mean one should necessarily have a conversation in sign language while driving. But it does mean that one is better off conversing in English with a passenger than trying to encode and remember a recording of backward speech while driving.
Focus article of this post:
Rudner, M., Orfanidou, E., Cardin, V., Capek, C. M., Woll, B., & Rönnberg, J. (2016). Preexisting semantic representation improves working memory performance in the visuospatial domain. Memory & Cognition