Multilingual Lexicon and what it tells us about Cognition and the Brain - Talk by Prof. John Schwieter

I attended a Talk titled "Multilingual Lexicon and what it tells us about Cognition and the Brain" by Prof. Schwieter where I had the opportunity to learn about the different methods used to understand how languages are processed and activated in an ordinary multilingual/bilingual individual.

These are few of my notes from this talk :

Different languages are constantly active regardless of whether only one language is shown in that moment ( e.g. A Spanish-English bilingual speaking in English ). This process is called co-activation. 

One of the questions that was answered in the talk was "How can we examine words and lexical processing in the brain?", in other words how do we understand what is happening in the brain when we switch from one language to another? There are two ways we can investigate lexical activation

1. Measuring Behaviour through priming, inhibitory controls and eye tracking

2. Measuring brain activity through fMRI, PET and EEG 

1. Measuring behaviour show the indirect measure of processing difficulty

Priming - when the participant is shown a stimulus ( word ) briefly before the target word - the participant would press a key and a blank screen would be shown, then a dot would be shown, after a word in red font would be shown for 50 ms ( stimulus ), then blank screen again, finally target word in white font, participant now need to say if they think that it a real word or not.

This method showed that if the prime was somehow related to the target the reaction either in L1 or L2, the reaction from the participant is faster. This shows that although the prime is only displayed on the screen for a short time, it is still processed in the brain and it affects the process of the target word.

e.g. Prime = Tendencia ( tendency in English ) - if the target was related to this prime in either English or Spanish, the reaction would be typically faster.

The relation of the prime and target can be phonetical, semantical etc

One study of priming is Jiang's (1999) where Chinese-English bilinguals underwent five different experiments that manipulated the directionality of the prime ( prime in L1 and target in L2 and viceversa ). There were consistent results that in L1 to L2 there were strong priming effects, in other words the reactions were faster. This shows that although both languages are active, their effectiveness is different.

Inhibitory Control - explains how languages are controlled, specifically how the non-target language is controlled and inhibited. One investigation that show this process is colour-cued picture naming tasks involving switching between languages ( e.g. the participant looks at a series of pictures and they have to name the different pictures, if the picture is enclosed in a red box in English and if the picture is enclosed in a blue box in Spanish ).

Once the association of colours and languages is solidified, many studies show that the switch from L2 to L1 is slower and less accurate.

This statistics can however be affected by other factors, such as the usage of homographs and cognate.

Homographs - words in different languages spelled the same but the pronunciation and the meaning is different. ( e.g. RED - in English, the colour - in Spanish, "net" )

Cognates - words in different languages with similar spelling and pronunciation ( e.g. class in English, clase in Spanish )

One study that show the effect of these type of words is Filippi et al. 2014 who investigated the inhibitory control in a language switching task - cognates and non-cognates - in Italian English bilinguals. The result demonstrated that there was a slower reaction for cognates than non- cognate which again show that competition for selection between languages.

2. Measuring brain activity consist of using electrical activity and blood flow to generate graphs and high resolution brain images 

Electroencephalograms ( EEG ) use electrical activity to generate graphs which are show clearly the time course of lexicon process. However Neuroimaging measures blood flow in the brain to generate high resolution images of the brain which show clearly the location of lexicon process, not the time course. 

One study by Van de Heuven et al. (2008) showed increased blood flow, especially in the left prefrontal cortex, for homographs. Van de Heuven investigated English-Dutch bilinguals using fMRI, and when the word "boom" was shown ( tree in Dutch ) there was an increased blood flow shown in the brain images.

In conclusion, languages in bilinguals/multilinguals are always active and they are constantly competing for selection and most of the time it tends to run smoothly. However when we add obstacles in this competition, it is clear that the brain needs more time processing and choosing the right language.