Babies are fast learners. Whether babies are raised as monolinguals or bilinguals, they seem to progress at the same pace in learning new words and understanding their meanings. By the age of 24 months, most babies are able to produce simple word combinations like “mommy bye-bye”, give responses or at least understand simple commands such as “No, no, cannot eat.” However, given that bilingual babies are exposed to two languages, one of which may be more familiar and one less familiar, researchers often wonder how babies organise words in their brain networks. How do babies learn the meaning of the same word across languages? Do they link words of the same meaning in different languages together?

Previously, a priming task by Von Holzen and Mani (2012) had revealed that German-English bilingual toddlers of 21 and 43 months showed rhyming associations between their second language (L2, English) and first language (L1, German). That is, a task where babies are more able to recognize a target word in German (L1) when preceded by a rhyming prime word in English (L2). For example, the participants are more able to recognise the German target word stein ‘stone’ when they were shown the English prime word leg right before it. The rationale is that the word leg, called bein in German, sounds similar to stein and would be activated in participants’ minds, so it would help facilitate participant’s subsequent recognition when they saw the word stein.

Besides doing research on infants’ word association of different languages, there are also studies that talk about the lexical semantic network, which is where meanings of words are linked together (see Figure below).

Semantic Network (Retrieved from Wikipedia ‘Semantic networks’, https://commons.wikimedia.org/w/index.php?curid=1353062)

For instance, other than the rhyme of bein and stein which can trigger a link, researchers wonder whether bilingual infants are able to exhibit priming when children need to think about the meanings of the words (not just the sounds) at the age of 18 and 24 months, and whether their vocabulary knowledge will affect how quickly they process the information. In other words, are 18- and 24-months bilingual children able to activate the meaning and understanding of both target and prime words when both words are presented in different languages? Also, would a bigger or smaller vocabulary size of the two languages affect the speed that children do this task? 

In a study done by De Anda and Friend (2020), thirty-two English- and Spanish-learning bilingual toddlers were recruited. Three types of tests were used in their study:

1. Computerized Comprehension Test (CCT)

A CCT is a test in which the infants were prompted to touch images on a touch-sensitive monitor. Infants were escorted to a dimly lit room with a caregiver. Two images (a target; a distractor) were presented simultaneously on the left and right monitor. The experimenters engaged the infants’ attention by speaking to them in infant-directed speech (speech that is exaggerated to keep infants interested). Infants had seven seconds to choose the correct image. For each trial that the infant failed to answer, the experimenter would touch the screen for them.

2. Intermodal Preferential Looking (IPL) Priming Task

In an IPL task, the experimenters first caught the infants’ attention with a spinning wheel at the beginning of the task. At the same time, infants also heard a sentence with a prime word that was either semantically related or unrelated to the target word.

After a small pause, the target word was played on its own. Finally, the target word was played at the same time as a distractor word. 

For example, a target word “apple” was presented for 200ms. In this case, the prime word used was “banana”, which belongs to the category of ‘fruit’, just like the target word “apple”.

The experiment consisted of four blocks: Spanish prime words to Spanish targets (Spanish-Spanish), Spanish prime words to English targets (Spanish-English), English prime words to English targets (English-English), and English primes to Spanish targets (English-Spanish). Each block consisted of three related trials (e.g., ‘apple’ in both languages) and three unrelated trials (‘apple’ in one language, ‘car’ in another language).

3. The MacArthur Bates Communicative Development Inventory (MCDI)

The MCDI is a parent report measure on a child’s early language. This is a checklist which parents get to indicate the words their child uses and understands. The Spanish version, IDHC (DEFINE ), was also used in this experiment. The MCDI consists of two additional measures, total conceptual vocabulary (total vocabulary size minus the translation equivalents) and translation equivalents (synonyms across two languages, e.g., ‘apple’ in English and manzana ‘apple’ in Spanish). 

Findings

1. Children’s vocabulary size in each language does not affect their speed in this task, no matter whether the prime and target words were in the same or different languages. 
2. Children with more translation equivalents across languages showed greater differences in looking time to semantically unrelated and related trials when the prime and target words were in the same language.
3. Children were more likely to learn a translation equivalent if the word was first learnt in the more-familiar language.
4. Bilingual children tend to use their knowledge from the other more-familiar language to support the less-familiar language. 

All in all, important language milestones seem to appear at the same time for both monolinguals and bilinguals. However, due to the dual language exposure, there are some complex links between vocabulary knowledge and the process of understanding the meanings of words in bilingual children’s language development.

Reference

De Anda, S. & Friend, M., (2020). Lexical-Semantic Development in Bilingual Toddlers at 18 and 24 Months. Frontiers in Psychology, 11, https://doi.org/10.3389/fpsyg.2020.508363 

This post was written by our intern, Hong Ern, and edited by our Research Fellow Rui Qi.