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The influence of maternal speech during pregnancy affects the language preferences of newborns. Babies recognize stories they heard in utero and show a preference for their mother’s voice and native language. However, the impact of maternal monolingualism or multilingualism on the fetal neural mechanisms underlying the encoding of speech sounds remained unclear. Scientists from the University of Barcelona studied how bilingual mothers impact their infants’ speech-encoding abilities and the development of their speech.
Infants Learn Language Even Before Birth
The process of language acquisition has long been a subject of uncertainty in studies exploring the roots of human language. Today, it is known that both genetic and empirical factors influence language learning. After birth, infants demonstrate advanced language perception and learning abilities. Newborns prefer human speech over other sounds, can distinguish different languages based on their rhythm, identify word boundaries, and mimic the pitch of an adult’s voice.
At the same time, the prenatal period also involves language experience. Hearing becomes functional and undergoes most of its development around the 26th-28th week of pregnancy. According to research, the maternal womb acts as a low-frequency filter, attenuating approximately 30 dB for frequencies above 600–1000 Hz. The low-frequency components of speech that pass through the womb include pitch, slow aspects of rhythm, and some phonetic information. Due to this experience, the baby recognizes the mother’s voice, stories heard during prenatal development, and the native language after birth.
Bilingual Skills and the Brain
Approximately 65% of residents in European countries are proficient in at least two languages. Research increasingly shows that a bilingual environment and the learning of multiple languages impact perception, cognition, and brain development. Additionally, some bilingual individuals switch between languages within a single sentence, requiring greater cognitive control than monolinguals.
It is known that infants can distinguish all phonetic contrasts. Though, as they grow, their ability to differentiate phonetic elements becomes more specific to their native language. Bilingual infants show different brain responses to sounds of their native and non-native languages compared to monolinguals. Newborns who were exposed to a bilingual environment prenatally can distinguish their two native languages immediately after birth and exhibit equal preferences for both. However, the mechanism of maternal bilingual linguistic influence remained unknown.
About the Study
Researchers recruited 131 newborns (average age post-birth = 38.32 ± 23.8 hours) from Sant Joan de Déu Children’s Hospital in Barcelona. A socio-demographic questionnaire was used to measure maternal education and musical exposure.
The infants were divided into monolingual and bilingual groups based on the language used by their mothers during the last trimester of pregnancy. Among the bilingual mothers, 77.3% spoke both Spanish and Catalan, while other languages included Arabic, English, Galician, German, Italian, Portuguese, Guaraní, and Romanian. Mothers in the monolingual group spoke either Spanish (90.6%) or Catalan (9.4%).
The team identified 53 newborns from monolingual environments and 76 from bilingual environments. All infants had an APGAR score of ≥8.0 at the first and fifth minutes of life. Additionally, all passed the universal newborn hearing screening positively.
Analytical Tools
To assess speech encoding in 29 healthy newborns from monolingual or multilingual environments during the last trimester of pregnancy, researchers used a parameter called the frequency-following response (FFR). This parameter relates to the acoustic characteristics of speech sounds—specifically, the response to pitch, frequency, and timbre of the voice.
Additionally, they evaluated the click-evoked auditory brainstem response (ABR) to sound stimuli, particularly clicks, to assess the integrity of the auditory pathway. Data were processed using band-pass filtering and averaging of neural responses to highlight different components of speech encoding.
Bilingual Environment Boosts Language Perception Flexibility
Newborns of multilingual mothers had a lower spectral signal-to-noise ratio (SNR). Monolingual newborns showed higher spectral amplitude and SNR. The signal-to-noise ratio is a measure that determines how much the signal is distorted by noise.
Simply put, infants from multilingual environments are more sensitive to a broader range of speech frequencies than those of monolingual mothers.
