Sounds elicit relative left frontal alpha activity in 2-month-old infants

• We examine responses of brain alpha wave to human voices in 2-month-old infants.
• Human voices elicit increased left relative to right frontal activity in infants.
• Human voices might elicit approach-related emotions in young infants.

As one kind of sounds, human voices are important for language acquisition and human–infant relations. Human voices have positive effects on infants, e.g., soothe infants and evoke an infant's smile. Increased left relative to right frontal alpha activity as assessed by the electroencephalogram (EEG) is considered to reflect approach-related emotions. In the present study, we recorded the EEG in thirty-eight 2-month-old infants during a baseline period while listening to sounds, i.e., human voices. Infants displayed increased relative left frontal alpha activity in response to sounds compared to the baseline condition. These results suggest that sounds can elicit relative left frontal activity in young infants, and that this approach-related emotion presents early in life.