title: Sound symbolism scaffolds language development in preverbal infants.
abstract: A fundamental question in language development is how infants start to assign meaning to words. Here, using three Electroencephalogram (EEG)-based measures of brain activity, we establish that preverbal 11-month-old infants are sensitive to the non-arbitrary correspondences between language sounds and concepts, that is, to sound symbolism. In each trial, infant participants were presented with a visual stimulus (e.g., a round shape) followed by a novel spoken word that either sound-symbolically matched ("moma") or mismatched ("kipi") the shape. Amplitude increase in the gamma band showed perceptual integration of visual and auditory stimuli in the match condition within 300 msec of word onset. Furthermore, phase synchronization between electrodes at around 400 msec revealed intensified large-scale, left-hemispheric communication between brain regions in the mismatch condition as compared to the match condition, indicating heightened processing effort when integration was more demanding. Finally, event-related brain potentials showed an increased adult-like N400 response - an index of semantic integration difficulty - in the mismatch as compared to the match condition. Together, these findings suggest that 11-month-old infants spontaneously map auditory language onto visual experience by recruiting a cross-modal perceptual processing system and a nascent semantic network within the first year of life.
authors.affiliation: Department of Psychology, College of Contemporary Psychology, Rikkyo University, Niiza, Saitama, Japan; Faculty of Environment and Information Studies, Keio University, Fujisawa, Kanagawa, Japan; Tamagawa University Brain Science Institute, Machida, Tokyo, Japan.
authors.forename: Michiko
authors.initials: M
authors.lastname: Asano
authors.affiliation: Faculty of Environment and Information Studies, Keio University, Fujisawa, Kanagawa, Japan. Electronic address: imai@sfc.keio.ac.jp.
authors.forename: Mutsumi
authors.initials: M
authors.lastname: Imai
authors.affiliation: Department of Psychology, University of Warwick, Coventry, UK.
authors.forename: Sotaro
authors.initials: S
authors.lastname: Kita
authors.affiliation: RIKEN BSI-Toyota Collaboration Center, RIKEN Brain Science Institute, Wako, Saitama, Japan; RIKEN Brain Science Institute, Wako, Saitama, Japan.
authors.forename: Keiichi
authors.initials: K
authors.lastname: Kitajo
authors.affiliation: Tamagawa University Brain Science Institute, Machida, Tokyo, Japan.
authors.forename: Hiroyuki
authors.initials: H
authors.lastname: Okada
authors.affiliation: School of Psychology, Bangor University, Gwynedd Wales, UK.
authors.forename: Guillaume
authors.initials: G
authors.lastname: Thierry
mesh_terms: D000161:Acoustic Stimulation; D001921:Brain / Q000502:physiology*; D004569:Electroencephalography; D005072:Evoked Potentials, Auditory / Q000502:physiology*; D005260:Female; D006801:Humans; D007223:Infant; D007802:Language; D007804:Language Development; D008297:Male; D013067:Speech Perception / Q000502:physiology*; D013561:Symbolism
keywords: Amplitude change analysis of EEG; Audio-visual correspondences; Language development; Phase synchronization analysis of EEG; Sound symbolism