Control study S1: Effects of task order on infant visual preferences (eye-tracking only).

Control study S2: Auditory speech sounds only (ERP study).

Control Study S3. Responses to audio-visual speech stimuli in adult participants (ERP study).

Fig. S1. ERP responses to auditory only and audiovisual /ba/ and /ga/ syllables in infants.

Fig. S2. Channel groups selected for statistical analyses.

Fig. S3. Stimulus position and size in visual angle along with the positioning and size of the eyes and mouth Areas of Interest (AOIs) in eye-tracking study.

Fig. S4. ERP responses to AV stimuli in NMP group of infants.

Fig. S5. ERP responses to AV stimuli in MP group of infants.

Fig. S6. ERPs in the younger and the older group of infants.

Fig. S7. Results of study 3: Adult ERP responses to audiovisually congruent and incongruent stimuli.

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