Mean proportion of total looking time to the face that matched the heard voice in each condition (IDS, ADS) and for each age group (6-, 9-, 12-month-olds).

<p><i>Note</i>: *<i>p</i> < .05; Error bars represent <i>SD</i>s.</p

Schematic representation of the procedure.

<p>Infants saw two side-by-side silent video-clips presenting a male and a female face reciting a nursery rhyme. A soundtrack with a female or a male voice telling a story in IDS or ADS was played at the same time. The video-clips were repeated twice throughout the four trials, with left-right reversal for the positioning of the faces. (The individuals in this figure have given written informed consent (as outlined in PLOS consent form) to publish their pictures.)</p