Perszyk, D. , Voss, J. & Waxman, S.
Northwestern University
To acquire language, infants must first distinguish the sounds of their native language and then ascertain how these sounds are linked to the objects and events they encounter. At 3 and 4 months, listening to both human (speech) and nonhuman primate vocalizations (Madagascar, blue-eyed lemur: Eulemur macaco flavifrons) support infants? object categorization, a core cognitive capacity (Ferry, Hespos & Waxman, 2010; 2013). By 6 months, only human speech confers this advantageous effect. Moreover, backward human speech-a sound equally complex to forward human speech-does not have this effect at any age. Here we use EEG to reveal the neural correlates of listening to these three types of sounds. Our results indicate that for 6-month-olds, both lemur vocalizations and backward speech elicit robust P300s in right parietal regions, suggesting that these unfamiliar sounds draw more of infants? attention relative to forward speech. In addition, lemur vocalizations elicit enhanced gamma activation (40-60Hz) in right frontal regions relative to forward or backward speech, suggesting that these sounds are affectively arousing (Muller, Keil, Gruber, & Elbert, 1999). Together, these results suggest that there may be multiple routes by which a signal can support infant cognition.