Building a Word-Form Lexicon in the Face of Variable Input: Influences of Pitch and Amplitude on Early Spoken Word Recognition

Abstract

To build their first lexicon, infants must first be able to recognize words in the input. This task is made challenging by the inherent variability of speech. Potential sources of variability include changes in speaker identity, vocal emotion, amplitude, and pitch. English-speaking adults can recognize a word regardless of these changes, and mature word recognition is not impeded by changes in amplitude or pitch. In this set of studies, we independently manipulate amplitude and pitch to examine whether infants' lexical processing is similarly invulnerable to changes in surface form. We found that 7.5-month-old infants at the earliest stages of word recognition can recognize a word if it is presented in a different amplitude but not in a different pitch. By 9 months, infants are able to recognize words independent of changes in pitch and amplitude, thus appearing to appreciate the irrelevance of both properties in determining lexical identity. Results are interpreted with respect to why infants may treat pitch and amplitude distinctly in spoken word recognition.