This article analyses longitudinal diary data from one infant acquiring German to seek a better understanding of the role of onomatopoeia in early language development. Onomatopoeic words (OWs) are traced over time in relation to their corresponding conventional forms (CWs), and an analysis of their phonological transitions is considered in relation to the infant's wider language development. OWs are found to serve as a bootstrapping mechanism on a lexical as well as a phonological level, and a lexical OW 'template' is proposed, which is found to support phonological development throughout the infant's output.

A perceptual advantage for iconic forms in infant language learning has been widely reported in the literature, termed the "sound symbolism bootstrapping hypothesis" by Imai and Kita (2014). However, empirical research in this area is limited mainly to sound symbolic forms, which are very common in languages such as Japanese but less so in Indo-European languages such as English. In this study, we extended this body of research to onomatopoeia-words that are thought to be present across most of the world's languages and that are known to be dominant in infants' early lexicons. In a picture-mapping task, 10- and 11-month-old infants showed a processing advantage for onomatopoeia (e.g., woof woof) over their conventional counterparts (e.g., doggie). However, further analysis suggests that the input may play a key role in infants' experience and processing of these forms.

Onomatopoeia are frequently identified amongst infants' earliest words (Menn & Vihman, 2011), yet few authors have considered why this might be, and even fewer have explored this phenomenon empirically. Here we analyze mothers' production of onomatopoeia in infant-directed speech (IDS) to provide an input-based perspective on these forms. Twelve mothers were recorded interacting with their 8-month-olds; onomatopoeic words (e.g. quack) were compared acoustically with their corresponding conventional words (duck). Onomatopoeia were more salient than conventional words across all features measured: mean pitch, pitch range, word duration, repetition, and pause length. Furthermore, a systematic pattern was observed in the production of onomatopoeia, suggesting a conventionalized approach to mothers' production of these words in IDS.

Onomatopoeia appear in high quantities in many infants’ earliest words, yet there is minimal research in this area. Instead, findings from the wider iconicity literature are generalised to include onomatopoeia, leading to the assumption that their iconic status makes them inherently learnable, thereby prompting their early production. In this review we bring together the literature on onomatopoeia specifically and iconicity more generally to consider infants’ acquisition from three perspectives: perception, production, and interaction. We consider these findings in relation to Imai and Kita’s (2014) ‘sound symbolism bootstrapping hypothesis’ to determine whether their framework can account for onomatopoeia alongside other iconic forms.

Infants' early babbling allows them to engage in proto-conversations with caretakers, well before clearly articulated, meaningful words are part of their productive lexicon. Moreover, the well-rehearsed sounds from babble serve as a perceptual 'filter', drawing infants' attention towards words that match the sounds they can reliably produce. Using naturalistic home recordings of 44 10-11-month-olds (an age with high variability in early speech sound production), this study tests whether infants' early consonant productions match words and objects in their environment. We find that infants' babble matches the consonants produced in their caregivers' speech. Infants with a well-established consonant repertoire also match their babble to objects in their environment. Our findings show that infants' early consonant productions are shaped by their input: by 10 months, the sounds of babble match what infants see and hear.