Six-month-olds infer object size based on pitch: they map high-pitched vowels onto smaller objects and low-pitched vowels onto larger objects (Peña et al., 2011). The ‘sound symbolism bootstrapping hypothesis’ (Imai & Kita, 2014) proposes that this may support understanding of word-meaning correspondences; by drawing on iconic pairings between linguistic cues and corresponding referents (e.g., higher pitch for smaller objects), infants develop understanding of word-referent associations. Here we analyse mother-child interactions, testing whether sound-symbolic pitch-size correspondences occur in infant-directed speech. 40 dyads engaged in (semi-)naturalistic interaction around picture books containing images of toys of varying sizes. We compare mothers’ pitch when referring to small versus large toys, analysing i) actual size (bigger vs. smaller toys); ii) relative toy size congruence (i.e., congruent vs. incongruent with real-world expectation); and iii) transparency of the test paradigm as regards its focus on size contrastiveness (non-transparent, moderately transparent, highly transparent) to observe the nuances of size sound symbolism in infant-directed speech.

Variegation – the presence of more than one supraglottal consonant per word – is a key challenge for children as they increase their expressive vocabulary toward the end of the single-word period. Here we consider the prosodic structures of target words and child forms in English, Finnish, French, Japanese and Mandarin to determine whether children learning these languages respond similarly to the challenge or instead differ in ways related to the phonological structure of the adult language. Based on proportional occurrence of each structure, we find that the word forms of children learning Mandarin and Japanese show more variegation than do those of children learning the European languages, although their target words do not; proportions of reduplication, consonant harmony and single-consonant words also differ by language. We conclude that experience with the structure of the language – and thus representation, as well as immature articulatory skills – shapes children’s responses to variegation.

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.

Previous studies have shown that by 11 but not by 10 months infants recognize words that have become familiar from everyday life independently of the experimental setting. This study explored the ability of 10-, 11-, and 12-month-old infants to recognize familiar words in sentential context, without experimental training. The headturn preference procedure was used to contrast passages containing words likely to be familiar to the infants with passages containing words unlikely to have been previously heard. Two stimulus words were inserted near the beginning and end of each of a set of simple sentence frames. The ability to recognize the familiar words within sentences emerged only at 12 months of age. The contrast between segmentation abilities as they emerge as a result of everyday exposure to language, as assessed here, and those abilities as measured in studies in which words are experimentally trained is discussed in terms of memory-based mechanisms.