From gestures to words: understanding variability in early communicative skills across different populations

Within a constructivist framework, this dissertation aimed to examine how gesture production is influenced by multiple sources of variability and how it, in turn, contributes to individual differences in linguistic skills. Across four cross-sectional studies, three cases (preterm birth, cultural background, late talkers) were analyzed to capture complementary forms of developmental variability. Chapter 2 presents a study comparing communicative, cognitive, motor, and linguistic skills in 18-month-old Italian preterm and full-term infants, showing fewer index-finger points, lower cognitive, motor, and linguistic skills, with strong associations among pointing and cognitive, and motor skills, in preterm than to full term infants. Chapter 3 presents two studies: Study 1 extended analysis on preterm birth by including caregivers’ behaviors, revealing no group differences in both communicative input and responsiveness; Study 2 compared Italian and German dyads, showing no group differences in infants’ pointing, but fewer words and more unimodal gestures in Italian than German infants. Italian caregivers produced more pointing, more but shorter utterances, and more semantically contingent responses to infants’ unimodal gestures than German caregivers. Across both studies, caregivers’ semantically contingent responses were more frequent following infants’ pointing, particularly bimodal, then vocal productions. Chapter 4 presents a study comparing communicative-linguistic skills in 24-month-old German late talkers and typically developing peers, during a picture naming task, showing more unimodal gestural, but fewer spoken and bimodal responses in late talkers than typically developing peers. Across the sample, iconic gestures correlated negatively with lexical accuracy. Chapter 5 presents a study comparing communicative-linguistic skills in 30-month-old Italian receptive/expressive and expressive late talkers during a picture naming task, showing lower lexical scores, fewer unimodal spoken, bimodal responses, and representational gestures in receptive–expressive than expressive late talkers. Together, findings highlight gestures as key behavioral markers reflecting and shaping variability in early communicative skills across neurobiological and cultural conditions.