The conclusions reached by Leibovich et al. urge the field to regroup and consider new ways of conceptualizing quantitative development. We suggest three potential directions for new research that follow from the authors' extensive review, as well as building on the common ground we can take from decades of research in this area.

We designed a parent-directed home-visiting intervention targeting socioeconomic status (SES) disparities in children's early language environments. A randomized controlled trial was used to evaluate whether the intervention improved parents' knowledge of child language development and increased the amount and diversity of parent talk. Twenty-three mother–child dyads (12 experimental, 11 control, aged 1;5–3;0) participated in eight weekly hour-long home-visits. In the experimental group, but not the control group, parent knowledge of language development increased significantly one week and four months after the intervention. In lab-based observations, parent word types and tokens and child word types increased significantly one week, but not four months, post-intervention. In home-based observations, adult word tokens, conversational turn counts, and child vocalization counts increased significantly during the intervention, but not post-intervention. The results demonstrate the malleability of child-directed language behaviors and knowledge of child language development among low-SES parents.

Speakers of all ages spontaneously gesture as they talk. These gestures predict children's milestones in vocabulary and sentence structure. We ask whether gesture serves a similar role in the development of narrative skill. Children were asked to retell a story conveyed in a wordless cartoon at age five and then again at six, seven, and eight. Children's narrative structure in speech improved across these ages. At age five, many of the children expressed a character's viewpoint in gesture, and these children were more likely to tell better-structured stories at the later ages than children who did not produce character-viewpoint gestures at age five. In contrast, framing narratives from a character's perspective in speech at age five did not predict later narrative structure in speech. Gesture thus continues to act as a harbinger of change even as it assumes new roles in relation to discourse.

Children with pre/perinatal unilateral brain lesions (PL) show remarkable plasticity for language development. Is this plasticity characterized by the same developmental trajectory that characterizes typically developing (TD) children, with gesture leading the way into speech? We explored this question, comparing eleven children with PL – matched to thirty TD children on expressive vocabulary – in the second year of life. Children with PL showed similarities to TD children for simple but not complex sentence types. Children with PL produced simple sentences across gesture and speech several months before producing them entirely in speech, exhibiting parallel delays in both gesture + speech and speech-alone. However, unlike TD children, children with PL produced complex sentence types first in speech-alone. Overall, the gesture–speech system appears to be a robust feature of language learning for simple – but not complex – sentence constructions, acting as a harbinger of change in language development even when that language is developing in an injured brain.

The talk children hear from their primary caregivers predicts the size of their vocabularies. But children who spend time with multiple individuals also hear talk that others direct to them, as well as talk not directed to them at all. We investigated the effect of linguistic input on vocabulary acquisition in children who routinely spent time with one vs. multiple individuals. For all children, the number of words primary caregivers directed to them at age 2 ; 6 predicted vocabulary size at age 3 ; 6. For children who spent time with multiple individuals, child-directed words from all household members also predicted later vocabulary and accounted for more variance in vocabulary than words from primary caregivers alone. Interestingly, overheard words added no predictive value to the model. These findings suggest that speech directed to children is important for early word learning, even in households where a sizable proportion of input comes from overheard speech.

This study examined the relation between young English language learners’ (ELL) native oral language skills and their language input in transitional bilingual education kindergarten classrooms. Spanish-speaking ELLs’ (n = 101) Spanish expressive language skills were assessed using the memory for sentences and picture vocabulary subtests of the Woodcock Language Proficiency Battery—Revised. Samples of transitional bilingual education teachers’ (n = 21) speech were recorded and coded for syntactic complexity and vocabulary usage. Results revealed considerable variation in ELLs’ language scores, with overall performance below the normative sample. There was also wide variation in teachers’ speech across classrooms. Hierarchical linear modeling revealed that gains in ELLs’ expressive language skills were positively related to the diversity of teachers’ vocabulary and teachers’ syntactic complexity. These findings suggest that the quality of teachers’ language input, not just the quantity of their input, plays a significant role in the language learning trajectories of ELLs.

The proposal of Rips et al. is motivated by discontinuity and input claims. The discontinuity claim is that no continuity exists between early (nonverbal) numerical representations and natural number. The input claim is that particular experiences (e.g., cardinality-related talk and object-based activities) do not aid in natural number construction. We discuss reasons to doubt both claims in their strongest forms.

Thomas & Karmiloff-Smith (T&K-S) show that the assumption of residual normality (RN) does not hold in connectionist simulations, and argue that RN has been inappropriately applied to childhood disorders. We agree. However, we suggest that the RN hypothesis may never have been fully viable, either empirically or computationally.