Initial noun meanings do not differentiate into object categories: An experimental approach to Werner and Kaplan's hypothesis

Large-scale data decipher children's scale errors: A meta-analytic approach using the zero-inflated Poisson models

Scale errors are intriguing phenomena in which a child tries to perform an object-specific action on a tiny object. Several viewpoints explaining the developmental mechanisms underlying scale errors exist; however, there is no unified account of how different factors interact and affect scale errors, and the statistical approaches used in the previous research do not adequately capture the structure of the data. By conducting a secondary analysis of aggregated datasets across nine different studies (n = 528) and using more appropriate statistical methods, this study provides a more accurate description of the development of scale errors. We implemented the zero-inflated Poisson (ZIP) regression that could directly handle the count data with a stack of zero observations and regarded developmental indices as continuous variables. The results suggested that the developmental trend of scale errors was well documented by an inverted U-shaped curve rather than a simple linear function, although nonlinearity captured different aspects of the scale errors between the laboratory and classroom data. We also found that repeated experiences with scale error tasks reduced the number of scale errors, whereas girls made more scale errors than boys. Furthermore, a model comparison approach revealed that predicate vocabulary size (e.g., adjectives or verbs), predicted developmental changes in scale errors better than noun vocabulary size, particularly in terms of the presence or absence of scale errors. The application of the ZIP model enables researchers to discern how different factors affect scale error production, thereby providing new insights into demystifying the mechanisms underlying these phenomena. A video abstract of this article can be viewed at https://youtu.be/1v1U6CjDZ1Q RESEARCH HIGHLIGHTS: We fit a large dataset by aggregating the existing scale error data to the zero-inflated Poisson (ZIP) model. Scale errors peaked along the different developmental indices, but the underlying statistical structure differed between the in-lab and classroom datasets. Repeated experiences with scale error tasks and the children's gender affected the number of scale errors produced per session. Predicate vocabulary size (e.g., adjectives or verbs) better predicts developmental changes in scale errors than noun vocabulary size.

When "shoe" becomes free from "putting on": The link between early meanings of object words and object-specific actions

Nouns referring to objects dominate children's early vocabulary over verbs referring to actions. However, some scholars have argued that early object-word meanings cannot be easily classified into specific object categories; rather, they have much undifferentiated meanings in which both objects and their specific actions are intertwined. We experimentally investigated this view using a two-alternative forced-choice task involving toddlers aged 18-23 months (n = 69). Both the cross-sectional and longitudinal results suggested that unlike older toddlers, younger ones could not select the correct referents when objects and object-specific actions were presented separately (e.g., "doing a filler action with shoes" vs. "putting on filler objects as if they were shoes") despite being successful when both were matched (e.g., "putting shoes on" vs. "doing a filler action with filler objects"). Additionally, toddlers failed to judge object-word referents solely by object-specific actions. These results indicated that early object-word meanings constitute the undifferentiated fusion of both objects and actions, and they subsequently differentiate into specific object categories independent of actions. Furthermore, the extent of such semantic differentiation is associated with the vocabulary growth of action words, suggesting that object-word meaning differentiation encouraged toddlers to develop new labels that could distinguish specific actions from objects. These findings revealed the uniqueness of young children's object-word comprehension, which is different from that of adults.

Looking represents choosing in toddlers: Exploring the equivalence between multimodal measures in forced-choice tasks

In the two-alternative forced-choice (2AFC) paradigm, manual responses such as pointing have been widely used as measures to estimate cognitive abilities. While pointing measurements can be easily collected, coded, analyzed, and interpreted, absent responses are often observed particularly when adopting these measures for toddler studies, which leads to an increase of missing data. Although looking responses such as preferential looking can be available as alternative measures in such cases, it is unknown how well looking measurements can be interpreted as equivalent to manual ones. This study aimed to answer this question by investigating how accurately pointing responses (i.e., left or right) could be predicted from concurrent preferential looking. Using pre-existing videos of toddlers aged 18-23 months engaged in an intermodal word comprehension task, we developed models predicting manual from looking responses. Results showed substantial prediction accuracy for both the Simple Majority Vote and Machine Learning-Based classifiers, which indicates that looking responses would be reasonable alternative measures of manual ones. However, the further exploratory analysis revealed that when applying the created models for data of toddlers who did not produce clear pointing responses, the estimation agreement of missing pointing between the models and the human coders slightly dropped. This indicates that looking responses without pointing were qualitatively different from those with pointing. Bridging two measurements in forced-choice tasks would help researchers avoid wasting collected data due to the absence of manual responses and interpret results from different modalities comprehensively.