Phonotactic Probability and Neighborhood Density on Word Learning by Preschool Children (Storkel et al., 2013)

Purpose Phonotactic probability or neighborhood density has predominately been defined through the use of gross distinctions (i.e., low vs. high). In the current studies, the authors examined the influence of finer changes in probability (Experiment 1) and density (Experiment 2) on word learning. Method The authors examined the full range of probability or density by sampling 5 nonwords from each of 4 quartiles. Three- and 5-year-old children received training on nonword–nonobject pairs. Learning was measured in a picture-naming task immediately following training and 1 week after training. Results were analyzed through the use of multilevel modeling. Results A linear spline model best captured nonlinearities in phonotactic probability. Specifically, word learning improved as probability increased in the lowest quartile, worsened as probability increased in the mid-low quartile, and then remained stable and poor in the 2 highest quartiles. An ordinary linear model sufficiently described neighborhood density. Here, word learning improved as density increased across all quartiles. Conclusion Given these different patterns, phonotactic probability and neighborhood density appear to influence different word learning processes. Specifically, phonotactic probability may affect recognition that a sound sequence is an acceptable word in the language and is a novel word for the child, whereas neighborhood density may influence creation of a new representation in long-term memory.语音配列概率（phonotactic probability）与邻域密度（neighborhood density）的定义长期以来主要通过粗粒度区分（即高与低两类）来确立。在本系列研究中，作者考察了概率（实验1）与密度（实验2）的细粒度变化对单词学习的影响。 方法 作者通过从4个四分位数区间中各采样5个非词，覆盖了概率或密度的全部取值范围。研究招募3岁与5岁儿童，对其开展非词-非物体配对训练。分别在训练后即刻及训练1周后，通过图片命名任务评估单词学习效果。研究采用多层建模方法对实验结果进行分析。 结果 线性样条模型（linear spline model）最能拟合语音配列概率的非线性变化特征。具体而言，单词学习表现在最低四分位数区间内随概率提升而改善，在中低四分位数区间内随概率提升而下降，而在最高两个四分位数区间内则保持稳定且处于较低水平。普通线性模型则足以描述邻域密度的变化规律：在所有四分位数区间内，单词学习表现均随密度提升而改善。 结论 基于上述不同的变化模式，语音配列概率与邻域密度似乎通过不同的机制影响单词学习过程。具体而言，语音配列概率可能影响个体对某一声音序列是否属于该语言的合法单词、且对儿童而言为新异词汇的识别过程；而邻域密度则可能影响长时记忆中新的词汇表征的构建过程。