Why preschool experience matters

Here, I present two recent articles focusing on the importance of language in preschoolers. First, Perry, Kucker, Hurst & Samuelson (2022) published “Late Bloomer or Language Disorder? Differences in toddler vocabulary composition associated with long-term language outcomes” in Child Development. Here’s the slightly edited abstract and highlights:

Children with delays in expressive language (late talkers) have heterogeneous developmental trajectories. Some are late bloomers who eventually “catch-up,” but others have persisting delays or are later diagnosed with developmental language disorder (DLD). Early in development it is unclear which children will belong to which group. We compare the toddler vocabulary composition of late talkers with different long-term outcomes. The literature suggests most children with typical development (TD) have vocabularies dominated by names for categories organized by similarity in shape (e.g., cup), which supports a bias to attend to shape when generalizing names of novel nouns—a bias associated with accelerated vocabulary development. Previous work has shown that as a group, late talkers tend to say fewer names for categories organized by shape and are less likely to show a “shape bias” than TD children. Here, in a retrospective analysis of 850 children, we compared the vocabulary composition of groups of toddlers who were late bloomers or persisting late talkers. At Time 1 (13-27 months), the persisting late talkers said a smaller proportion of shape-based nouns than both TD children and late bloomers who “caught up” to typically sized vocabularies months later (18-38-months). Additionally, children who received a DLD diagnosis between 4 and 7 years said a significantly smaller proportion of shape-based nouns in year two than TD children and children with other diagnoses (e.g., dyslexia). These findings bring new insight into sources of heterogeneity amongst late talkers and offer a new metric for assessing risk.

Toddler vocabulary composition, including the proportion of names for categories organized by shape, like spoon, was used to retrospectively compare outcomes of late talking children. Persisting Late Talkers said a smaller proportion of shape-based nouns during toddlerhood relative to Late Bloomers (late talkers who later caught up to have typically-sized vocabularies). Children with later DLD diagnoses said a smaller proportion of shape-based nouns during toddlerhood relative to children without a DLD diagnosis. The data illustrate the cascading effects of vocabulary composition on subsequent language development and suggest vocabulary composition may be one important marker of persisting delays

I love this study because it suggests questions to ask when children in early elementary school are struggling. I was unaware of the importance of shape-based nouns and think it intriguing that they have a cascading effect. While the second study looks at math abilities, it is similarly surprising in emphasizing language. James-Brabham, Loveridge, Sella, Wakeling, Carroll & Blakey (2023) published “How do Socioeconomic Attainment Gaps in Early Mathematical Ability Arise?” in Child Development. Here’s the highly edited abstract and article:

Socioeconomic attainment gaps in mathematical ability are evident before children begin school, and widen over time. Little is known about why early attainment gaps emerge. Two cross-sectional correlational studies were conducted in 2018–2019 with socioeconomically diverse preschoolers, to explore four factors that might explain why attainment gaps arise: working memory, inhibitory control, verbal ability, and frequency of home mathematical activities (N = 304, 54% female; 84% White, 10% Asian, 1% black African, 1% Kurdish, 4% mixed ethnicity). Inhibitory control and verbal ability emerged as indirect factors in the relation between socioeconomic status and mathematical ability, but neither working memory nor home activities did. We discuss the implications this has for future research to understand, and work towards narrowing attainment gaps.

The development of early mathematical skills is of great importance—not simply for building more advanced mathematical skills, but also because it is a strong predictor of overall academic attainment. Poor mathematical skills have consequences far beyond academic attainment, including negative associations with health, income, and quality of life. There are large individual differences in mathematical ability, and one factor which predicts these differences is socioeconomic status (SES), for example, maternal education at age four predicts mathematical achievement at age 15. 

Working memory is the first proposed factor by which SES disparities in early mathematics may develop. Working memory is a core cognitive ability that enables us to maintain and manipulate information. Working memory may support early mathematics by enabling children to retrieve numerical facts, and to maintain and process numerical information to successfully carry out mathematical operations. 

Inhibitory control is the second proposed factor by which SES disparities in early mathematics may develop. Inhibitory control enables us to suppress distractions and resist prepotent but incorrect responses. Inhibitory control may support early mathematical skills by helping children to ignore distracting information while focusing on a mathematical problem, and helping them to suppress prepotent but incorrect strategies when solving a problem. 

Verbal ability is the third proposed factor by which SES differences in early mathematical ability may develop. Socioeconomic disparities in verbal ability are well documented: from as young as 18 months of age, children from lower-SES households have significantly fewer words in their vocabulary than children from higher-SES households (Fernald et al., 2013). 

Home mathematical activities are the fourth factor by which socioeconomic attainment gaps in early mathematical ability may develop. In recent years, there has been an increased focus on the role of the home environment in the development of mathematical skills, focusing on the frequency of the mathematical activities that parents do with their children in the home. 

Four key findings emerged from this research. Firstly, there was a clear SES attainment gap in early mathematical ability. Secondly, verbal ability indirectly predicted the relation between SES and early mathematical ability. Thirdly, inhibitory control indirectly predicted the relation between SES and mathematical ability. Fourthly, working memory and home mathematical activities did not explain SES disparities in mathematical ability in either study. The fact that both studies—with different samples and different measures of SES and home mathematical activities—align on all four key findings suggests these results are robust. We now discuss each of these findings in more detail.

The first key finding was that a SES attainment gap in mathematical ability is apparent in children as young as 3 years of age. This is striking, and demonstrates that there are factors at play before children start school that lead to inequalities in outcomes. We know that mathematical development proceeds cumulatively, meaning this early attainment gap is likely to not only remain, but to widen over time. This underlines the importance of targeting attempts to narrow this gap to the preschool years. 

The second key finding was that SES attainment gaps in early mathematics were indirectly explained by verbal ability. This is a key finding that bridges two important areas of research. Firstly, the finding that there are SES differences in verbal ability is consistent with a wealth of research demonstrating SES gradients in verbal ability. Secondly, the findings are also consistent with a separate, growing body of evidence demonstrating the importance of verbal ability in the development of mathematical skills. Verbal ability may support mathematical skills in multiple ways. Notably, language is essential for attributing meaning to arbitrary mathematical concepts, and for expressing those meanings. It is also conceivable that verbal ability may modulate the cognitive demands of a task: for example, a child with poor verbal ability may not only have to meet the demands of the mathematical task itself, but also of learning, understanding and using unfamiliar language when completing the task. 

The third key finding was that SES attainment gaps in early mathematics were also indirectly explained by inhibitory control. This finding is consistent both with previous research showing inhibitory control to be important for early mathematical development, and with studies that have found SES gradients in inhibitory control. Specifically, SES disparities in mathematical skills may begin by SES influencing early verbal ability; this, in turn, may have a knock-on-effect on inhibitory control; which then goes on to influence mathematical ability. 

The fourth key finding was that SES attainment gaps in early mathematics were not explained by working memory or by home mathematical activities. Both studies showed that working memory was positively related to mathematical ability, but that working memory did not vary by SES. This suggests that despite working memory's importance for early mathematical skills, it may not be a mechanism that drives SES disparities in mathematics. 

Somewhat unexpectedly, both Studies 1 and 2 found that home mathematical activities did not relate to children's mathematical ability—and nor did they vary by SES. The absence of relation between frequency of home mathematical activities and mathematical ability is surprising, and worth further attention, not least because prior research on this topic has yielded contrasting results. One possible explanation could be the age of children: the current study was conducted with children prior to the start of formal education, in contrast to Lefevre et al.'s (2009) seminal study, which was conducted after children had begun formal education. It may be that the relation between home mathematical activities and mathematical ability is age-specific, with it emerging as children get older and are able to do more complex mathematical operations. Another possible explanation for the diversity in findings might be the socioeconomic features of the samples tested. The fact that both the present studies show this null relation, and that both use different home mathematical activities questionnaires, gives us confidence that in socioeconomically diverse samples, frequency of home mathematical activities does not influence mathematical ability prior to the start of formal education.

The present research is the first to directly investigate the specific factors that may explain SES gaps in early ability in a diverse socioeconomic sample. In two studies, we find that SES attainment gaps for mathematical ability are explained by both verbal ability and inhibitory control. We find that frequency of home mathematical activities does not vary by SES or influence early mathematical ability and it may be fruitful for future work to focus on the quality of these activities above and beyond frequency. By examining multiple factors, these studies indicate how early SES gaps in mathematical ability may arise. The findings offer a vital first step towards designing longitudinal studies to elucidate on the causal sequence and long-term consequences of these early inequalities.

I’ve written before about the importance of language in developing mathematics skills, but I find it fascinating that it is verbal ability and inhibitory control that better predict math abilities than working memory and math activities in the home. Like the first study, this one suggests good questions to ask and may have implications for intervention in lower SES communities.