Characteristics of included datasets from Peekbank.

“Admins” denotes separate experimental sessions. “CDIs” refers to whether the dataset contains parent report vocabulary data from the MacArthur-Bates Communicative Development Inventory.

Timecourse of word recognition at different ages.

The x-axis shows time (in ms) from the onset of the target label (vertical solid line). Colored lines show the average increase in proportion target looking post label onset at each age bin (in months). Age bins are larger for older children due to decreased data density. The dashed horizontal line represents chance looking. Error bands represent standard errors of the mean. Grey backgrounds highlight the short and long time windows used in subsequent analyses.

Participant-level target looking and reaction time (log), plotted by age (log).

Longitudinal datapoints are connected by lines. The solid blue line shows a linear fit and associated confidence interval. Thin colored lines show linear fits for those datasets spanning six or more months of age. The dashed line for accuracy shows chance-level looking (.5)

Participant-level variability in target looking and reaction time (log RT), plotted by age (log).

Plotting conventions are as in Figure 1.

Structural equation model showing the three-factor factor analysis with a regression of each latent variable on the logarithm of age.

Observed variables are notated as squares and latent variables are notated as circles Factor loadings and regression coefficients are shown with straight, solid lines; covariances are shown with dashed lines; residual variances are shown as solid circular connections. Stars show conventional levels of statistical significance, e.g. * indicates p < .05, ** indicates p < .01, and *** indicates p < .001. Covariances reflect age-residualized correlations between variables.

Growth curves from a logistic growth model showing predicted vocabulary growth for children with initial reaction times one SD faster than the mean (blue), at the mean (red), and one SD slower than the mean (green).

Individual longitudinal trajectories are shown in light gray. Solid lines show global model estimates and colored regions indicate 95% credible intervals.

Structural equation model showing longitudinal couplings between growth parameters.

Age distribution of unique participants for each dataset, using three-month bins.

Figure S2 shows the distribution of measurement intervals for longitudinal studies within the dataset.

Distribution of retest administrations across datasets with repeated measurements, colored by dataset.

Each count indicates a retest administration (initial administrations are excluded). Administrations listed with a retest interval of 0 indicate retests within a month of the initial administration.

Correlation between reaction times on all trials and reaction times on trials where the child pointed to the correct target.

Data from Creel (2024).

Goodness of fit for different distributional models for RT, split by age.

Distribution of RT overlaid with a log normal distribution, split by age.

Goodness of fit for different distributional models of accuracy, split by age.

Distribution of accuracies overlaid with normal distribution, split by age.

Pairwise correlations between primary variables of interest.

Model comparison metrics for different functional forms of the relationship between accuracy and age.

Model comparison metrics for different functional forms of the relationship between RT and age.

Goodness of fit comparison between different models of the relationship between age and RT.

Fixed effects coefficients for a model predicting log RT from both log age and linear age.

Factor loadings for the exploratory three factor solution using varimax rotation.

Parallel analysis scree plot showing the eigenvalues for each factor, for actual, simulated, and resampled data.

Comparison of confirmatory factor analysis models on longitudinal data or first administrations only.

Model comparison for alternative factor structures.

p-values show differences between adjacent models; no p-values are shown for comparisons between non-nested models.

Fixed effects estimates from logistic growth model.

Fixed effects estimates from logistic growth model using RT residualized on age as the predictor.

Growth curves from a logistic growth model showing predicted vocabulary growth for children based on their age-residualized initial reaction times.

Predictions are shown for children with initial reaction times one SD faster than the mean for their age (blue), at the mean for their age (red), and one SD slower than the mean for their age (green). Individual longitudinal trajectories are shown in light gray. Solid lines show global model estimates and colored regions indicate 95% credible intervals.

Fraction of data present for each measure at each time point for the longitudinal SEM.