Working memory development from early childhood to adolescence using two nationally representative samples.

May combine two claims.

In the full-age PSID-CDS data, for Forward Digit Span, the cubic functional form was the best-fitting model for boys and girls, but the cubic coefficient was not statistically significant for boys after multiple-comparison adjustment.

“For the Forward Digit Span, the cubic functional form was the best fitting model for boys and for girls. However, the cubic coefficient was not statistically significant for boys after adjusting for multiple comparisons (girls: b = 0.002, p < .001; boys: b = 0.001, p = .005).”

May combine two claims.

The study observed non-linear growth patterns for both forward and backward digit span tasks from 3 to 19 years of age, with the most rapid growth in childhood followed by a brief acceleration in early adolescence.

“First, we observed non-linear growth patterns for both forward and backward digit span tasks from 3 to 19 years of age, with the most rapid growth occurring across childhood, followed by a brief accelerated period of growth during early adolescence.”

May combine two claims.

Working memory capacity showed rapid age-related changes across childhood and to a lesser degree during early adolescence, with two periods of relative calm: late childhood and late adolescence.

“Specifically, we observed rapid age-related changes in WM capacity across childhood and to a lesser degree during early adolescence, and two periods of relative calm: late childhood and late adolescence.”

Probably not a substantial claim: may not pass S3 (load-bearing).

In the full PSID-CDS data, the sex-by-age interaction was not statistically significant for the cubic functional form of Backward Digit Span.

“and Backward Digit Span (b = 0.001, SE = .001, p = .224; see Figure 3) in the full PSID-CDS dataset.”

May combine two claims.

The age of onset differed for forward and backward span tasks: children as young as 3 years could complete the forward span task, while backward span performance did not emerge until age 5.

“Second, the age of onset differed for forward and backward span tasks–children as young as 3 years of age were able to complete the forward span task, whereas performance on backward span did not emerge until 5 years of age.”

May combine two claims.

In the age-restricted PSID-CDS data, the best-fitting growth model was quadratic rather than cubic, because the cubic coefficient was not statistically significant.

“Although inspection of the model fit indices in the age-restricted PSID-CDS data suggested that a cubic functional form best fit the data, the cubic coefficient was non-significant (b = 0.015, p = .208).”

• Also stated in: § Results · plain

  “Therefore, the best fitting model was the quadratic functional form, which had the next-lowest model fit indices and a statistically significant growth coefficient (AIC =104487838; BIC =104487868; b =−0.101, p <.001).”

May combine two claims.

In the full-age PSID-CDS data, for Backward Digit Span, the cubic functional form was the best-fitting model for boys and girls, but the cubic coefficient was not statistically significant for boys after multiple-comparison adjustment.

“For the Backward Digit Span, the cubic functional form was the best fit model for boys and for girls. However, the cubic coefficient was not statistically significant for boys after adjusting for multiple comparisons (girls: b = .002, p < .001; boys: b = .001, p = .035).”

May combine two claims.

In the restricted-age PSID-CDS data, the best-fitting model for boys and girls was quadratic, with statistically significant growth coefficients.

“Therefore, the best fitting model for boys and girls was the quadratic functional form, which had the next-least model fit indices and statistically significant growth coefficients (girls: b = −0.116, p < .001; boys: b = −0.087, p < .001).”

Probably not a substantial claim: may not pass S3 (load-bearing).

In the ECLS-K:2011 data, the sex-by-age interaction was not statistically significant for the logarithmic functional form of Numbers Reversed after multiple-comparison correction.

“and the logarithmic functional form of Numbers Reversed in the ECLS-K:2011 (b = −0.520, SE = .250, p = .041; see Figure 3) after the multiple comparison correction.”

Probably not a substantial claim: may not pass S3 (load-bearing).

In the restricted PSID-CDS data, the sex-by-age interaction was not statistically significant for the cubic functional form of Backward Digit Span.

“We also observed non-significant interaction coefficients (i.e., child ages 6–11) for the cubic functional form of Backward Digit Span (b = −0.029, SE = .033, p = .372; see Figure 3) in the restricted PSID-CDS dataset”

May combine two claims.

In the ECLS-K:2011 data, 15% of the variability in Numbers Reversed was between individuals and 85% was within person.

“In the ECLS-K:2011 data, the ICC suggested that 15% of the variability in number reversed can be attributed to differences between individuals, with 85% of the variability being attributed to differences within person.”

May combine two claims.

Subgroup analyses indicated that males and females developed working memory at similar rates across the population, with no meaningful sex differences in overall functional form or rate of growth.

“Finally, results from subgroup analyses indicated that males and females developed WM at similar rates across the population.”

• Also stated in: § Discussion · plain

  “A notable finding that emerged from these analyses is the lack of meaningful sex differences in the overall functional form and rate of growth of WM.”

Classified as probably not a substantial claim.

Missing data in the ECLS-K:2011 were imputed using multiple imputations by chained equations to create 40 complete data sets to account for longitudinal attrition and planned missingness.

“To account for longitudinal attrition and planned missingness across the study’s waves, missing data were imputed using multiple imputations (MI; Rubin, 1987) by chained equations procedures implemented in STATA (StataCorp., 2019) to create 40 complete data sets.”

• cites Rubin, 1987Not checked yet

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Probably not a substantial claim: may not pass S3 (load-bearing).

The 1997 cross-sectional family weight was applied to make the PSID-CDS sample representative of the U.S. population during 1997.

“The 1997 cross-sectional family weight was applied to make the sample representative of the U.S. population during 1997.”

Probably not a substantial claim: may not pass S3 (load-bearing).

Baseline sampling weights provided by NCES were applied to make the ECLS-K:2011 sample representative of the U.S. population during the 2010-2011 school year.

“The baseline sampling weights provided by NCES were applied to make the sample representative of the U.S. population during the 2010–2011 school year.”

Classified as probably not a substantial claim.

Missing data for digit span variables in the PSID-CDS were imputed using multiple imputations by chained equations to create 70 complete data sets.

“To account for the high levels of missingness, missing data were imputed using multiple imputations (Rubin, 1987) by chained equations procedures implemented in Stata (StataCorp., 2019) to create 70 complete data sets.”

• cites Rubin, 1987Not checked yet

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Classified as probably not a substantial claim.

Variables related to missingness on the outcome variables were entered in the PSID-CDS imputation models as covariates to adhere to MAR assumptions.

“Variables that were related to missingness on the outcome variables of interest were entered in our imputation models as covariates to adhere to MAR assumptions (Enders, 2010).”

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• AssumptionThe authors state this as an assumption: Missing data on digit span variables are missing at random conditional on the covariates included in the imputation models.

Probably not a substantial claim: may not pass S3 (load-bearing). May combine two claims.

The Digit Span Task from the WISC-R demonstrates excellent reliability (α = .93) and good test-retest reliability (r = .73).

“The Digit Span Task demonstrates excellent reliability (α = .93; Wechsler, 2008) and good test-retest reliability (r = .73; Lipsey et al., 2017).”

• cites Wechsler, 2008Not checked yet

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• cites Lipsey et al., 2017Not checked yet

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May combine two claims.

When sex disparities in working memory emerge, they depend on the developmental stage of assessment and are almost always examined cross-sectionally.

“When disparities emerge, they depend on the developmental stage of assessment and are almost always examined cross-sectionally.”

Probably not a substantial claim: may not pass S3 (load-bearing).

The study analyses were preregistered on OSF.

“All study analyses were preregistered on OSF: https://osf.io/szvmx/ (Ellis et al., 2021).”

• cites Ellis et al., 2021Not checked yet

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Classified as probably not a substantial claim.

For time-unstructured or unequally spaced time variables, mixed-effects modeling is preferred over latent growth-curve modeling.

“When dealing with an independent variable that is time-unstructured (such as child age in the PSID-CDS), or when dealing with a time variable that has unequal distances (as in the ECLS-K:2011), mixed effects modeling is preferred over other methods, such as latent growth-curve modeling (McNeish & Matta, 2018).”

• cites McNeish & Matta, 2018Not checked yet

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Probably not a substantial claim: may not pass S3 (load-bearing).

Contextual and biological changes during early adolescence, such as puberty, neural differentiation, and educational and social transitions, might explain the acceleration in working memory development.

“Like childhood, there are also contextual and biological changes occurring during this time that might explain this acceleration in WM development, such as the onset and progression of puberty, adolescent neural differentiation, and transitions in educational and social contexts, which have been shown to influence the maturation of executive systems (see Blakemore, & Choudhury, 2006, for review).”

• cites Blakemore, & Choudhury, 2006Not checked yet

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Classified as probably not a substantial claim.

Variables significantly related to the outcome of interest were entered in the ECLS-K:2011 imputation models as covariates to adhere to MAR assumptions.

“Further, and to adhere to MAR assumptions, variables significantly related to the outcome of interest were entered in our imputation models as covariates (Enders, 2010).”

• cites Enders, 2010Not checked yet

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• AssumptionThe authors state this as an assumption: Missing data on digit span variables are missing at random conditional on the covariates included in the imputation models.

Classified as probably not a substantial claim. May combine two claims.

There is evidence supporting a male advantage in visuospatial working memory, small and first appearing during adolescence.

“Conversely, there is also evidence supporting a male advantage in visuospatial WM; however, these sex differences are small and first appear during adolescence (Voyer, 2016).”

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May combine two claims.

Both PSID-CDS and ECLS-K:2011 include counting span tasks measured multiple times, making it possible to examine developmental trends and compare findings across datasets.

“Both the PSID-CDS and the ECLS-K:2011 include counting span tasks measured multiple times across the studies, making it possible to examine developmental trends and compare findings across the two data sets.”

• AssumptionRests on an assumption: The digit span measures in PSID-CDS and ECLS-K:2011 assess the same verbal working memory construct comparably enough to compare developmental trends.

Probably not a substantial claim: may not pass S3 (load-bearing). May combine two claims.

Forward span includes storage and maintenance components, whereas backward span also requires manipulation and updating of stored information.

“Forward span includes storage and maintenance components, whereas backward span also requires participants to manipulate and update the information stored in short-term memory, and is often described as capturing working memory capacity because of the additional processing demand (Conway et al., 2005; Cowan, 2008).”

• cites Conway et al., 2005Not checked yet

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• cites Cowan, 2008Not checked yet

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Classified as probably not a substantial claim. May combine two claims.

W-scores are an equal-interval score metric sensitive to longitudinal change.

“W-scores, a score metric on an equal-interval scale sensitive to longitudinal change, were used for the present study (Mather & Jaffe, 2016; McGrew & Woodcock, 2001).”

• cites Mather & Jaffe, 2016Not checked yet

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• cites McGrew & Woodcock, 2001Not checked yet

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May combine two claims.

Both PSID-CDS and ECLS-K:2011 are nationally representative, making them ideal to examine whether developmental trajectories differ across biological sex.

“Finally, both the PSID-CDS and ECLS-K:2011 are nationally-representative, making them ideal to examine whether developmental trajectories differ across biological sex, which can provide patterns of normative WM development generalizable to the U.S. population.”

May combine two claims.

Meta-analyses indicate a small but significant female advantage in auditory working memory in children and adolescents, but not during adulthood.

“For example, meta-analyses indicate a small, but significant female advantage in auditory WM in children and adolescents, but not during adulthood (Lynn & Irwing, 2008).”

• cites Lynn & Irwing, 2008Not checked yet

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Probably not a substantial claim: may not pass S3 (load-bearing).

Differences in the scaling of counting span across the two datasets warrant caution in directly comparing results between PSID-CDS and ECLS-K:2011.

“However, the difference in scaling of counting span across the two data sets warrants caution in directly comparing the results across the PSID-CDS and ECLS-K:2011.”

May combine two claims.

When modeled at the population level, working memory sex differences are minimal at any given developmental stage and disappear when growth patterns over time are examined.

“Although prior research in this area has been mixed (Lynn & Irwing, 2008; Voyer, 2016), our findings suggest that when modeled at the population level, WM sex differences are minimal at any given developmental stage and entirely disappear when examining growth patterns over time.”

• cites Lynn & Irwing, 2008Not checked yet

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• cites Voyer, 2016Not checked yet

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May combine two claims.

Sex differences in working memory are generally small, domain-specific, and vary across age.

“Sex differences in WM are generally small, domain-specific, and vary across age.”

May combine two claims.

Rapid working memory development during childhood coincides with physical and neurological changes and with contextual transitions that have been shown to influence executive-system maturation.

“The rapid development of WM during childhood also coincides with the dramatic physical and neurological changes that take place during childhood, as well as with important contextual transitions (e.g., start of formal schooling) that have been shown to influence the maturation of executive systems (Kim et al., 2021; Finch, 2019).”

• cites Kim et al., 2021Not checked yet

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• cites Finch, 2019Not checked yet

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May combine two claims.

In the PSID-CDS, missing data for forward digit span ranged from 26.25% to 63.64% and for backward span from 26.36% to 62.61%.

“Missing data for digit span forward ranged from 26.25% to 63.64% and for backward span from 26.36% to 62.61% (Table 1 displays missing rates for all study variables).”

Probably not a substantial claim: may not pass S3 (load-bearing). May combine two claims.

A Bonferroni correction was used to adjust for multiple testing, with only p-values below .001 considered statistically significant.

“To adjust for multiple testing, we used a Bonferroni correction, such that only p-values < .001 were considered statistically significant.”

May combine two claims.

The pattern of working memory growth highlights the relative importance of early childhood for normative working memory development and may indicate a window when interventions are most effective.

“This pattern of WM growth highlights the relative importance of the early childhood period for normative WM development, which may provide a window of opportunity during which the effects of interventions might be the most effective.”

Probably not a substantial claim: may not pass S3 (load-bearing). May combine two claims.

The study focused solely on verbal working memory development, and the extent to which the developmental trends extend to visuospatial working memory remains unclear.

“First, this study focused solely on verbal WM development - however, the extent to which these developmental trends extend to visuospatial WM development remains unclear.”

Probably not a substantial claim: may not pass S3 (load-bearing). May combine two claims.

Although the findings are representative of the U.S. population, they are generalizable only to a small fraction of the human population.

“Finally, although these findings are representative of the U.S. population, they are only generalizable to a small fraction of the human population.”

• AssumptionRests on an assumption: The PSID-CDS and ECLS-K:2011 samples are representative of the U.S. population.

May combine two claims.

The findings offer information about normative working memory development at the population level and can provide researchers a foundation for understanding intervention effects independent of normative age-related changes.

“Not only do these findings offer information about normative development of working memory at the population level, they can also provide researchers with a foundation to understand the effects of interventions independent of normative age-related changes in working memory.”

• AssumptionRests on an assumption: The PSID-CDS and ECLS-K:2011 samples are representative of the U.S. population.

Probably not a substantial claim: may not pass S3 (load-bearing).

It is possible that task performance is not increasing as quickly as true working memory capacity over time.

“As a result, it is possible that task performance is not increasing as quickly as true WM capacity over time.”