Table 2.
Pearson correlations between the study variables, and descriptive statistics and test scores (means and standard deviations) of the total sample (n = 80)
| Age (yr) a | Sex (% girls) | SES a | Grade (% grade 3) | Low VSWM load trials (% correct)a | High VSWM load trials (% correct)a | All VSWM trials (% correct)a | Gross motor skills (factor score)a | Cardiovascular fitness (stages)a | |
|---|---|---|---|---|---|---|---|---|---|
| Age (yr)a | 1 | ||||||||
| Sex (% girls) | -0.046 | 1 | |||||||
| SESa | -0.081 | 0.022 | 1 | ||||||
| Grade (% grade 3) | 0.796** | 0.074 | 0.056 | 1 | |||||
| Low VSWM load trials (% correct)a | 0.048 | -0.061 | 0.207 | 0.160 | 1 | ||||
| High VSWM load trials (% correct)a | -0.035 | 0.025 | 0.224* | 0.093 | 0.750** | 1 | |||
| All VSWM trials (% correct)a | 0.008 | -0.020 | 0.23* | 0.136 | 0.937** | 0.934** | 1 | ||
| Gross motor skills (factor score)a | 0.268* | -0.057 | 0.020 | 0.306** | 0.364** | 0.236* | 0.322** | 1 | |
| Cardiovascular fitness (stages)a | 0.198 | -0.257* | 0.154 | 0.142 | 0.279* | 0.221* | 0.268* | 0.494** | 1 |
| Mean (SD) or percentage | 9.17 (0.62) | 51.30 | 4.58 (1.06) | 47.50 | 70.70 (15.97) | 66.00 (15.54) | 68.35 (14.74) | 0.18 (1.01) | 4.74 (1.91) |
Note. Performance on low and high working memory significantly differed as measured with a paired sample t-test, t (80) = 4.245, p < 0.001; SES = socioeconomic status, obtained by a parental questionnaire. Level of parental education of both parents was requested and varied from 0 (no education) to 7 (postdoctoral education; Schaart, Mies, & Westerman, 2008). Average education level of both parents was used as a measure of SES. If the level of parental education was specified for only one of the parents, this level was used as a measure of SES for the child
aMean (SD); * p < 0.05; ** p < 0.01