Table 1.
Descriptive statistics for nappers (n = 27–43) and non-nappers (n = 37–60) within the younger half of the sample.
| Nappers | Non-nappers | Group differences | |||
|---|---|---|---|---|---|
| Mean | SD | Mean | SD | ||
| Age (years) | 4.619 | .575 | 5.355 | .721 | F(1,65) = 16.203, p < .001 |
| Source memory (% correct) | 13.83% | 15.55 | 15.95% | 15.62 | ns |
| 24-h sleep (min) | 631.500 | 69.107 | 615.000 | 45.964 | ns |
| Block design (SS) | 11.428 | 2.881 | 11.433 | 3.116 | ns |
| Vocab (SS) | 13.024 | 3.181 | 13.400 | 2.585 | ns |
| Subcortical gray matter volume (mm3) | 180,425.851 | 18,442.7305 | 187,647.162 | 12,121.734 | ns |
| Total gray matter volume (mm3) | 763,904.757 | 62,615.0560 | 775,710.237 | 51,612.3048 | ns |
| Intracranial volume (mm3) | 1,306,752.024 | 112,369.782 | 1,340,497.668 | 115,688.771 | ns |
| Amygdala (mm3) | 2,948.185 | 370.813 | 3,022.676 | 297.540 | ns |
Group differences in memory, sleep, estimates of IQ, and brain were examined using ANCOVAs, controlling for both age and sex.
ns not significant, SS scaled scores.