Table 1.
Means, Standard Deviations, and Intercorrelations Among the Main Variables in Studies 1 and 2
| Variable | M | SD | Correlations |
|||
|---|---|---|---|---|---|---|
| 1 | 2 | 3 | 4 | |||
| Study 1 | ||||||
| 1. Respiratory sinus arrhythmia (log Hz) | 6.62 | 1.36 | — | |||
| 2. Delay-of-gratification time (seconds) | 140 | 225 | −.27* | — | ||
| 3. Child’s age (years) | 2.14 | 0.14 | .24* | .10 | — | |
| 4. Maternal educationa | 2.84 | 1.68 | −.21* | .32* | −.08 | — |
| 5. Family income (thousands of dollars) | 20.82 | 12.27 | −.17* | .24* | −.07 | .36* |
| Study 2 | ||||||
| 1. Respiratory sinus arrhythmia (log Hz) | 5.91 | 2.18 | — | |||
| 2. Delay-of-gratification time (seconds) | 463 | 210 | .03 | — | ||
| 3. Child’s age (years) | 5.29 | 0.24 | −.12 | .14 | — | |
a
Maternal education was coded as follows: 0 = none, 1 = elementary/junior high school, 2 = high-school-equivalency test, 3 = high school diploma, 4 = vocational/tech diploma or 1 year of college, 5 = associate’s degree, 6 = diploma in nursing, 7 = bachelor’s degree, 8 = master’s degree, 9 = doctoral degree.
*
p < .05.