Table 4.
Final Model: Indirect Effect for All Infants, Direct Effect Conditional on Risk Group
| 15-month RJA (mediator) | ||||
|---|---|---|---|---|
| Model | Coeff (B) | SE | p | |
| 12-month imitation | a | 0.51 | 0.26 | 0.05 |
| Constant | - | 0.50 | 0.40 | 0.22 |
| 12-month RJA | cov | 0.45 | 0.11 | 0.00 |
| 12-month EV | cov | 0.04 | 0.04 | 0.29 |
| 15-month EV | cov | −0.01 | 0.01 | 0.47 |
|
R2= .20 F (4, 79) = 5.07, p <.001 | ||||
| 18-month expressive vocabulary (outcome) | ||||
| Model | Coeff (B) | SE | p | |
| 12-month imitation | c’ (HR) | −4.56 | 5.25 | 0.39 |
| 15-month RJA | b | 3.20 | 1.75 | 0.07 |
| Constant | - | 5.07 | 7.50 | 0.50 |
| 12-month RJA | cov | −0.18 | 1.92 | 0.93 |
| 12-month EV | cov | −1.60 | 0.60 | 0.01 |
| 15-month EV | cov | 2.55 | 0.23 | 0.00 |
| Risk group | 28.97 | 10.57 | 0.01 | |
| Risk group*imitation | 17.22 | 7.94 | 0.03 | |
|
R2= .72 F (7, 76) = 27.77, p <.001 | ||||
| Mediation inferences | |||||||
|---|---|---|---|---|---|---|---|
| Group | Coeff (B) | SE | t | p | LLCI | ULCI | |
| Indirect effect | - | 1.64 | 1.09 | - | - | 0.24 | 5.31 |
| Conditional direct effect | HR | −4.56 | 5.26 | −0.87 | 0.39 | −15.00 | 5.89 |
| LR | 12.67 | 6.14 | 2.06 | 0.04 | 0.45 | 24.89 | |
Note: Imitation = motor imitation; EV = expressive vocabulary; RJA=responding to joint attention. LLCI = lower limit of 95% confidence interval; ULCI = upper limit of 95% confidence interval; cov = covariate. Risk group coded as 0 = HR, 1 = LR.