Table 2. Results of separate linear mixed effects regression models examining effects of activity type on each of language experiences.
| Fixed effects | Random effects | Chi-square test of model fit with and without effect of interest | |||||||
|---|---|---|---|---|---|---|---|---|---|
| Model outcome | Model Parameter | B | SE | t | Variance | SD | X2 | df | p |
| Peer vocalizations | Activity type | .15 | .02 | 9.27 | — | — | 85.33 | 1 | < .00001 |
| Sex | .004 | .05 | .08 | — | — | .008 | 1 | .928 | |
| Age | .0006 | .00007 | 7.71 | — | — | 57.53 | 1 | < .00001 | |
| Subject intercept | — | — | — | .005 | .07 | 30.54 | 1 | < .00001 | |
| Child vocalizations | Activity type | .06 | .01 | 4.33 | — | — | 18.71 | 1 | < .00001 |
| Sex | -.07 | .05 | -1.29 | — | — | 1.83 | 1 | .177 | |
| Age | .0001 | .00007 | 1.92 | — | — | 3.77 | 1 | .052 | |
| Subject intercept | .007 | .09 | 128.28 | 1 | < .00001 | ||||
| Adult vocalizations | Activity type | .45 | .03 | 17.61 | — | — | 302.05 | 1 | < .00001 |
| Sex | -.10 | .06 | -1.58 | — | — | 2.71 | 1 | .10 | |
| Age | .0005 | .0001 | 4.47 | — | — | 19.04 | 1 | < .00001 | |
| Subject intercept | — | — | — | .009 | .10 | 27.55 | 1 | < .00001 | |
| Turn taking | Activity type | .21 | .01 | 21.48 | — | — | 444.83 | 1 | < .00001 |
| Sex | -.09 | .04 | -2.18 | — | — | 4.70 | 1 | .030 | |
| Age | .0001 | .00005 | 2.65 | — | — | 7.02 | 1 | .008 | |
| Subject intercept | — | — | — | .004 | .0627 | 157.66 | 1 | < .00001 | |
| Overlap | Activity type | .06 | .02 | 2.27 | — | — | 5.15 | 1 | .023 |
| Sex | -.02 | .02 | -.68 | — | — | .46 | 1 | .497 | |
| Age | -.00003 | .0008 | -.33 | — | — | .11 | 1 | .74 | |
| Subject intercept | — | — | — | 1.6e-15 | 4e-8 | 0 | 1 | 1 | |
Note. 5 models are shown. Chi-square tests contrast models with and without the fixed effect of interest (with all other fixed effects present). Results indicate the robust effect of activity type (structured versus unstructured) on peer vocalizations, child vocalizations, adult vocalization, turn-taking, and vocalization overlap. Family wise alpha = .01.