Table 3.
Performance of siblings and controls on the measure of general cognitive ability “g” and across individual cognitive domains.
| Siblings |
Controls |
dferror | F | p | |||||
|---|---|---|---|---|---|---|---|---|---|
| n | mean | (SD) | n | mean | (SD) | ||||
| General Cognitive Ability “g” | 357 | −0.232 | (0.53) | 649 | −0.024 | (0.50) | 1001 | 16.52 | <.001 |
| Processing Speed | 363 | −0.346 | (0.74) | 679 | −0.052 | (0.78) | 1037 | 30.28 | <.001 |
| N-back Performance | 256 | −0.508 | (1.00) | 612 | −0.027 | (0.85) | 863 | 24.56 | <.001 |
| Span Working Memory | 359 | −0.150 | (0.88) | 545 | −0.025 | (0.84) | 899 | 0.56 | .455 |
| Verbal Memory | 363 | −0.153 | (0.84) | 679 | −0.019 | (0.85) | 1037 | 1.77 | .184 |
| Visual Memory | 360 | −0.036 | (1.00) | 407 | −0.041 | (0.94) | 762 | 1.67 | .196 |
| Card Sorting Ability | 358 | −0.274 | (0.90) | 655 | −0.030 | (0.84) | 1008 | 7.01 | .008 |
Analysis of covariance (ANCOVA). ANCOVA controlling for age, education, and race differences examined how siblings and controls differed in “g”. Included in general cognitive ability “g” are the six cognitive domains listed above; “g” is a mean value of the performance in the six individual domains. Following significant effect of schizophrenia risk in a multivariate analysis of covariance (MANCOVA) of the six domains, ANCOVAs were completed for each domain. All statistic values are F from ANCOVA, adjusting for age, education, and race. Bold indicates p < .05.