Happy Is As Happy Does
Table 2. Nine-year retest correlations of the MPQ Well Being scale.
|
NUMBER OF PAIRS |
I INTRACLASS R | |
|
Cross-Time or- |
410 |
.55(±.02) |
|
Cross-Time Cross-Twin |
131 |
.54 (± .03) |
|
DZ Twins: |
74 |
.05 (± .07) |
If happiness varies over time about a set-point that is characteristic of the individual then, of
course, it should be the level of that set-point that reflects genetic influences. The MPQ-Well-
Being scale has a high alpha reliability and the 30-day retest reliability also is quite high. But
when we retested 4 10 of our twins some 9 years their first testing, the retest correlation for well-
being was only .55. On the other hand, the scores of MZ twins on the first testing correlated .54
with their cotsvor ’ s scores 9 years later. That is, the cross-twin cross-time correlation is
essentially equal to the retest or within-twin cross-time correlation, and this would suggest that
the heritability of the set-point of nearly 100%. Meanwhile, the cross-twin cross-time correlation
for the 74 pairs of retested DZ twins was only .05 which, when corrected for attenuation in the
same way, rises only to .09.