Evolutionary perspective on decreases in grief intensity for deceased twin and non-twin relatives: An update

Abstract

In a study of 175 participants, Segal and Ream (1998) found that monozygotic (MZ) twins reported less decline in grief intensity following the loss of a co-twin, and that twins reported more intense and lasting grief for deceased co-twins than for other relationships. The hypothesis that female twins would report less decline in grief intensity than male twins was not supported. We re-evaluated and expanded upon these results by analyzing a larger sample of twin survivors (n = 423), informed by concepts from evolutionary psychological theory. MZ twins reported significantly higher grief at both retrospective and current time points, but the difference in the slope of decrease in grief between these groups was not statistically significant. We found a similar result when comparing participant sex, with female respondents reporting significantly higher grief at retrospective and current time points; however, sex differences in grief decline over time were not statistically significant. The present findings support the previous authors' third hypothesis that twins grieve longer and more intensely for the death of a cotwin than for other relationships, evidence of the strong social bond that is variously unique to MZ and DZ twin pairs.