The Twin Inventory of Relationships and Experiences (TIRE): psychometric properties of a measure of the non‐shared and shared environmental experiences of twins and singletons

We examined longitudinally the psychometric properties of the Twin Inventory of Relationships and Experiences (TIRE), an instrument designed to assess non‐shared and shared environmental experiences in twins and siblings. A community sample of 1,117 pairs of like‐sex monozygotic and dizygotic twins, aged eight to 16, and their parents, was used. Results indicated that the TIRE provided constructs that are consistent across informants, gender and time. These dimensions showed good longitudinal stability within raters, and low to moderate inter‐rater agreement; the results are consistent with those of other studies using different instruments to assess family environment. It is concluded that the TIRE may be used to assess dimensions of the non‐shared environment of twins and siblings and their influence on children's development.