Twins’ relationships strongly associated with identity

Photo: Torbjörn Berglund

(Published 2013-01-25)
There is a general belief that twins are both externally and internally equal, but to an identical twin this can be a frustrating limitation.
– There are stereotypical notions, not least in the media, that twins are the same person. It may thus be particularly important for twins to emphasize that behind the exterior are two unique individuals.

Sirpa Pietilä Rosendahl received her doctorate last summer from the School of Health Sciences in Jönköping with a thesis on twinhood. In her thesis she examines 35 older twins’ life stories with focus on individuality and relationships. Sirpa Pietilä Rosendahl first became interested in older twins while working as a research nurse in SATSA, a quantitative study on aging based on the Swedish Twin Registry.

– Through my work with SATSA, I met hundreds of twins and decided to interview a few of them to get to know more about how they felt and looked at their lives as twins. I wanted to investigate things that are not visible in a structured questionnaire, she says.

SATSA and the Gender studies helped Sirpa Pietilä Rosendahl to select the respondents involved in her own study. The selection criteria were that the subjects of study should be men and women, identical twins, same-sex fraternal twins and different-sex fraternal twins as well as twins who had been raised together or apart. The twins should be at least 70 years old and some of them should have lost his/her twin at an old age.

A central result in Sirpa Pietilä Rosendahl’s investigation is that the twins’ experience of the twin relationship is strongly associated with their identity and self-image. Twins switch between dual identities, the first identity being that of a twin, and the other being that of a unique individual within the twin relationship. In the interaction between relationship and identity, three different relationship types were found: the nurturing, the draining, and the superficial twin relationship. In the nurturing relationship the twins are very close, but their primary identities are individual. The relationship is perceived as edifying and enriching as well as a source of joy and emotional support. In the draining relationship, the joint twin identity is very strong and the individual identities weak. The relationship is described as emotionally dense and complex. In the superficial relationship the twins are not particularly close to one another, and the relationship is thus perceived as a polite acquaintance with limited emotional involvement. The individual identities of the twins are in this case very distinct.

– The survey shows that a close relationship is not always good. If the close relationship is also draining, with very weak individual identities, the loss of one twin can produce identity confusion in the other. Who died, she or I?

In one of the studies in the dissertation, the focus was on elderly twins’ grief. Such a study had never been carried out before.

– My results show that there is not a great difference between how younger and older twins experience grief. The grief is as deep regardless of age. However, one difference is that an elderly twin also loses many shared memories when the other twin passes away.

Only a few twin researchers work with qualitative methods. Most studies are based on quantitative data similar to those found in the SATSA study.

– It is important to emphasize that I do not regard my research questions as a contrast to the quantitative research, but as a complement to it. By also using qualitative data, we can get a more complete picture of a person's life story. We can observe how relationships evolve over time since the respondents have told us about their lives from childhood to old age. This may provide an expanded knowledge regarding the social aspect and it can also raise questions that may not have been highlighted before, for example concerning which impact close relationships have on health.

A longitudinal research study on aging

SATSA is a longitudinal research study that started in 1984. The subjects of study are older same-sex twins who were raised either together or apart. The aim of SATSA is to understand the nature of aging and the factors that predict healthy aging and delayed transition to increasing vulnerability and frailty.

The study includes survey data with questionnaires that were dispatched in 1984, 1987, 1990, 1993, 2004, 2007, 2010 and 2012. An additional dispatch of the survey is planned for 2014. Also interviews, medical examinations and tests of memory, thought and functional capabilities are included in the SATSA study.

With data from SATSA, it is possible to study many different aspects of aging. Some of the areas that have been analyzed are the importance of genes and environments for aging, with focus on memory and thinking ability as well as physical health. Data from SATSA include everything from genes to lifestyle and social circumstances. Some of the factors that are identified in the study are eating habits, personality, smoking, dementia, heredity, body weight, social environment and physical activity.

The SATSA material is available at ICPSR in Michigan and can be accessed via SND.