The Longitudinal Israeli Study of Twins



The Longitudinal Israeli Study of Twins (LIST) is the largest twin study in Israel. It is a longitudinal study that is being conducted mainly in the Social Development Laboratory headed by Professor Ariel Knafo at the Psychology Department of the Hebrew University in Mount Scopus, Jerusalem. The participants in the study are pairs of twins and their families from all over the country. The study deals with the development of children's social behavior and focuses mainly on the development of pro-social behavior: the tendency to help, cooperate, share and be empathetic. As of 2012, around 1600 families have participated in the study.

Being a longitudinal research, this study has followed the twins over a course of a few years in order to examine changes in their development. In the beginning, data was collected on twins from all over Israel that were born in 2004-2005. When the twins turned three, questionnaires regarding the twins' temperament and behavior were sent to their parents. Throughout the study, the families were invited to participate in meetings held at the lab or at their homes in four different time periods: when the twins turned 3.5, 5, 6, and 7. During these sessions, the twins took part in an experiment that was designed to examine their social behavior in a way that would be enjoyable and experiential for them.

The study has two main fields of research:

- Researching the twins themselves: We examine their development, the relations between them and the relations between them and their parents. The study aims to answer questions such as: Are there differences in the development of twins compared to the development of non-twins? Is there dissimilarity between the different kinds of twins in certain abilities or in the quality of the bond between them?

- Researching the development of certain traits and behaviors: The shared genetic heritage of identical and fraternal twins enables us to examine one of the most important questions in Psychology; nature or nurture? In other words, what is the extent of influence of genetic or environmental factors on human development? LIST focuses on researching the development of pro-social behavior and aims to answer questions such as: What is the role of age in pro-social behavior? What is the connection between cognitive abilities and pro-social behavior? What are the critical factors in the development of pro-social tendencies- genetic or environmental factors? How do environmental factors such as parenting and life events work together with children’s genetic tendencies to affect their social development?