iTwin is an online research study of adult twins. Our site is still under construction, but please join our email list to be notified when the participant portal launches. If you have ideas for how this project can best serve the twin participant community, please email us.

About iTwin

We provide validated survey measures of personality, attitudes, and beliefs. You will receive results after finishing each survey, and can access results of surveys you have taken in the past. When your twin has also completed a survey, you will learn about how similar you two are compared to other pairs of twins.

Any adult twins can join iTwin. There are no limits on location, but our consent and study materials are currently only available in English.

When you sign up, we will ask for both your email address and your twin’s email address, and we will send your twin an invitation to participate, as well.

Why a Twin Study

Twins share a special relationship – two people, born at the same time, who share either 100% of the same DNA (in the case of identical or monozygotic twins) or 50% of the same DNA (in the case of fraternal or dizygotic twins, who are no more genetically similar than any pair of full siblings).

The unique relationships of twins are helpful for understanding how people in general can turn out so differently from one another, even when raised in the same family or culture.

  • If, on average, identical twins are more similar to one another than fraternal twins are, then genes influence behavior.
  • If identical twins and fraternal twins are equally similar, then shared experiences influence behavior.
  • If identical twins are not exactly the same as one another, then unique experiences influence behavior.

Most twin studies are limited to small geographic regions, and require that twins visit a research lab in person to participate.

iTwin allows twins from all over the world to participate in research at their own convenience. A project that is entirely online also lets us quickly and easily add new studies, so that we can ask and answer important scientific questions as they arise.

Participant Privacy & Data Security

iTwin is designed with participant privacy and data security in mind. Your data in the participant portal (where you fill out surveys) is labeled only with an anonymous code number.

During the consent process, we do require some identifying information, including your email address and date of birth. We collect and store consent forms and associated identifiers on a separate HIPAA-compliant system, hosted by the Interdisciplinary Health Sciences Institute. Our purpose here is two-fold:

  • to document that each participant has given informed consent, and
  • if at any time you would like to obtain a copy of all of your collected data, or to withdraw your consent, we would be able to identify the person making the request as the person associated with the data.

We will only report results in the aggregate (that is, descriptions of groups, never individuals). We will never share participants’ identifying information with anyone. Anonymous data may be shared with other academic researchers, under strict conditions of data security and ethical use. We will never share raw data publicly or with for-profit entities for any purpose or price.

Frequently Asked Questions

How often will I be asked to participate?

You may log in to take surveys and view your results at any time. We will sometimes contact you with news about study opportunities, results, or features, but we do not require that participants follow any set schedule.

Do you pay participants?

iTwin is not currently running any paid studies. However, we plan to add this feature in the future.

Would I need to provide a DNA sample?

No. We have no current plans to collect DNA or biological samples of any kind.

Analysis of twin data relies on knowing the zygosity of each twin pair (identical or monozygotic versus fraternal or dizygotic). We establish zygosity using the “Peas-in-a-Pod” questionnaire, which has been validated as accurate at identifying zygosity compared to genetic methods.

If you are looking for the Illinois Twin Project, a study of child development for families living in the state of Illinois with twins (or other multiples) ages 0-17 years, please visit