At the beginning of “The Twinning Reaction,” it’s hard to see the true impact of separating twins to different adoptive families. But the sense of loss the separated twins feel — without understanding why — becomes more and more evident as the movie continues.

“The Twinning Reaction” explores the results of an experiment conducted by Peter Neubauer, a child psychiatrist, and Viola Bernard, a child psychologist, beginning in the 1960s.

Jewish twins adopted through the Louise Wise Services adoption agency in New York were separated to study the impact of nature vs. nurture. The adoptive parents were never told that they adopted a twin or what was being studied.

Therefore, the children themselves never knew they were twins. Only by haphazard circumstances did any of them ever find out.

The study has been in and out of the news for years as different twins have discovered the truth. This documentary, named for the unique bond between twins that begins in infancy, follows some of the people who have learned that they were subjects in the twin study.

In a process that seems unthinkable now, these children were studied regularly for years without any knowledge of the reason behind the research.

As the twins and their adoptive parents struggle to grasp the true loss and to understand the purpose of the study, it becomes clear that the lasting impact is deeper and more hurtful than originally thought.

Writer and director Lori Shinseki aims to show the negative effects of the study, and, when seen through the eyes of the subjects, it’s difficult to view the experiment any other way.

The audience sees all the twins and their parents — adoptive and birth — struggle with the time the siblings will never get back and follows the story of one set of twins seeking through legal action to get access to the study’s results of the study, which were never published and have been sealed by universities.

“The Twinning Reaction” tells a unique story of loss, sacrifice in the name of science and questions that will haunt those affected for years to come.

(Atlanta Jewish Film Festival screening: Feb. 3, 6:35 p.m., Springs; Feb. 4, 1:30 p.m., Springs)