Is babies’ anxiety toward strangers caused by genes or the environment?

Is babies’ anxiety toward strangers caused by genes or the environment?

A lot of babies exhibit anxiety toward strangers. Anyone with a baby is aware of this phenomenon. However, we are still not sure of the reason for this behavior. Is this anxiety toward strangers hereditary, or is it caused by the environment that the babies were raised in?
This anxiety toward strangers appears in most babies 6 months after they are born. However, there is a great amount of individual differences in this phenomenon; the period of onset and degree to which babies exhibit this phenomenon are diverse.
In most cases, such anxiety goes away during natural development. However, there are children who continue carrying this anxiety toward strangers. This tendency can differ among siblings. As such, the mechanism behind this phenomenon is still unknown.
On the other hand, the term “anxiety toward strangers” is used on a regular basis. Some people tell mothers of babies that exhibit severe anxiety toward strangers that, “It is evidence that the baby is able to differentiate between their mother and other people.” However, this information is inaccurate because it is known that babies can differentiate between their mothers and other people immediately after birth.
Therefore, the reason why anxiety toward strangers emerges is not because babies are able to differentiate them from their mother. Rather, babies who had been able to differentiate their mothers from others right away (and did not show any anxiety toward strangers) start to show anxiety six months after their birth.
By focusing on this mysterious behavior, we decided to clarify the mechanism of stranger anxiety. Although we have already reported about a part of the mechanism of this behavior, we are still completely uncertain about whether this behavior is caused by genes, the environment, or both.
Therefore, we launched the Babies’ Stranger Anxiety Gene Project to investigate the amount of influence genes have on this phenomenon.
The term “hereditary” refers to “the parent’s characteristics being passed onto the children.” Here, the term “disposition” also includes facial features, body types, and personalities. The so-called “disposition” is impacted by genes—and by the environments that one was born and raised in.
However, genes play a crucial role in the formation of one’s physique and personality at a fundamental level. Believing that there might be genes related to being prone to experiencing anxiety toward strangers, we decided to search for such genes.


If you want more information on the research….

  1. For more details, apply to participate in the study. During this time, we mail a briefing and consent forms to the potential participants. Those who would like to participate are asked to fill in and sign the consent form, and send it back, along with their baby’s nail clippings. Even when consent for the study is not provided, there is absolutely no penalty.
    Even after the participants have agreed to the study, they can withdraw their participation at anytime. No penalties will occur due to their withdrawal.
  2. Thereafter, we ask the participants to check the stranger-anxiety level of their babies once a month—until they turn 1.5 years (i.e., 18 months) old. The participants can submit such data online. Access to the site with the questionnaire will be provided to our participants after they’ve applied to take part in the study. Because we ask our participants to answer using an ID number (not their names), there is no concern that personal information will be leaked to third parties.
  3. For the protection of personal information, we perform the analysis of genes and questionnaire results by adopting a method that conceals the participants’ names and addresses—so that individuals cannot be identified. Such data may be published in academic journals after it has been statistically processed. The personal information of the babies and their parents will never be released.
  4. The personal information that our participants have provided will be separately stored as research data in a secured area. We will ensure the disposal of the data when the research is completed, by using a shredder and chemicals.
  5. Please contact our staff members at any time for questions on research.
  6. We offer a small compensation to all participants.
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