I have a Japanese wife and two children. Among our friends are Japanese-Japanese couples, international couples and French couples. The pure Japanese families have the policy of letting their kids sleep in the same bed as the parents from birth to small childhood (at least until 5 years of age). Other couples don't do that. Children get their own bed as soon as they are back from the maternity, and their own room after a few months or one year at latest.

I have observed that Japanese babies and children, who used to sleep with their parents, are nearly always more whiny, dependent and insecure. Those babies cry as soon as the mother is away, and often even when the mother is present. Babies raised with the habit of sleeping by themselves are much stronger in their mind. They can be left to play alone and won't complain. They don't get scared so easily. They are also less likely to cry when meeting strangers.

Many Japanese adults lacl self-confidence, and are often insecure (不安 "fuan" as they say). I think this is because they grew up with the constant reassuring presence of their mother near them. They were over-protected. Spoiled children become selfish, but over-protected ones become insecure.

There are many spoiled European kids, but few really insecure ones. That's because parents will buy them lots of toys to occupy them to have peace. Children play alone or with friends but don't bother their parents all the time. Japanese kids are literaly in their mother's skirts until the age of 5 or 6.

I think that many Japanese people have a weaker strength of character and are less independent-minded because of the way they were raised, sleeping with the parents until late and being over-protected by the mother.

Japanese-European couples often wonder which system they should adopt. To me the answer is clear: give the baby his/her own bed and room as early as possible.