"Basically, it's like, 'Mum and Dad will take care of you, I don't have to see whether you do anything naughty,'" the study's author says.
In the first such alert issued by the State Department in 2014, the government urged Americans to maintain "a very high level of vigilance."
Israel, the U.S., Canada, Australia, Micronesia and Marshall Islands voted "no" for the U.N. resolution, which is not legally binding.
The woman, who was found with knife wounds, appears to be the only suspect.
Asian shares enjoyed their best day in 15 months on Friday after Wall Street boasted its biggest two-day advance since late 2011.
The children were killed and a woman, believed to be their mother, sustained stab wounds, but has reportedly survived, and is helping police.
The Australian leader has ordered a transparent government review into the events that led to the siege.
Australian Prime Minister Tony Abbott said a transparent probe would be carried out to determine the cause for failing to monitor the assailant.
Business sentiment among Asia's top companies rebounded in the fourth quarter to the second-highest level in almost three years.
Australian Prime Minister Tony Abbott and his wife, Margaret, joined several others to pay their tribute to the victims of the Sydney siege.
The buying consortium includes China Travel Financial Holdings, York Capital Management Global Advisors and Pepper Australia Pty Ltd.
Two hostages and the gunman, a self-styled Islamic cleric, died following a shootout after midnight.
"Lone-wolf" attackers are not required to pledge allegiance to a terrorist group, nor do they have to coordinate their moves.
Several Jewish institutions have beefed up security measures after a gunman took dozens of people hostage at a café in Sydney.
A barrage of gunfire and explosions came as heavily armed police stormed a café where an Iranian man held more than a dozen people hostage.
At least one of Australia's radical Muslim organizations uses the flag displayed in the Sydney siege, but it isn't ISIS.
The hashtag went viral within hours, and Twitter users from around the country have offered to ride public transport with Muslims.
Shark attacks in Australia have claimed at least six lives over the last two years.
Law enforcement officials in the Australian city prepared for a night of negotiations with the suspect, who remains unidentified.
The demands raise concerns that ISIS' call to Muslims to launch attacks in their own nations has been heeded for the first time.
Craig Stoker was reportedly coming out of the Lindt Chocolat Cafe when he bumped into one of the men who later held the cafe hostage.
The Australian National Imams Council and the Grand Mufti of Australia both condemned the act in a joint statement.