【英语时差8,16】母婴联系（在线收听）

 However, the observation that morphine can decrease social behaviors as well prompted scientists to investigate the connection between the opioid system and social relationships. They compared normal baby mice to baby mice lacking a crucial opioid receptor. What they found was that while normal baby mice who have been separated from their mothers make distressed noises, baby mice that lack the crucial opioid receptor exhibit significantly less distress when mom’s away.