When pups are between 2 and 3months old, their mothers will abandon them for any number of reasons. With no mother to watch out for them, infant (婴儿) mortality of pups under one year skyrockets (飞涨) to around 90%. So, only about 10% of motherless, homeless pups survive.
Without mothers, how are these abandoned pups supposed to survive? For the study, researchers Clive Wynne at Arizona State, Nadine Chersini at Utecht University, and Nathan Hal at Texas Tech University brought in 51 college students and asked them to rate the attractiveness of headshots (头部特写) of puppies at different ages.
The pups peaked at different ages, but they were all ranked likable between six to eight weeks, since newly abandoned pups are competing with each other for human heartstrings (怜悯), evolution says they should be most likable around 6 and 11 weeks. This is around the time they are weaned (断奶) and let go of by their mothers.
There are a few characteristics that humans find particularly adorable across species: big, forward-facing eyes, floppy and unstable limbs (肢), and a soft, rounded body shape. We're also keen to scream when animals have large heads in comparison to their bodies, and this reaction goes back to evolution.
Called kinderschema (婴儿萌), these qualities are also apparent in human babies and necessary for their survival. The characteristics activate the decision-making part of the brain to encourage you to protect and nurture the baby. At the same time, the brain's pleasure center releases dopamine (多巴胺). With these two reactions, your brain makes you want to protect the baby and rewards you for doing so. With your protection, the baby can survive.
