With a few liberating swipes of their paws, a group of research rats freed trapped labmates and raised anew the possibility that empathy isn’t unique to humans and a few extra-smart animals, but is widespread in the animal world.

Though more studies are needed on the rats’ motivations, it’s at least plausible they demonstrated “empathically motivated pro-social behavior.” People would generally call that helpfulness, or even kindness.

“Rats help other rats in distress. That means it’s a biological inheritance,” said neurobiologist Peggy Mason of the University of Chicago. “That’s the biological ...

SAN FRANCISCO — Twitter launched a site-wide redesign on Thursday, completely reworking the user interface in an effort to be better understood to a wider audience.

‘We can and have an obligation to reach every person on the planet.’

The redesign, which is currently being rolled out to users over the next few weeks on mobile devices and the web, consolidates a number of Twitter’s existing features into four separate categories, the better to organize a growing sense of information overload.

“We have to provide the simplest and fastest way for people around the world to connect with everything,” T...