evolutionary psychology

Friend or foe? A California two-spot octopus (Octopus bimaculoides) gives observers the eye at the Marine Biological Laboratory in Woods Hole, Mass. Tom Kleindinst/Marine Biological Laboratory hide caption

A 17-year-old male bonobo eats while his son watches in the Lola Ya Bonobo Sanctuary, Democratic Republic of Congo. Fiona Rogers/Getty Images hide caption

Muslim women praying together in the Istiqlal mosque in Jakarta, Indonesia. Afriadi Hikmal/Getty Images hide caption

A young man records a voice note. A new dating app called Waving lets you swipe right on someone based only off short voice profiles. Getty Images hide caption

Rats and people may rely on "metamemory" in a variety of different ways, scientists say. For a rat, it's likely about knowing whether you remember that predator in the distance; for people, knowing what we don't know helps us navigate social interactions. fotografixx/Getty Images/iStockphoto hide caption

Lily chases sheep for the first time in her shepherd-mix life, at Raspberry Ridge Sheep Farm in eastern Pennsylvania. Several times a year the farm invites dogs for "herding instinct tests." Fred Mogul/WNYC hide caption

Male and female tungara frogs. Among these frogs, the guy with the best call usually wins the gal — except when you throw a third-choice loser into the mix. Alexander T. Baugh/Encyclopedia of Life hide caption