So much for naming your mercenary company after an obscure element from the periodic table.

Say goodbye to Xe. The company formerly known as Blackwater — the world’s most infamous private security corporation — has jettisoned the name it chose in its 2009 rebrand. Now the “security solutions provider” wants to wash away the taint of the 2007 Nisour Square shootings by adopting the new name “Academi.”

But the company is changing its name — not its core business. And it even wants back into the country where it ran its brand through the mud: Iraq.

“Our focus is on training and security services. W...

The world is a complicated place. Reality is dense with patterns, but these patterns are often subtle and inconsistent. We think we understand how things work — X always causes Y — but then Z happens. It’s very confusing.

Needless to say, such complexity poses a big problem for biology. How should animals learn from such unpredictable situations? What’s the best way to cope with contingency? We don’t need perfection, but we do require an efficient mental mechanism that allows us to maximize utility most of the time.

Enter reinforcement learning, a theoretical framework that helps explain how...