Working toward sustainability means working together. It may require sacrificing now to make possible a better future. It calls on all of us to keep in mind the common good.

So how is it that when we face a crisis like the coronavirus pandemic, people cram their grocery carts full of toilet paper while simultaneously glaring at—and shaming on social media—others who are doing the same thing?

"As a behavioral neuroscientist who has studied hoarding behavior for 25 years, I can tell you that this all normal and expected," said Stephanie Preston, professor of psychology at the University of Michigan. "People are acting the way evolution has wired them."

Preston wrote about hoarding and shaming at The Conversation, an online platform for academic experts to share their perspectives about topics of current interest.

"Hoarding is actually a totally normal and adaptive behavior that kicks in any time there is an uneven supply of resources," Preston said.

Everybody hoards; that's what you're doing when you stock your pantry during your weekly grocery run. In times of stress, our brains tell us to kick that behavior into high gear. The same happens with other animals, Preston said:

"For example, a kangaroo rat will act very lazy if fed regularly. But if its weight starts to drop, its brain signals to release stress hormones that incite the fastidious hiding of seeds all over the cage."

As for the shaming, Preston said that's related to what economists call "the tragedy of the commons," first discussed in relation to the common grazing land once shared by inhabitants of rural villages.

The "tragedy" occurs when individuals pursuing their own self-interest (letting their cows graze all they want) conflicts with the common good (preventing damage to the resource from overgrazing).

Shaming can prevent such a tragedy. "Who wouldn't pause before grabbing those last few rolls of TP when the mob is watching?" Preston said.

Overall, she said, "People will continue to hoard to the extent that they are worried. They will also continue to shame others who take more than what they consider a fair share. Both are normal and adaptive behaviors that evolved to balance one another out, in the long run."

In the meantime, she said, it's important to keep in mind that most people don't let selfishness run rampant:

"Most are just trying to protect themselves and their families, the best way they know how, while also offering aid wherever they can. That's how the human species evolved, to get through challenges like this together."