In the world of squirrel researchers, Stephanie Preston, a professor of psychology at the University of Michigan, is a bit of a legend. “She’s the one that actually discovered the head flick and it was first to document it,” says Mikel Delgado, a postdoctoral fellow at the School of Veterinary Medicine at the University of California-Davis.

That head flick is just one of several ways that squirrels assess nuts to either eat them or store them away for the winter. “She showed that the squirrels were actually weighing the nut as they shake their heads,” says Lucia Jacobs, professor of psychology at the University of California-Berkeley, where both Delgado and Preston did their graduate work. “She came to me as a graduate student and said, ‘Look what I found.'”

Squirrels are central to the work at Jacobs’ interdisciplinary lab, which is featured in the wonderful new Nature documentary, A Squirrel’s Guide to Success on PBS. What she and her colleagues have found is that squirrels are incredibly systematic and methodical when it comes to nut storage, particularly squirrels that store food for the winter by scatter hoarding—burying many nuts over a wide area. The scientists suspect that the behavior requires so much brain power that it accounts for brain growth they’ve observed in some types of squirrels during prime nut-hoarding season.

Read the full article at Quartz.