NEW ORLEANS--Sheep may all look alike to you, but not to another sheep. A few years ago, researchers led by Keith Kendrick of the Babraham Institute in Cambridge, U.K., reported that sheep, like humans, have specialized neurons that focus on faces, and that they can remember faces for years.
Now Kendrick and colleagues suggest that sheep's mighty powers of recollection might rest in part on the ability to form mental images in the absence of visual input.
The team showed sheep a video, filmed from a sheep's-eye view, while recording signals from face-sensitive neurons. In some videos, the camera swept through a corridor and turned into a stall to reveal a sheep. In others, the same camera path ended at an empty stall. The face-sensitive neurons revved up similarly in both cases as the camera rounded the curve, suggesting that the sheep were generating a mental image in anticipation of seeing a face. Sheep can recognize a particular profile even if they've only seen the sheep before from the front, indicating that they remember the earlier image and mentally rotate it. The research was described here last week by grad student Mei See Man at the Society for Neuroscience meeting.
In their ability to recognize faces from new angles, sheep outperform humans, points out Nancy Kanwisher of the Massachusetts Institute of Technology. This fits with the team's finding that, compared to primates, sheep have a larger percentage of neurons that respond to faces regardless of viewing angle.
Kendrick's lab site