Want to know if your dog loves you? Watch his left eyebrow. Researchers have used high-speed video cameras to capture the subtle facial expressions of 12 dogs of various breeds. Each animal was led into a room divided by a curtained partition. Then the curtains briefly parted, and the dog might see its owner (who was instructed to show no emotions), an unfamiliar person, or an object the dog loved, such as a squeaky ball, or an object it feared, such as nail clippers, for 800 milliseconds. The scientists marked the dogs’ faces with blue tape to pinpoint their facial tics. The dogs’ facial expressions varied in response to what they saw, the scientists will report in an upcoming issue of Behavioural Processes. When the dogs saw a person, they lifted their eyebrows—and if the person was their owner, they raised their left eyebrow even higher. (In the video, the poodle’s eyes widen slightly as its eyebrows rise and ears drop when its straight-faced owner appears.) Strangers caused the dogs to move their left ears back slightly, a sign of caution. Beloved toys elicited no response, but those dreaded nail clippers caused dogs to twitch their right ears—perhaps a sign of a learned response, which is governed by the left side of the brain. Some of the results are puzzling, the researchers say, because previous research showed that dogs’ positive emotions are displayed on the right side of their faces. Why then did the pooches raise their left eyebrows upon seeing their owners? It may be due to mixed emotions—something dogs were not known to experience. While seeing their owners made the animals happy, they were blocked by the partition from reaching out for that all important touch—which made them sad.