Passage Two
In 2011, a dog owner named robert uploaded a video titled "Guilty!" to YouTube. He had come home finding his two dogs near an empty bag of cat treats. The first dog behaved calmly. But the second dog, Denver, sat shaking in a corner, her eyes looking down, which made Robert believe it was she who had done it. Seeing her "apparent admission of guilt," he yelled at her, "You did this!" Denver beat her tail nervously. "You know the routine. In the kennel（狗窝）!" Following the command, the dog shut herself in.
The video quickly gathered a flood of comments. Since then, "dog shaming" has become popular on the internet, as owners around the world posted beside notes shots of their trembling pets in which the dogs seemed to admit bad behavior. For instance, "I ate an extra large pizza", admits a chocolate Lab. Human enthusiasm for guilty dogs seemed growing.
But according to a researcher at Barnard College, what we consider to be a dog's guilty look is no sign of guilt at all. In a 2009 study, the researcher had owners forbid their dogs from eating an attractive treat, and then asked the owners to leave the room. While each owner was gone, the researcher either removed the treat or fed it to the dog. When the owners returned, they were told—regardless of the truth—that their dogs either had or had not eaten it. If owners thought their dogs had done something wrong, blames followed, and guilty looks quickly emerged. Yet dogs who hadn t eaten the treat were more likely to appear guilty than dogs who had—so long as their owners scolded them. Far from signaling regret, one group of researchers wrote in a 2012 paper, the guilty look of dogs is very likely a means to show obedience（顺从）to their owners.
What dose "a chocolate Lab" in Paragraph 2 refer to?