Cows aren't generally the first animal that comes to mind when we think of intelligence. We think of them standing in fields languidly chewing their cuds or bumping shoulder to shoulder with their herd mates as they wait for feeding or milking time. We describe people being "herded like cattle" as they shuffle mindlessly and powerlessly through airport security lines. There's the insult of calling someone a "stupid cow."
But vegetarians and animal rights activists have long argued that cows have more emotions and intelligence than we give them credit for. As it turns out, they are probably right. At least one organization says that cows have been observed to develop friendships with other cows, hold grudges and mourn the loss of their calves to death or separation.
Researchers at the University of Cambridge found that not only were cows capable of learning how to open a gate to get a food reward; they also reacted to their learning accomplishments by displaying increased heart rates and vigorous movement, which one animal researcher called evidence of a "eureka" moment similar to what humans experience when they learn something new [sources: Balcombe, Hagen and Broom].