Those who defend animal research often like to point out that about ninety percent of the animals used are rodents, namely mice and rats. The upshot is that we should all breathe a sigh of relief. "Oh, they’re just rodents. Why should we be concerned?"

Why indeed? Well, for starters, rodents have sentience and emotions—they think and feel. They build nests and feed their young milk. Versatile and resourceful, mice and rats thrive on our success despite our concerted efforts to annihilate them. Their primary senses are smell and sound. They can recognize individuals by smell, and mice, at least, can even smell how closely another mouse is related to themselves. Recent studies reveal that mice show empathy (see my blog 16 Sept 06) and that males sing courtship songs to females. When tickled, tame Norway rats make ultrasonic chirps linked to the origins of human laughter, and like kids to an ice-cream van, they will run for more.

Now, experiments from the University of Georgia indicate that rats know what they know. Rats were rewarded for pressing the correct lever assigned to either a long (2 to 3.6 seconds) or a short (4.4 to 8 seconds) noise played back to them. Before they could press a lever, however, they were required to poke their noses into one of two holes, one of which voided the current trial and advanced to the next one, and the other of which communicated that the rat was going to press one of the levers. Food pellets were dispensed depending on what choice the rat made: a small reward of pellets for choosing to advance to a new trial, a large reward of pellets for a correct lever choice, and no pellets for an incorrect lever choice.

If the noise was obviously long (e.g., 6 seconds or more), the rats almost always voted to take the test, which usually resulted in their getting the large reward for a correct answer. But if the discrimination was difficult (e.g., a 4.4 second noise), the rats usually voted to void the trial, earning a modest reward in the process. Thus, rats are capable of judging whether they have enough information to pass a test. The fancy term for this sort of mental capability is metacognition.

One of the articles that reported this study (http://www.world-science.net/othernews/070308_rats.htm) asked: "Does it mean that rats are ‘conscious’?" I posit that if they aren’t, then neither are we.