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Scientists Find Rats Aren't Smarter Than Mice, and That's Important
HughPickens.com writes: There has long been a clear hierarchy of intelligence in the psychology lab, with monkeys are at the top, then rats, and finally mice at the bottom, "cute and fluffy but not all that bright." For at least a hundred years, researchers have used rats in their psychology experiments, assuming that they were the smarter of the two lab rodents. Now, Rose Eveleth reports at The Atlantic that new research shows this might not be true, suggesting mice can perform decision-making tasks in the lab just as well as rats can. "Anything we could train a rat to do we could train a mouse to do as well," says Tony Zador. This finding is important because using mice in experiments instead of rats could open up all kinds of new research options. For one thing, scientists have been able to manipulate a mouse's genome in really useful ways, silencing certain genes to figure out what role they play. There are mouse models for everything from Alzheimer's to Parkinson's. Being able to put those mice through the paces of a psychology experiment could help researchers connect diseases with the behaviors they impact.
So where did this idea that rats are smarter than mice come from, anyway? Zador says it's a historical bias. "There was 100 years of practice in training rats. And basically when people tried to treat the mice in exactly the way they treated the rats, the rats seemed smarter," says Zador. In other words, "over the course of 100 years people had figured out how to train rats, and that mice aren't rats." You might think that mice and rats would be basically the same when it comes to these kinds of things, but Zador points out that mice and rats diverged somewhere between 12 and 24 million years ago. For comparison, humans and chimpanzees split somewhere between 5 and 7 million years ago. So it's no surprise that mice behave differently than rats, and that the difference impacts their training in the lab. "The mouse is uniquely placed at the interface between experimental access and behavioral complexity, making it an ideal model for the study of adaptive decision-making. Successful behavioral paradigms, however, rely on targeting designs to the idiosyncrasies of the mouse from the outset, rather than simply assuming that mice are little rats."
So where did this idea that rats are smarter than mice come from, anyway? Zador says it's a historical bias. "There was 100 years of practice in training rats. And basically when people tried to treat the mice in exactly the way they treated the rats, the rats seemed smarter," says Zador. In other words, "over the course of 100 years people had figured out how to train rats, and that mice aren't rats." You might think that mice and rats would be basically the same when it comes to these kinds of things, but Zador points out that mice and rats diverged somewhere between 12 and 24 million years ago. For comparison, humans and chimpanzees split somewhere between 5 and 7 million years ago. So it's no surprise that mice behave differently than rats, and that the difference impacts their training in the lab. "The mouse is uniquely placed at the interface between experimental access and behavioral complexity, making it an ideal model for the study of adaptive decision-making. Successful behavioral paradigms, however, rely on targeting designs to the idiosyncrasies of the mouse from the outset, rather than simply assuming that mice are little rats."
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The rat has an estimated 200E6 Neurons and 4.48E11 synapses, and the mouse has 71E6 neurons and ~1E11 synapses.
There is at least some correlation between intelligence and the number of neurons. A cursory search found this: -- Fact or Fiction: When It Comes to Intelligence, Does Brain Size Matte? http://www.scientificamerican....
It would be interesting to find more definitive articles that support or contrast this.
Yeah, I've never understood why that should be. It's not like a larger body has more degrees of freedom to coordinate, and I'm pretty sure the motor control nerves also serve as signal amplifiers, so you don't need more brain cells to drive a larger muscle. The only thing I can think of that might scale with size is the number of sensory nerves in the skin - which would suggest that the portion of the brain associated with processing the input should scale with the square of linear size (or alternately with the 2/3 power of mass).
--- Most topics have many sides worth arguing, allow me to take one opposite you.
What did one lab rat say to the other?
I've got my scientist so well trained that every time I push the buzzer, he brings me a snack
There is actually some truth to this. I have had both rats and mice as pets. They may be equally smart, but they interact with humans very differently. A rat that is handled regularly can become very tame. My rat would curl in my lap to sleep. If hand raised rat escapes from its cage, it will seek out humans, and beg for both food and companionship. I have never seen that behavior in mice. They don't like to be picked up or handled, and they don't bond with humans.
It is similar to the difference between dogs and cats. They are about average in intelligence, but dogs are far easier to train, because they care about pleasing humans, and cats don't.
I used to work a small zoo. We fed the python snakes either rats or mice. Mostly live animals, since it was hard to get the snakes to eat otherwise. The mice didn't seem to even notice the snakes. They often climbed all over the curled snakes. I remember at one time a mouse climbed up on top and sat on the head of the python and cleaned itself. (before it got eaten)
The rats on the other hand immediately detected the snake as a threat. They hid behind things, keeping themselves obscured from direct line of sight of the snakes.
I have also had both rats and mice as pets. The rat I could teach to come to me when I whistled, the mice not so much... though maybe that was because I never tried to really train the mice. But I'm not convinced.