Rat Language-Linked Skills and Hear Rats Laugh

July 09, 2009

"Language" is a word that seems to cause more flinching in scientists than that other famous "L" word. Here's a little known fact: No one can really define what language exactly is. Sure, you can look it up in Webster's, but at a deeper level, a true definition for language has yet to be agreed upon by researchers.

Studies relating to language seem to mirror cancer research, since we're still in a phase of trying to figure out what's behind the phenomenon before going much further. At present, there's a fair amount of analysis on how skills associated with human language can be found in other animals. Please check out our story this week on how monkeys can tell the difference between a prefix and a suffix.

And read on to learn how rats now fit into the language picture.

Robin Murphy of the University of London and colleagues determined that rats can learn rules about sequences. That's the secret behind cotton-top tamarin monkeys understanding the difference between prefixes and suffixes. We humans don't give the skill much thought, but it helps to govern how we put together words and sentences.

Murphy and team found that rats could distinguish a pattern like XYX from the patterns XXY, XYY and so on. How they proved this was by reinforcing one pattern- like XYX- with a food reward. The rats saw flashing lights that matched the patterns. The scientists next replaced the lights with audible tones. The rodents still made the right distinctions.

(Rat photo: US National Park Service)

So what does this have to do with language? When we put together a sentence such as, "The dog barked at the woman," order of the words helps to convey meaning. The woman didn't bark at the dog (at least I hope not) but the dog barked at the woman. Rats and monkeys get the concept of audible order too, so we can scratch that skill off the list of what's so unique about human language.

(Shakespeare: Wikimedia image of National Portrait Gallery holding)

While no one has yet deciphered rat vocalizations, I doubt that there's a rodent Shakespeare in their midst. Whales, dolphins and even ground squirrels seem to have more complex sound production skills. As for us, it could be that human language simply relies upon multiple skills, all found in other species, but none in the unique combination or quantity that we possess.

Time will tell, however, if we are the only animals on earth that can truly lay claim to "language." Rats could still get the last laugh.