There is an English proverb that says, Let Sleeping Dogs Lie. It means to not bring up an old problem. Researchers in Hungary have found another reason to let dogs keep on sleeping. It seems the animals are learning while they sleep. The scientists placed wires on the dogs' heads to measure electrical activity in the brain. The brain activity, called sleep spindles, takes place in human beings, and has been linked with learning. The Hungarian scientists hope to understand how the dogs' ability to learn and remember changes as they get older. The study may help researchers understand how human brains change as we age.