They symbolize simplicity and ingenuity.
Body reactions during sleep
Most of us must have experienced hallucinations or night mares. When we experience such dreams we are unable to move or react. This stage is referred to as sleep paralysis. This type of dream occurs in between wakefulness and REM. As it occurs during the REM stage, it causes complete muscle weakness preventing the individual reacting to the dreams.
Do animals dream?
Research conducted by various scientists show that animals do experience dream while sleeping. They also experience similar sleep stages like human beings - REM and Non-REM. If you have noticed a dog sleep, it might sometimes wag its tail, this indicates some response to its dream. A study was conducted in a cat by removing a part of the brain stem, which will not prevent it from reacting to the dream during REM. It was noted in some cats they were aggressively chasing mice as in reality.