Just like howls, growls, and grunts, barks are an alarm signal, especially if you don't see where they are coming from. They indicate a feeling of insecurity and fear of the possible influence of negative external factors.
Gallery of dreams
Some people can recognize dreams while sleeping; this type of dream is called lucid dreaming. Most of the people would have experienced this type of dream atleast once in their life. You can actually control these dreams. One of the popular dreams that most of us experience is as flying in the sky; you can try lucid dream by imagining your house beside the flying aid.
Types of sleep
There are two types of sleep that most of the humans undergo - REM and NREM. REM refers to the Rapid Eye Movement and NREM refers to Non-Rapid Eye Movement. Every individual will alternate these two types of sleep. Non-REM sleep will occur for a short period of time in the first stage of your sleep followed by the REM sleep. Dreams occur during the REM stage, where it lasts for 20 minutes. According to a researcher, J. Allan Hobson, dreams that occur in REM stage are usually forgotten when the individual wakes up. Studies conducted on patients during sleep shows that the frontal lobes in the brain, that are responsible for storing information, are inactive during the REM stage, which is the main cause for forgetting the dreams. Studies also show that this is the stage where you have the most intense dreams.