Dreams are defined as mental activity associated with the rapid-eye-movement period of sleep. They are normally made up of a lot of visual images, scenes or thoughts expressed in terms of seeing rather than in those of the other senses or in words. Electroencephalograph readings, which measure the electrical activity of the brain, show that young adults dream for 1 1/2 to 2 hours for every 8-hour period of sleep. Babies spend about 50% of their sleep in the REM phase - much more than adults - a figure which diminishes steadily with age. …
