Dreams are successions of images, ideas, emotions, and sensations that occur involuntarily in the mind during certain stages of sleep.The content and purpose of dreams are not definitively understood, though they have been a topic of scientific speculation, as well as a subject of philosophical and religious interest, throughout recorded history. The scientific study of dreams is called oneirology.Dreams mainly occur in the rapid-eye movement (REM) stage of sleep—when brain activity is high and resembles that of being awake. REM sleep is revealed by continuous movements of the eyes during sleep. At times, dreams may occur during other stages of sleep. However, these dreams tend to be much less vivid or memorable. Dreams can last for a few seconds, or as long as twenty minutes. People are more likely to remember the dream if they are awakened during the REM phase.Dreams have been seen as a connection to the unconscious. They range from normal and ordinary to overly surreal and bizarre. Dreams can have varying natures, such as frightening, exciting, magical, melancholic, adventurous, or sexual. The events in dreams are generally outside the control of the dreamer, with the exception of lucid dreaming, where the dreamer is self-aware. Dreams can at times make a creative thought occur to the person or give a sense of inspiration.
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動畫中發夢的情形
真正的作夢只有在人類身上被直接證實發生過,不過很多人相信作夢也會發生在其他動物身上。動物已經確定會有快速眼动睡眠,然而他們的主體經驗卻難以確定。平均擁有最長快速眼动睡眠時期的動物是穿山甲。哺乳類可能是大自然中唯一,或者至少是最頻繁的作夢者,因為和他們的睡眠模式有關。也有人认为上述有关梦的解释是不科学的,梦只是人睡眠时的一种心理活动,梦中的心理活动与人清醒时的心理活动一样都是客观事物在人脑中的反映。梦中离奇的梦境是因人睡眠大脑意识不清时对各种客观事物的刺激产生的错觉引起的。如,人清醒心动过速时产生的似乎被追赶的心悸感,在梦中变成了被人追赶的离奇恐惧的恶梦,人清醒心动过慢或早博时引起的心悬空、心下沉的心悸感,在梦中变成了人悬空、人下落的离奇恐惧的恶梦。梦中经常能感觉到一些人清醒时不易感觉到的轻微的生理症状,是因人睡眠时来自外界的各种客观事物的刺激相对变小,来自体内的各种客观事物的刺激相对变强引起的。