These questions and answers concern "sensorimotor dreams" the most common type, which are also the foundation of social dreams.
What Causes Dreams?
During REM sleep, an area in the brainstem called the pons becomes active, causing the eyes to move about. Some researchers (e.g., Alan Hobson) believe that the pons activity is random and has no intrinsic meaning or purpose.
The pons is connected to the sensorimotor cortex at the top-center of the brain, and activates neural circuits there for basic sensorimotor behavior, such as reaching, walking, and moving the eyes.
The sensorimotor activation is not strong enough to cause actual bodily movement (other than in the eyes), or actual sensations, but it is strong enough to be experienced by the dreamer as reaching, walking, looking, and so on, and that is the dream: experience of random activity in the sensorimotor cortex.
Why do dreams seem meaningful?
Dreams seem meaningful because when you remember them you are awake, at least awake enough to say, "Wow, what a dream! I dreamed I was ..." When we are awake, we seek meaning and we find it. That's why there is a face on the moon -- we do not like random, meaningless patterns, and especially not random, meaningless experience.
As we recall the dream experience, we invest it with emotional and social significance. The process is like creative story telling. A list of the brain areas that were activated would be like a list of random paragraphs. But in recalling the dream events, we make them into a (more-or-less) meaningful story.
What is the meaning of this dream?
The source of the dream has no more meaning than a burp, because it originated from some brain circuits that became lightly activated as part of an automatic bodily process. But the dream report has all the personal meaning that any story you made up would have. As a creative product it reflects your interests, experiences and concerns, whether those are explicitly acknowledged by you or not.
Do most dreams have sexual or aggressive meaning?
There are basic brain circuits for sexual or aggressive acts, and these might have been activated during REM sleep, which you would have experienced as sexual or aggressive urges. In the same way, if you have an empty stomach or a full bladder, you might experience those in a dream as food scenes or as swimming in the ocean. You provide detail as you create the dream story at recall.
Do certain dream images have fixed symbolic meaning?
Certain images or thoughts have commonly recognized meaning because they are well-known cultural images. You don’t need an unconscious id or superego dreamwork for a sexual interpretation of a train plunging into a dark tunnel. It's a common image suitable to describe having experienced activation of a sexual arousal circuit. However there is no justification for most interpretations listed in books of dream symbols.
Does dreaming of spiders mean you fear being engulfed by your mother? There is no necessary connection. However, brain activation of tactile (touch) receptors on the skin could appear in a dream report in any number of expressive ways, including feeling enveloped, smothered, hugged, or covered in spiders.
Are dreams the royal road to the unconscious?
Analysis of dream reports can reveal hidden motives, attitudes and beliefs of the dreamer, but so can analysis and discussion of TAT stories (Thematic Apperception Test) and Rorschach (“inkblot”) responses, artistic products of all kinds, and even ordinary conversation. Dream reports may be fertile for this kind of exploration because they are typically recorded when the author is not fully awake, but they are not any more "royal" than any other creative product.
Why can I fly in my dreams but not in real life?
The dream story tries to accommodate the feelings of lightly activated brain circuits. If an activated sensorimotor pattern involves movement in space, then coordinated visual input would change accordingly. Sensorimotor patterns are interconnected in that way. But that particular complex of sensorimotor pathways might not involve any activation associated with walking or running, for example.
So how is the awake self, constrained by reality, supposed to interpret this vague dream experience? “I feel like I moved from Point A to Point B, and the perceptual scenery changed appropriately as I moved, but I didn’t walk or drive, or bicycle or swim. I don’t know how I did it. So I must have flown.” That is the most direct and “logical” explanation consistent with the “memory” (feeling) of the dream-activated sensorimotor circuit.
Why are dreams bizarre and irrational?
Dream reports are bizarre and irrational because they are waking fabrications constrained by the real world that attempt to articulate correlations between sensori and motor patterns felt in the brain. The dream story tries to flesh out a narrative from those minimal patterns and the result is like trying to construct a sonata from random groups of notes. The result is not likely to have much structural integrity, but might be creative and amusing.
Is it true that every dream is two dreams?
Yes. As psychoanalysts have said since Freud, every dream consists of the manifest dream report, and under that, the latent dream. The purpose of dream analysis is to use the manifest to understand the latent. But that process is no different in principle from how we analyze an utterance into its surface and deep structures or deconstruct an essay into its implicit meanings. Every human communication and social artifact has at least two levels: the manifest, realized product, and its latent, underlying intent. A dream report, as a creative product, is no exception.
Do we dream in color or black-and-white?
Neither. Dreams are attempts to explain certain bodily feelings, those of lightly activated brain circuits. Brain circuits have no color. It is completely dark inside the skull. However, the dream report might use either color or monochromatic imagery as appropriate in its construction.
Why can’t I remember my dreams?
What you have are feelings of lightly activated brain circuits at certain times of night. If you are not willing or able to conceptualize those into imaginative stories, then there are no dreams.
Is a dream a message from another dimension?
No, it is a complete fabrication of your own, formulated around dim experience of some lightly activated brain circuits.
Can I have a dream that does not belong to me?
Not unless you have circuits in your brain that don’t belong to you. However, you might construct a dream report using elements from public stories.