imagery occurs during the nodding off stage, and can vary
considerably, from startling warnings and vivid precognition,
to static scenes. Sometimes voices are heard, even entire
conversations. In sleep research generally, the hypnagogic
state is perhaps underestimated.
Researchers tend to accept that it represents the first
stage of sleep, but are more interested in other sleep
phenomena. This underpins the point that, as far as knowledge
about sleep and dreams is concerned, we are merely scratching
the surface. Within the realm of hypnagogic imagery lies
a mysterious world that, if better understood, can offer
Hypnagogic images, according to some, are the result of
the visual system "attempting to make sense" of the visual
input still available to the eyes when the mind is drifting
toward sleep. Even in very low ambient light levels, light
penetrates the eyelids, making the patterns of blood flow
through them visible. This is the basis for an "interpretation"
by the visual system. The visual system may attempt to
"force" the input to correspond to, say, a geometrical
pattern, or the semblance of some object. Dream images
or memory images may intrude into such images.
Precognitive visions seen during hypnagogic imagery are
said to be particularly reliable and rarely need interpreting
because, usually, they closely resemble future events