In the field of psychology, the subfield of oneirology (/ɒnɪˈrɒlədʒi/; from Ancient Greek ὄνειρον, oneiron, "dream"; and -λογία, -logia, "the study of") is the scientific study of dreams.

Some dream researchers are using a technique called neural decoding to both decipher and even predict visual imagery in dreams, based on observations of brain activity. Dreams are a compelling area of research for scientists, in part because there's still so much to learn about how, and why, we dream.

Most crucially, the length of dream reports can vary greatly from group to group or person to person. This is a problem because longer reports are likely to have more of most things in them, although one study showed that the relationship is not monotonic for all types of categories.