 How do the blind dream? Images, ideas, emotions and sensations. A dream. Whether it's short or long, whether you can or can't remember it, everyone dreams. But what do people that can't see see in their dreams? And how do they dream? To start, here are some facts about dreams. Dreams are usually phantasmagoric. People, places, events and objects tend to merge into one another in a confusing manner. The most common emotion experienced in dreams is anxiety and other negative emotions, much more prevalent than positive ones. The vast majority of people dream in colour, but if you watched monochrome television growing up, you are more likely to dream in black and white. Only around 10% of dreams are sexual in nature, although the percentage is higher among adolescents. But what about individuals that cannot see? Individuals who have been blind since birth, congenital blindness, or very early in childhood usually have no images in their dreams. However, this varies from person to person. Some studies conclude that if a person loses his or her sight before the age of five, they will almost never have images in dreams. Interestingly enough, the congenitally blind have cortical areas responsible for visual representations activated during dreaming. These activations are manifested instead through the senses of hearing, touch, taste and smell. For those who go blind in middle childhood, it seems that the situation can go either way. Dreams are reported as both visual and non-visual at times. Initially after blindness, visuals may be present, but then slowly fade or disappear altogether after time. Those who become blind later in life continue to experience some images in their dreams. What do the blind dream about? In a study published in February 2014 by a group of Danish researchers in sleep medicine, 18% of the blind participants, both congenital and later onset, reported tasting in at least one dream. 30% of the blind reported smelling in at least one dream. 70% of the blind reported a touch, sensations. 86% of the blind reported hearing. When looking solely at the congenitally blind group, 26% tasted, 40% smelled, 67% touched and 93% heard in at least one dream. Despite these sensory differences, the content of dreams is not much different in the blind and the sighted. Both groups reported about the same number of social interactions, successes and failures in their dreams. However, the blind group had a lot more nightmares. 25% compared with only 7% of the later onset blind group and 6% of the sighted control group. This difference held even after the researchers controlled for sleep quality, which is generally poorer among the blind. This increased number of nightmares could be because of evolution, where nightmares can be seen as threat simulations as a mentally harmless way that the human mind can adapt to the threats of life. Basically, the nightmares give someone an opportunity to rehearse the threat perception with the avoidance of having to actually cope with the threat. Oftentimes, a recurring theme in the dreams of many blind people, congenital or not, is transportation, possibly because that is something that often gives them trouble in real life. This makes sense because for the blind, most frequently reported nightmares included events such as getting lost, being hit by an unseen car, falling into manholes and losing their guide dog. A greater number of recurring threats than the sighted in everyday life, hence the increased number of nightmares. Although the other senses take over in dreams for the blind, especially for the congenitally blind, a 2003 study conducted in the EEG-slash-sleep laboratory, Centro de estudias egas manis faculdade de medicina des labor, in Portugal showed that when it came to visually recalling and recreating a dream, there was no statistical difference between the blind and the sighted. When asked to create a graphical representation of a dream in the form of a drawing, blind subjects were able to create drawings of dream scenes that accurately represented the generic scenes they had verbally described earlier. Between the calculated mean for complexity and the content of the drawings, no statistical differences were found between the groups. In both groups, landscapes were present in 70% of the drawings, objects in 90%, human figures in 10%. So what does this mean? Although the blind can't see with their eyes as the sighted can, they see in their dreams through other heightened senses and sometimes can even see images, if not congenitally blind. They dream about the same things as the sighted, although they have nightmares more frequently. And the most surprising finding? The lack of the sense of sight in dreams does not hinder the blind from describing nor representing their dreams graphically, with accuracy and complexity being statistically the same as the sighted control group.