"For a study released last week in the journal Dreaming, [some research guy] sampled 670 people, mostly university students, two-thirds of whom were females. He had them complete surveys about the intensities of their dreams, how often their dreams contained specific themes (such as flying, being chased, suffocation, and so on), and personality traits. They also indicated how often they slept on their sides, face up (supine), or face down (prone) on a five point scale from 'never' to 'almost every time.' When he analyzed the numbers, he found that the prone sleepers, as a group, were much more likely to score highly on what he calls the Dream Motif Scale (DMS), regardless of their personality type. Motifs like 'persecution,' 'erotomania,' and 'sex' appeared significantly more frequently."