According to the Daily Mail:
Prone sleepers reported feeling sensations related to ‘sex’ and ‘persecution’ more frequently than anyone else.
Among the other racy motifs that came up for them were ‘being tied up’, ‘being locked up’ and ‘unable to move’.
The researchers said that the increase in sexy thoughts could be because when you are on your front you do not get so much air, so your mind was imagining being constricted when you sleep.
The research was carried out by researcher Calvin Kai-Ching Yu, of Shue Yan University in Hong Kong.
He spoke to 670 students, two-thirds of whom were female, and asked them to fill out surveys about their dreams.
Kai-Ching Yu said: ‘This study provides the evidence that dream experiences, and in particular dream content, can be influenced by body posture during sleep.
‘I believe that the brain during sleep is not at all totally detached from the external world, and stimuli, including those stemming from the environment, are probably incorporated into dream content more often than people observe or are aware of.
‘The unconscious brains of the dreamers try to make sense, and even make use of, the external stimuli’.
NO! I'm having perverse dreams and “sensations” because the weight of my body is sandwiching my cock into the mattress and that gives me a boner and when I get a boner my brain goes into beast mode and starts thinking about how it's going to kill the boner. It has nothing to do with the lack of air I'm receiving from the “prone” position. Now give me $250K research grant to confirm that theory.