Dreams are subjective experiences during sleep, consisting of complex and organised images that she temporal progression (Farthing, 1992). For decades, dream investigators have tried to demystify the phenomenon of dreams and a number of theories have been established with no definitive unifying theory still. This essay aims to compare and contrast the functions and dreams of two contemporary theories of dreams: the threat simulation theory (TST) posited by Anitti Revonsuo (2001) and the information-processing theory (IPT) put forth by Rosalind Cartwright (2010). .
TST adopts the evolutionary perspective, namely the idea of natural selection, whereby in the context of a dangerous ancestral environment, organisms adopt characteristics that increased the probability of the species' survival. Hence, the TST of dreaming posits that dreaming, as an existing surviving trait, having been passed down, must serve some adaptive and useful function. TST argues that dreams simulate the dangers and perceived threats of the waking world and permits the dreamer to rehearse threat perception and to practise one's instinctual survival skills, thereby increasing overall fitness. .
IPT argues that dreams create emotionally salient experiences that reflect one's waking concerns and that are mixed with one's memories. Over time the dreams allow the dreamer to process emotional information and to work out those concerns, serving mood-regulating functions and increasing one's adaptability to the stressful events that created the waking concerns. .
This essay argues that in terms of functions, according to TST, dreams serve a natural and biological function of survival and according to IPT, dreams serve an invented and psychological function of emotional regulation. Both theories are similar in the suggestion that dreams serve an assimilatory function whereby one processes information, albeit one relating to survival threats and the other relating to waking concerns.