This essay also argues that in terms meanings, both theory argue that dreams are a reflection of waking life, and are thereby continuous. However, the interpretation of the dream content are different in their emphasis according to the theories' proposed functions, though the theories overlap when real or perceived threats to survival become current waking concerns. .
Firstly, this essay explores the similarities and differences in functions according to TST and IPT. Flanigan (1995) distinguishes between two types of functions: "natural" and "invented" functions. A trait has a "natural" function when it increases one's biological survivability, while an "invented" function is something created for psychological or cultural purposes. Using this distinction, this essay argues that under TST, dreams serve a natural function, namely survival while under IPT, dreams serve an invented function, namely emotional well-being. .
TST postulates that dreams specialise in simulating threats that are perceptually and behaviourally realistic on a regular basis. This allows the dreamer to practise .
and rehearse one's threat perceptions and threat-avoidance responses (Revonsuo, 2000). Doing so enhances the probability of the dreamer's ability to negotiate similar real life threats efficiently and successfully (Revonsuo, 2000, p. 882).
Revonsuo (2000) cites studies that demonstrated how mental imagery can improve the neural mechanisms that generate actual actions (Decety, 1996), and argues that such virtual reality practice and mental training during dreams constitute realistic simulations in a safe environment that can enhance perceptual and motor skills and sharpen real life responses to similar threats should they occur. This is similar to how pilots use virtual reality for flight training to prepare them for actual flights. .
Zadar, Desjardins and Marcotte's (2006) study on recurrent dreams among 266 subjects supports the TST argument of threat simulation.
