The Evolutionary Significance of Dreaming: A Threat Simulation Perspective
Paragraph 1
It can be assumed that the brain is optimally designed for the processing of “real- world” sensory information, so that we can react in appropriate manner when confronted with environmental stimuli. Despite this fact, a large portion of mental life consists not of the processing of actual information, but rather the rehearsal of what to do when we encounter stimuli from the environment. This rehearsal and the cognitive skills involved are likely to have a strong adaptive value. Present neuroimaging data suggests that this “non-real” information is treated in a similar fashion as information processed in a real physical environment. Data from multiple neuroimaging studies support the notion that imagining something of a visual nature and manipulating that image activates our visual cortex. Actual movement does the same.
Paragraph 2
Why does this happen? By being able to practice a response or exercise a part of the brain without having to physically experience a behavior-eliciting stimulus (especially one that is potentially dangerous), we can optimize mental functioning and, ultimately, our response to an actual situation. It is well known that mental imagery techniques greatly facilitate multiple aspects of performance from sports to music. Thus, it appears advantageous to be able to create vivid representations in the mind’s eye of various scenarios, which in fact, is what dreaming entails. When a person awakes abruptly from a nightmare, the strength dream imagery has in generating both physiological and cognitive responses is evident. Even though dreams are a form of mental representation, they are generally experienced as real and the content is perceptually indistinguishable from waking perception.
Paragraph 3
It follows that imagining an event has the power to better prepare us for an actual event by physically activating comparable brain regions. Also, if this capacity to simulate an environment allows us to be optimally prepared to deal with challenges in a real environment, it should affect fitness and be naturally selected across generations. The threat-simulation hypothesis of dreaming argues that this is the purpose of dreams and the reason why dreaming has evolved. To evaluate the threat simulation theory of dreaming, it is useful to discuss it in an evolutionary context and consider whether dreaming meets the necessary requirements of evolution by natural selection; namely, genetic variation, inheritance, and differential fitness. As for the first condition, there is evidence that REM sleep is genetically varied between and within species. As the trait of physical inhibition during dreaming varies in humans, those individuals with the trait which inhibits paralysis during REM sleep seem to have been predominately removed from the current dreaming population, indicating also that the second condition of inheritance is satisfied.
Paragraph 4
When considering the third proposition of the differential fitness of dreaming in modern humans, it is important to understand that our human ancestors faced several challenges posed by interactions with conspecifics within and between groups as well as in procuring food and protecting themselves from predators. Evidence from mental imagery and dream studies suggests that rehearsal in the dream is treated as a real threat and, therefore, those individuals with such skills should have an improved ability to deal with threat, making them more likely to be the progenitors of offspring.
