subject see the world upside down. But, as the brain adjusts to the change, the world appears "normal." In some extreme experiments, psychologists have tested to see if a pilot can fly a plane with altered vision. All of the pilots that were fitted with the goggles that altered their vision were able to safely navigate the aircraft with ease. Visual Adaptation is considered to be the cause of perceptual phenomena like afterimages and the motion aftereffect. In the absence of fixational eye movements, visual perception may fade out or disappear due to neural adaptation. (See Adaptation (eye)). When an observer's visual stream adapts to a single direction of real motion, imagined motion can be perceived at various speeds. If the imagined motion is in the same direction as that experienced during adaptation, imagined speed is slowed; when imagined motion is in the opposite direction, its speed is increased; when adaptation and imagined motions are orthogonal, imagined speed is unaffected. Studies using magnetoencephalography (MEG) have demonstrated that subjects exposed to a repeated visual stimulus at brief intervals become attenuated to the stimulus in comparison to the initial stimulus. The results revealed that visual responses to the repeated compared with novel stimulus showed a significant reduction in both activation strength and peak latency but not in the duration of neural processing. Although motion and images are extremely important regarding adaptation, the most important adaptation is adjusting to brightness levels. On entering a dark room or a very brightly lit room it takes a little while to adjust to the different levels. Adjusting to brightness levels allows mammals to detect changes in their surrounding. This is called dark adaptation. Auditory Auditory adaptation, as perceptual adaptation with other senses, is the process by which individuals adapt to sounds and noises. As research has shown, as time progresses, individuals tend to adapt to sounds and tend to distinguish them less frequently after a while. Sensory adaptation tends to blend sounds into one, variable sound, rather than having several separate sounds as a series. Moreover, after repeated perception, individuals tend to adapt to sounds to the point where they no longer consciously perceive it, or rather, "block it out". An individual that lives close to the train tracks, will eventually stop noticing the sounds of passing trains. Similarly, individuals living in larger cities no longer notice traffic sounds after a while. Moving to a completely