In the 1960s Ian Oswald of the University of Edinburgh conducted a study intended to test whether people could fall asleep under extremely disturbing conditions. Three volunteers had their eyelids taped, so their eyes would stay open. Flashing lights were placed in front of their open eyes. He also had attached electrodes to their legs that administered electric shocks. Finally, music was played at a high volume. All of the volunteers eventually fell asleep. Oswald concluded that their brains adapted to the repetitive and monotonous nature of the stimulants.
Despite the unethical nature of the study, Oswald did indeed uncover an important feature of the brain. Repetitive stimulation, even of an extreme kind, eventually makes the brain tune out. The brain simply stops paying attention to the stimulus and this enables it to engage in other activities.
Repetition is important in wiring your brain when you learn new things. Repetition helps your brain form new connections between synapses. As the old saying has it, “practice makes perfect”. A famous study of London taxicab and bus drivers found that the regions of the brain used for memory and spatial navigation were significantly larger in the cab drivers. The obvious conclusion was that cab drivers have to remember the routes of the city, whereas the bus drivers are following a set route every day.
Despite the importance of repetitive practice in learning, when a stimulus is just triggering activity in networks that are already laid down, the brain prefers to spend its energy elsewhere. When exposed to a stimulus repeated over and over again, the brain reacts the way the brains of the bus drivers reacted. It does not make new neural connections or build new gray matter, it simply tunes out. We are very familiar with this phenomenon when taking the same route to work every day. Though our brains keep track of the road, most of its conscious focus is elsewhere.
This insight can be used in resolving emotional conflicts and eliminating emotional pain. Instead of letting intruding thoughts penetrate your awareness without being in control of them, take control and force yourself to think these thoughts or expose yourself to physical reminders at regular intervals. Over time the brain will start paying less attention to the thoughts or physical reminders and soon enough it will be less inclined to bring the constantly repeated stimulus to your attention when you least expect it.