"When our brain gets used to something, it displays less and less of a response each time it sees it—a phenomenon called repetition suppression. The more familiar something is, the less neural energy we spend on it.
But, there is a problem with a lack of surprise. The better we understand something, the less effort we put into thinking about it. Familiarity breeds indifference. Repetition suppression sets in and our attention wanes. In fact, the neurotransmitter system involved in reward is tied to the level of surprise: rewards delivered at regular, predictable times yield a lot less activity in the brain than the same rewards delivered at random, unpredictable times. Surprise gratifies.
Brains seek a balance between exploiting the knowledge we’ve earned and exploring new surprises. In developing over eons, brains have gotten this tension well balanced – an exploration/exploitation tradeoff that strikes the balance between flexibility and rigor. Too much predictability and we tune out; too much surprise and we become disoriented. We live in a constant tug-of-war between routine and novelty. Creativity lies within that tension."