What this means is that the amount of dopamine released into the nucleus accumbens does not depend on the absolute amount of reward an animal receives, but on how unexpected it is. This further suggests that we enjoy and crave environments in which we receive unexpected rewards; in other words, we enjoy risk. Put another way, dopamine spikes with information; and it acts as a learning signal, making us remember what we have just discovered. Some neuroscientists, such as Jon Horvitz at Columbia and Peter Redgrave at Sheffield, have even gone beyond the dopamine-as-predictor-of-pleasure idea and
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