better able to detect and quickly process “something different”— either danger or opportunity — were more likely to survive and pass on their genes. There was a payoff from waiting patiently for some movement in the trees that signaled “danger,” or noticing the sound of a particular bird that circled a tree with a beehive full of honey, etc.
Today we know it’s the neurotransmitter dopamine which causes the feelings of pleasure and motivation for “more”. Dopamine regulates our vigilance of noticing anything different than the usual in our homes, our environments, and the systems we interact with. Without dopamine we wouldn’t be curious or motivated to even get out of bed. Experimental removal of dopamine receptor genes in animals causes them to reduce exploratory behavior related to resource acquisition 35 . Dopamine activation is also linked with addictive, impulsive activity in numerous species. But of most relevance to modern human
society, dopamine is released within the brain not only in response to stimuli an organism finds rewarding, but also to those events which predict rewards. A famous study involved thirsty monkeys who waited for a tone followed by a squirt of fruit juice into their mouths. After a regimen of fixed, steady amounts of juice, the volume of juice was doubled without warning which caused the rate of neuron firing to go from 3 per second to 80 per second. Whoa, where did that juice come from — it was tasty!! But after several trials and as this new magnitude of reward was “habituated to”, after hearing the familiar sound, the neuron firing rate returned to the baseline of three firings per second. The monkeys had gotten used to what was coming . It was the same amount of fruit juice as before, but since double-juice was now expected , it no longer caused the feel-good brain release of dopamine 36 . When exposed to novel stimuli, high levels of curiosity (dopamine) are generated, but it is the unexpected reward that causes their activation. Think about how our core brain responds to novelty in our modern world. If your smart phone announces an incoming email, a tiny hit of dopamine motivates you to see who it was from, but the actual reading of the email
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