A February 2020 study (on mice) by the Flanders Institute for Biotechnology, designed to look at associative learning, said,
“Previous work suggested that novelty might activate the dopamine system in the brain. Therefore we thought that dopamine activation might also promote associative learning."
"When mice smell a novel stimulus, they get very excited and start sniffing very rapidly. This natural, spontaneous behavior provides a great readout for novelty perception."
"When we specifically blocked dopamine activation by novel stimuli in only a few trials, learning was slowed down. On the other hand, stimulating dopamine neurons during the presentation of familiar stimuli accelerated learning."