"Novel stimuli" refers to new or unfamiliar things that we encounter. It could be something we have never seen or experienced before, and it captures our attention because it is different from what we are used to. Full definition
Dogs appear fearful of novel stimuli or stimuli met before but that did not trigger significant reactions. (pethelpful.com)
There's biochemical research that shows the release of dopamine when we perceive novel stimuli starts to drop past the age of twenty, which makes time appear to go by more quickly. (inc.com)
It is likely the subjects in the walking group were exposed to more novel stimuli when out on their walks than those in the control group, who remained in more familiar surroundings. (marksdailyapple.com)