A high level of environmental stimuli, such as in a visually sparse environment, can decrease alertness by reducing the need for the salience network to scan for external threats.

“And when we have a lot of things in our environment to scan, generally our level of alertness goes up. This is why environments that are very stark or have very little or very few objects in them, tend to make us feel kind of calm, because our salient network kinda shuts off.”