The basal ganglia in the brain creates habits. People unable to make new memories due to brain damage can still make new habits. For instance, they can take a walk around a block after moving even though they cannot point out their house or give directions during the walk.
Making a new habit is called chunking. Chunking makes it so a process can be done without applying higher order thinking. The brain is free to think about other things.
To make a new habit a cue is needed for when to start a process. A similar routine must be able to be followed each time. There must be a reward at the end of the process.
Advertisers have known about the cues and rewards for over a century. The reward in product use must convince the consumer the product is working. For instance toothpastes add foaming and tingling agents that don’t add to the cleaning. Shampoos also add foaming agents. Proctor and Gamble had to add more perfume to Febreze (an odor killer). They also marketed spraying Febreze as the reward at the end of cleaning.
The signals a product works can create a craving. If a toothpaste does not tingle as expected consumers will worry it isn’t working or maybe think they forgot to brush.