Question

American shoppers usually do not like it when a store is so cramped that the customers may touch one another while shopping. when the _____ occurs, customers may decide to leave without making a purchase.

Answer 1

Whe the . butt- brush effect occurs, the purchase is very unlikely to happen.
The butt-Brush effect is a theory that first coined by an anthropologist named Paco Underhill. 
This effect views that customers are far less likely to make a purchase if their physical spaces are being threaten (especially if the buyers are females)

Answer 2

American shoppers usually do not like it when a store is so cramped that the customers may touch one another while shopping. When the Butt Brush Effect occurs, customers decide to leave without making a purchase.

In days of big sales, stores are most likely to be occupied by large number of people and people may be pushed by other people, or table, or any piece of merchandise from the back. People, especially ladies do not like it at all. So they prefer to leave the shop instead of continuing shopping. This effect is called as the Butt Brush Effect.