They know exactly what they need to buy.
They shop according to a plan.
By the time he or she reaches the check-out counter, the customer is feeling pleased and relaxed because the task of shopping is finished.
In this Happy mood, the customer sees an attractive display of inexpensive goods that were not on her shopping list.
Now she feels like buying something just for her own pleasure and enjoyment.
Many customers buy from these displays of products near the check-out. Counter, and this is exactly what the owner of the supermarket hopes they will do.