What is an impulse purchase?
A general definition
LottoStocks defines an impulse purchase as:
a purchase of a good or service made without great consideration given beforehand as to either the consequences that will arise out of or the value of the purchase.
An academic explanation
The following is from Suresh Ramanathan and Geeta Menon from their treatise The Dynamics of Impulsive Behavior: Construct versus Goal Activation Effects on Memory, Evaluations and Choice:
"Most people believe that they are capable of controlling their impulses and desires. Yet, every now and then, the sweater in the window that shrieks out “buy me!” (Rook, 1987) or the feeling “it was like I was on automatic” (O’Guinn & Faber, 1989) challenges these beliefs. For instance, one definition of the buying impulse has been derived from the Greek word akrasia, or “weakness of will” (Wood 1998). Wood defines akratic impulses as unplanned purchases, undertaken with little or no deliberation, accompanied by affective mood states that furthermore are not compelled, and that, finally, are against a buyer’s better judgment. Impulses have also been defined as “desires” that compete with an individual’s “willpower” (Hoch and Loewenstein 1991).
"The most widely cited definition of impulse buying is attributed to Rook (1987), who characterized such actions as those where “a consumer experiences a sudden, often powerful and persistent urge to buy something immediately.” This urge materializes as a buying stimulus that is spontaneous , kinetic , psychologically arousing, immediate and “primary” (Rook 1987). This definition actually encompasses two psychological phenomena – a sudden felt urge and an immediate action. Further, it defines impulsive behavior as a strong and immediate affective reaction. In other words, spontaneous affect drives behavior; e.g., seeing ice cream in the supermarket freezer evokes an immediate visceral and affective reaction in the form of an urge that then causes the person to pick it up and add it to her shopping cart. Recent studies conducted by Shiv and Fedorikhin (1999) also support this notion."
The impulse purchase factor is highest when you have (1) just made a purchase...and that purchase was of a basic necessity that did not take a lot of thought in order to make the purchase...so the mind is in reflexive mode to spend without much contemplation; and (2) have cash in hand...that is, change from a purchase. Impulse purchases of low-priced, small or "spare-change" items are most common. Often, a purchase of a basic necessity good or service has been made immediately prior to the impulse purchase.