Retailers have invested billions of dollars into understanding what makes customers tick. It often seems there are just as many schools of thought to explain why people behave the way they do in terms of buying products.

It’s often helpful for marketers to take a step back to consider broader theories of human conduct. With that in mind, here are four consumer behavior theories relevant to marketing teams today.

1. Theory of Reasoned Action

This theory, which emerged in the late 1960s, suggests people are rational beings who will act in their own best interests — aiming to achieve specific outcomes that benefit them. According to this theory it’s very important for marketers to create a tangible link between cause and effect: Buying X product will get you Y result.

2. Motivation-Need Theory

This theory harkens back to Maslow’s hierarchy of needs.

Listed in order, from most important to least important, these are:

• Physiological: Sleep, food, water, breathing, sex, homeostasis, excretion
• Safety: Security of body, mind, employment, resources, family, health
• Love/belonging: Family, friendship, sexual intimacy
• Esteem: Respect from/of others, confidence, self-esteem, achievement
• Self–actualization: Creativity, problem solving, morality, spontaneity

As one marketing expert writes for Forbes, marketers can use this theory to establish needs by level for audience segments — then effectively communicate to address these needs. Of course, customers for many products will be chasing perceived needs as opposed to needs directly tied into survival; it all depends where target customers tend to fall on the pyramid.

3. Hawkins Stern Impulse Buying Theory

Anyone who’s ever seen something they wanted and purchased it without much thought will understand what this theory is saying firsthand. According to Hawkins Stern, people buy products “based on external stimuli” — sometimes without much evaluation or rational thought at all. The motivation for a purchase could be as simple as seeing something and adding it your cart, like a magazine in the grocery store checkout line.

When marketers give credence to the idea not every purchase may be rational and deeply considered, they can find opportunities to capitalize on impulsive purchases — like making targeted cross-selling recommendations of less expensive products right before a buyer finalizes a purchase. There just may be something to the idea buyers will say, “Well, why not?” and add it to their tabs.

4. Freudian Motivation Theory

Sigmund Freud is a somewhat controversial figure in the world of psychology — with some singing his praises and others writing off his theories as outdated. Still, the Freudian Motivation Theory does posit some interesting ideas regarding the reasons people purchase what they do.

According to Freud, unconscious desires and motivations are just as important as conscious needs. This theory implores marketers to dig into the emotional response their products evoke.

Here’s an example from Investopedia: Someone buying furniture for their first house or apartment may be looking for more than just aesthetically pleasing and functional furniture; they could actually be seeking out a warm, cozy sense of home. The furniture then represents loftier ideas like safety, independence and comfort.

The one thing all these theories have in common is trying to drill down to the core of how people decide to buy something. While these theories about why no doubt are compelling, it’s also highly important to analyze the ways in which customers are actually behaving. Using the advanced marketing analytics available today, teams can extract patterns and insights from within millions of data points — shedding light on how consumers act and which factors affect engagement and sales.

The great thing about using theories of consumer behavior in combination with analytics is they all bring a new perspective to the table, helping marketers look at data from different angles.