Understanding human psychology is a crucial part of creating effective advertising. It allows us to understand consumer behavior, needs, and motivations, and enables us to design campaigns that resonate with our target audience.

Here is a list of key principles and how they are applied in digital advertising:

1. The Principle of Reciprocity: 

This principle suggests that people feel obliged to give back when they receive something. This principle comes from social psychology and it refers to our innate desire to return favors in order to maintain balance in our relationships. In advertising, giving something to consumers first—like a free sample or valuable information—can induce a sense of obligation to give something back. E-commerce platforms can offer personalized discounts or gifts based on a customer's browsing history or past purchases. This makes the act of giving feel more personal and increases the likelihood of reciprocation. 

2. The Scarcity Principle: 

Rooted in economic theory as well as psychology, this principle plays on the fear of missing out (FOMO). When we perceive something as scarce, we value it more because we believe it's in high demand. Limited-time offers or limited stock can create a sense of urgency to buy. Online retailers often use real-time stock indicators and countdown timers for limited-time offers. These dynamic elements create a sense of urgency that can motivate immediate action.

3. Social Proof: 

This concept is based on conformity, a powerful social force discovered through psychological experiments. We're social creatures, and we often look to others for cues on how to think, feel, and act. Advertisers leverage this by showing us that others like us have approved of their product or service. Social media platforms are perfect for showcasing user-generated content, reviews, and testimonials. For example, Instagram stories featuring customers using a product can serve as powerful social proof.

4. The Authority Principle: 

People tend to follow authority figures. The famous Milgram experiment demonstrated just how much sway authority figures hold over us. Advertisers use this principle when they include expert opinions, celebrity endorsements, or other authoritative figures in their ads. Live webinars or Q&A sessions with industry experts or influencers can be hosted on platforms like YouTube or Facebook. These live interactions increase perceived authority and credibility.

5. The Consistency Principle: 

People like to act consistently with their values and past decisions. Reminding customers of their past purchases or preferences can encourage repeat business. Cognitive dissonance theory suggests that we strive for consistency in our beliefs, attitudes, and behaviors. Once we've made a choice or taken a stand, we'll encounter personal and interpersonal pressure to behave consistently with that commitment. Advertisers remind us of our past actions to encourage consistent future actions. Email marketing automation tools can send reminders to customers about items left in their cart, nudging them towards completing the purchase. This leverages their initial interest (consistency) and can increase conversion rates.

6. The Liking Principle: 

Interpersonal attraction research tells us that we're more likely to say yes to people we like. Brands strive to be likable and to connect with their customers on a personal level to drive loyalty and sales. Brands can use AI-powered chatbots to interact with customers in a friendly, personable manner. This not only improves customer service but also helps build a likable brand image.

Remember, while technology provides us with powerful tools to apply these principles, it's crucial to use them responsibly and ethically, always prioritizing the value and respect for the customer.