Daniel Kahneman's theory of two thinking systems - System 1 and System 2 - can help explain user trust and decision making. System 1 is fast, automatic, and emotional while System 2 is slow, effortful, and logical. To build user trust, designers should focus on social proof, aesthetics, usability, documentation, consistency, transparency around data use and security, and only request necessary permissions from users. Establishing an ongoing relationship with users through a quality experience over time also helps develop trust.