The principle library behind every simulation.

People look to the actions and approval of others to decide what is correct or worth doing, especially under uncertainty.

Cialdini, Influence: The Psychology of Persuasion (2021)

Opportunities seem more valuable when their availability is limited.

Cialdini, Influence: The Psychology of Persuasion (2021)

People defer to credible experts, credentials, or recognized sources when deciding what to trust.

Cialdini, Influence: The Psychology of Persuasion (2021)

People feel obligated to return a favor, so a free sample or piece of value makes them more willing to act.

Cialdini, Influence: The Psychology of Persuasion (2021)

Once people commit to a small action, they feel pressure to behave consistently with that commitment in later, bigger decisions.

Cialdini, Influence: The Psychology of Persuasion (2021)

A real time constraint, such as a deadline or an expiring offer, prompts immediate action instead of deferral.

Cialdini, Influence: The Psychology of Persuasion (2021)

People weigh the pain of a potential loss more heavily than the pleasure of an equivalent gain, which makes "don't miss out" framing more motivating than "gain this."

Kahneman & Tversky, Prospect Theory (1979)

The first number or option a person sees becomes a reference point that skews how they judge everything after it.

Tversky & Kahneman, Judgment Under Uncertainty (1974)

The same offer feels different depending on how it is worded, so a gain frame and a loss frame can lead to different choices even when the underlying facts are identical.

Tversky & Kahneman, The Framing of Decisions and the Psychology of Choice (1981)

People value something more once they feel it is already theirs, which is why free trials, samples, and "your plan" framing increase commitment.

Kahneman, Knetsch & Thaler (1991)

People default to the current or familiar option and need a clear reason to switch away from it.

Samuelson & Zeckhauser, Status Quo Bias in Decision Making (1988)

Too many options increases decision difficulty and anxiety, often leading people to delay or avoid deciding at all.

Schwartz, The Paradox of Choice (2004)

Adding a deliberately less-attractive third option shifts preference toward one of the original two by making it look like the better deal.

Huber, Payne & Puto, Adding Asymmetrically Dominated Alternatives (1982)

The more options you put in front of someone, the longer they take to decide, so fewer, clearer choices lead to faster action.

Hick (1952); Hyman (1953)

People disengage when a page demands too much mental effort to parse, so clarity and brevity convert better than density.

Sweller, Cognitive Load During Problem Solving (1988)

People remember the first and last items in a sequence better than the middle, so the most important points belong at the top and the bottom of the page.

Ebbinghaus (1885); Murdock (1962)

People remember an experience mainly by its most intense moment and how it ended, so a strong closing section shapes the overall impression.

Kahneman, Fredrickson, Schreiber & Redelmeier (1993)

A strong positive impression in one area, such as clean design or a polished hero section, spills over into how people judge everything else.

Thorndike, A Constant Error in Psychological Ratings (1920)

People tend to prefer things they have seen before, so repeated, consistent exposure to a brand or message builds comfort and trust over time.

Zajonc, Attitudinal Effects of Mere Exposure (1968)

People push harder to finish as they get closer to a goal, so showing progress through a multi-step form or signup increases completion.

Hull (1932); Kivetz, Urminsky & Zheng (2006)