Reference Guide
Foundational concepts to help you understand decision science. Each term is defined with its original academic source.
Core Frameworks
Dual Process Theory
The distinction between fast, intuitive System 1 thinking and slow, deliberate System 2 thinking. Most decisions are made by System 1.
Kahneman, 2011
Prospect Theory
People evaluate outcomes relative to a reference point, and losses weigh roughly twice as heavily as equivalent gains.
Kahneman & Tversky, 1979
Nudge Theory
Any aspect of choice architecture that alters behaviour in a predictable way without forbidding options or significantly changing economic incentives.
Thaler & Sunstein, 2008
COM-B Model
Behaviour requires three conditions: Capability (physical & psychological), Opportunity (social & physical), and Motivation (automatic & reflective).
Michie, van Stralen & West, 2011
Fogg Behaviour Model
Behaviour happens when three elements converge at the same moment: Motivation, Ability, and a Prompt (B = MAP).
Fogg, 2009
Choice Architecture
Default Effect
People tend to accept pre-set options. Organ donation rates vary from 4% to 100% across countries based solely on whether the default is opt-in or opt-out.
Johnson & Goldstein, 2003
Choice Overload
When faced with too many options, people are less likely to make a choice and less satisfied when they do. The classic jam study showed 30% vs 3% purchase rates.
Iyengar & Lepper, 2000
Libertarian Paternalism
The philosophical framework for nudging: helping people make better choices (paternalism) while preserving freedom of choice (libertarian).
Thaler & Sunstein, 2003
Sludge
Excessive friction in processes that discourages beneficial actions. The opposite of a nudge — it makes good choices harder.
Sunstein, 2019
Measurement & Method
Randomised Controlled Trial (RCT)
The gold standard for measuring causal effects of behavioural interventions. Participants are randomly assigned to treatment and control groups.
Fisher, 1935
Applied Information Economics
A framework for measuring the value of information and reducing uncertainty in decision-making, even for "unmeasurable" intangibles.
Hubbard, 2007
Effect Size
A quantitative measure of the magnitude of an experimental effect. Cohen's d of 0.2 is small, 0.5 is medium, 0.8 is large.
Cohen, 1988
Pre-Registration
Publicly registering study hypotheses and analysis plans before data collection to prevent p-hacking and HARKing.
Nosek et al., 2018
Organisational Behaviour
Psychological Safety
A shared belief that the team is safe for interpersonal risk-taking. Teams with high psychological safety learn from mistakes rather than hiding them.
Edmondson, 1999
Implementation Intentions
"If-then" plans that link situations to responses: "If situation X arises, then I will do Y." Doubles to triples goal achievement rates.
Gollwitzer, 1999
Switch Framework
For organisational change: Direct the Rider (rational mind), Motivate the Elephant (emotional mind), Shape the Path (environment).
Heath & Heath, 2010
Moral Foundations Theory
Six innate moral foundations — Care, Fairness, Loyalty, Authority, Sanctity, Liberty — that shape how people evaluate ethical situations.
Haidt, 2012