Normative vs. Descriptive Models of Decision Making

The Axioms of Choice

For a person to be considered "instrumentally rational," their preferences must follow specific logical patterns known as the axioms of choice. These axioms ensure that decisions are consistent and not manipulated by irrelevant context.

• Transitivity: If you prefer option $A$ over $B$, and $B$ over $C$, you must prefer $A$ over $C$. Violating this can lead to a "money pump," where a person is tricked into a cycle of losing wealth through inconsistent trades.
• The Sure-Thing Principle (Dominance Axiom): Your preference between two options should not change based on whether an unrelated event $X$ occurs or not.
• Independence Axiom: If an outcome is identical across two different options, that specific state should be ignored in the decision process.
• Regularity Principle: Adding or removing a third option should not change your relative preference between the two original options.

Descriptive Models: Why Humans Deviate

While normative models tell us how we should behave, descriptive models show that humans frequently violate the axioms above due to cognitive biases and mental shortcuts.

Framing and Loss Aversion

One of the most powerful ways humans deviate from rationality is through framing effects. This occurs when the way information is presented—rather than the information itself—changes the choice made. Much of this is driven by loss aversion, the psychological tendency to feel the pain of a loss much more intensely than the joy of an equivalent gain.

This leads to several specific phenomena:

• The Endowment Effect: People tend to overvalue items simply because they already own them.
• Status Quo Bias: A tendency to prefer things to stay as they are, often because changing the current state is perceived as a potential loss.

Procedural Invariance and Constructed Preferences

In a perfectly rational world, procedural invariance would hold: your preference shouldn't change based on how you are asked to make a choice. However, humans often experience preference reversals, where they choose differently depending on the wording or method of the question.

Modern psychology suggests this happens because of the Constructed Preference View. Instead of having fixed, stable preferences waiting to be "discovered," humans may actually construct their preferences "online"—meaning they are built in real-time during the decision process using contextual cues from the environment.

Dual-Process Theory: The Engine of Decision Making

To explain why these deviations occur, researchers often point to Dual-Process Theory, which suggests the brain uses two distinct modes of cognition:

1. Type 1 Processing: Fast, automatic, and intuitive. It is the "adaptive unconscious" that uses heuristics (mental shortcuts) to make quick decisions.
2. Type 2 Processing: Slow, analytic, and computationally expensive. This is the conscious, rule-based thinking required for complex logic and overriding impulsive Type 1 responses.

When we face a difficult problem, we often engage in attribute substitution, a Type 1 trick where we replace a hard question (e.g., "How likely is this complex medical diagnosis?") with an easier one (e.g., "How vivid is the description of the symptoms?").

Implications: Paternalism and Improvement

Understanding these models has real-world consequences for policy. Some advocate for Libertarian Paternalism, a philosophy suggesting that governments should "nudge" people toward better choices (the paternalistic part) while still preserving their absolute freedom of choice (the libertarian part). This is done by controlling the "default" options or the way choices are framed, exploiting our natural sensitivity to context.

On an individual level, we can improve our own instrumental rationality by:

• Learning the formal rules of logic and decision theory.
• Deliberately reframing problems to avoid being trapped by a single perspective.
• Being aware of outcome bias—the tendency to judge the quality of a decision based on its result rather than the process used to make it.