The Interest-First Test
Decode any moral position by asking whose fitness interests it serves first
- Difficulty
- Easy
- Time to result
- ~ongoing to results
- Steps
- 6
- Confidence
- 60%
Kurzban's diagnostic inverts how we usually read moral claims. Instead of starting with a person's stated principle ('sanctity of life', 'bodily autonomy'), you first ask where their fitness or material interests lie, then treat the stated principle as the marketing wrapper. The mechanism rests on evolutionary logic: humans who advocated rules that advanced their own reproductive success out-competed those who didn't, so we are built to favour rules that benefit us while narrating them as high principle. Self-deception is a feature — not consciously knowing the selfish motive stops it leaking out. You apply the test by mapping the interest a position protects, checking whether unrelated positions cluster in a self-serving way, and probing with hypotheticals that pull principle apart from interest. Positions that survive a real personal cost are the rare genuine ones.
Origin
Developed by evolutionary psychologist Rob Kurzban with collaborator Jason Weeden, who tested it on abortion attitudes and found that people's monogamous vs promiscuous mating strategies predicted their stance better than their stated moral philosophy.
Core principles
- 01Stated principles are downstream of interests, not the other way round
- 02People are designed to advocate rules that advance their reproductive and material interests
- 03Self-deception hides the real motive so the game doesn't leak out
- 04The most Angelic-sounding justification is usually the least honest one
- 05Genuine principle exists but is rare — it shows up when someone pays a cost against their own interest
How to run it
- 1
Suspend the stated reason
When someone declares a moral position, resist immediately weighing the reason they give. Treat it as a claim to be explained, not accepted.
Pro tip The more noble and universal the language ('I believe in the sanctity of life'), the more it may be doing PR work.
- 2
Locate the interest
Ask what lifestyle, status, mating strategy, or material stake the position protects or advances for the person holding it.
Pro tip Kurzban's frame: 'the first place you want to look is not to their overarching principles but where their fitness interest lies.'
- 3
Check the cluster
See whether their position on one issue predicts their stance on a seemingly unrelated one. Tight clustering that all points the same self-serving way is a tell that interest, not principle, is driving.
Pro tip In their study, recreational-drug attitudes predicted abortion attitudes via a shared promiscuous-lifestyle strategy.
- 4
Probe with a splitting hypothetical
Construct a scenario that separates the stated principle from the person's interest and watch whether they hold the line. Contradictions expose the real driver.
Pro tip Ask the rape-exception question of someone claiming 'life begins at conception' — the exception reveals the principle isn't the true reason.
Watch out People rarely enjoy this; use it to understand, not to ambush.
- 5
Reserve credit for costly principle
Mark a position as genuinely principled only when the holder pays a real cost for it against their own interest — like civil-rights advocates fighting for groups they didn't belong to.
- 6
Turn the test on yourself
Apply the same lens inward. Because self-deception is adaptive, assume you don't fully know your own motives, and use contradictions you catch in yourself to find where a principle is really an interest.
Pro tip The magic happens 'when you catch yourself in a contradiction' — that's the signal to trace a belief back to its true source.
In the wild
Kurzban and Weeden hypothesised that abortion stances track mating strategy rather than moral philosophy. People living a more promiscuous strategy benefit from low-cost 'mistakes', so they favour access; people in monogamous relationships benefit from making straying costly, so they oppose it. Skeptical at first, Kurzban gathered data and found attitudes lined up with lifestyle interests — and that unrelated items like recreational-drug attitudes predicted abortion stance through the same underlying strategy.
→ A predictive model of moral attitudes grounded in interest, not stated principle.
To test whether 'life begins at conception' is the real reason behind an anti-abortion stance, Kurzban applies a splitting hypothetical: ask whether a 13-year-old who was the product of rape should therefore be killed. The person says of course not — revealing that the stated principle isn't actually load-bearing and some other motive is doing the work.
→ A single hypothetical surfaces the gap between stated principle and true driver.
Common mistakes
Treating cynicism as the whole story
The test finds hidden interest, but genuinely principled actors exist — people who pay a cost against their own interest. Assuming everyone is purely self-serving misreads the heroes.
Only aiming the lens outward
The hardest and most valuable application is on yourself. Skipping the inward pass keeps your own motivated reasoning invisible.
Confusing the wrapper for the reason
Accepting the most noble-sounding justification at face value is exactly the failure the test exists to prevent.
Is it for you?
Best for
Anyone parsing contested political, ethical, or workplace positions who wants to see the incentive underneath the argument.
Not ideal for
Situations where charitable good-faith engagement matters more than exposing hidden motives.
From the transcript
“if you want to understand people's kind of moral commitments the first place you want to look is not to their overarching principles but you…”
“what we should be aware of when people tell us what their positions are is to first ask this question okay well where do their…”
“the real magic happens when you catch yourself in a contradiction”
From the episode
The Evolutionary Psychology Of Human Morality - Rob Kurzban - #796
Rob Kurzban