Simultaneous Contradictory Belief
People can simultaneously hold two contradictory beliefs about the same thing—one arising from intuitive, associative reasoning and the other from deliberate, rule-based reasoning—providing evidence for dual-process theories of cognition. This phenomenon, called Criterion S, is analogous to perceptual illusions like the Müller-Lyer illusion where perception and knowledge conflict.
THE IDEA
Simultaneous Contradictory Belief
Among the most compelling evidence for the hypothesis of two reasoning systems are data drawn from reasoning tasks that satisfy Criterion S: they cause people to believe two contradictory responses simultaneously. A ‘belief’ here is a propensity, feeling, or conviction that a response is appropriate even if not acted upon. For example, the statement “Technically, a whale is a mammal” can express a tension between technical classification and an informal impression; the statement alone does not establish a logical contradiction.
Analogy with Perceptual Illusions
The Müller–Lyer illusion demonstrates that perception and knowledge are distinct: we see lines of unequal length despite knowing they are equal. The conflict illustrates how a perceptual impression can persist despite contrary knowledge. The author uses it as an analogy for reasoning. Similarly, reasoning problems can elicit an intuitive response (e.g., from representativeness) and a logical response (e.g., from probability rules), both held in mind at once.
The Linda Problem (Conjunction Fallacy)
Tversky and Kahneman (1983) gave participants a description of Linda and asked them to rank probabilities. More than 80% of statistically trained participants ranked “Linda is a bank teller and active in the feminist movement” as more probable than “Linda is a bank teller,” violating the conjunction rule. Even after acknowledging the logical error, many felt a persistent intuition that the conjunction was more likely—a clear case of simultaneous contradictory belief.
Argument Strength: Inclusion Fallacy
Osherson et al. (1990) asked which argument was stronger:
- “Robins have an ulnar artery. Therefore, birds have an ulnar artery.”
- “Robins have an ulnar artery. Therefore, ostriches have an ulnar artery.”
Most chose the first, based on similarity, even though the second is logically at least as strong (since ostriches are birds). This illustrates that similarity-based intuition can coexist with logical analysis.
Syllogistic Reasoning and Belief Bias
Revlin et al. (1980) showed that belief in syllogistic conclusions varies with prior knowledge. For example, when logic and belief conflict (e.g., “No Arabian sheiks are U.S. governors” may seem empirically true, but whether it follows logically depends on the argument’s premises), many participants still endorsed the empirical belief. This demonstrates that associative memory influences reasoning even when logical rules are understood.
For Criterion S, the key is that the intuitive response persists while the person also accepts the conflicting logical response. Choosing an intuitive answer alone does not establish that both are held simultaneously.
When to use it
When evaluating arguments, recognize that your initial intuitive reaction might conflict with a more logical analysis; consider both before concluding.
In negotiations or debates, be aware of belief bias that may lead you to favor conclusions aligning with pre-existing beliefs over logical deductions.
In scientific reasoning, separate intuitive assumptions (e.g., representativeness) from empirical evidence to avoid fallacies like the conjunction fallacy.
In education, use examples like the Linda problem to demonstrate the power of heuristic thinking and the need for deliberate, rule-based reasoning.
FROM THEORY TO EVERYDAY LIFE
In practice
Linda the Bank Teller (Conjunction Fallacy)
Participants read about Linda, a philosophy major active in social justice. They ranked “Linda is a bank teller” (T) and “Linda is a bank teller and active in the feminist movement” (T&F). Over 80% rated T&F as more probable, violating the conjunction rule. Even after learning the logic, many still felt the intuitive answer was compelling.
Whale as Mammal vs. Fish
The statement “Technically, a whale is a mammal” can convey a tension between formal classification and a fish-like impression. The relevant test is whether an intuitive classification persists alongside acceptance of the technical one; resemblance by itself is not a contradictory belief.
Müller-Lyer Illusion Analogy
In the Müller-Lyer illusion, lines appear unequal despite knowledge they are equal. This simultaneous contradiction is analogous to reasoning situations where intuition and logic conflict.
A MOMENT TO REFLECT
Put it to work.
Can you recall a time when you held two contradictory beliefs about the same situation? What were the intuitive and logical responses?
How does the concept of simultaneous contradictory beliefs help you better understand cognitive biases in everyday decision-making?
Why do you think intuitive responses often persist even after you have logically disproved them? How might this affect your judgments?
References
- Simultaneous Contradictory Belief (this entry) — This text (2023)
- Tversky, A., & Kahneman, D. (1983). Extensional versus intuitive reasoning: The conjunction fallacy in probability judgment. — Tversky & Kahneman (1983)
- Osherson, D. N., et al. (1990). Category-based induction. — Osherson et al. (1990)
- Revlin, R., et al. (1980). The belief-bias effect in syllogistic reasoning. — Revlin et al. (1980)
- Sloman, S. A. (1993). Feature-based induction. — Sloman (1993)
- Sloman, S. A. (1998). Categorical inference is not just a statistical matter. — Sloman (1998)
- Lakoff, G. (1972). Hedges: A study in meaning criteria and the logic of fuzzy concepts. — Lakoff (1972)
CONTINUE THE CONVERSATION
Source texts
- Heuristics and Biases The Psychology of Intuitive Judgment (Thomas Gilovich, Dale Griffin, Daniel Kahneman)