How people can spot “Moses illusions” faster than we think

What is it about?

When people hear the question “How many animals did Moses take on the Ark?”, most answer “Two,” even though it was Noah, not Moses, in the biblical story. This classic mistake is known as the Moses illusion (or semantic illusions). It seems to show that people rely on fast, automatic thinking that skips over small details, and that only careful reflection can catch the error. Our study challenges this idea. Across three experiments, we asked people to answer illusory questions quickly while under time pressure and distraction, and then again after more reflection. Surprisingly, many people correctly noticed the problem right away, without needing extra time. Even when people gave the wrong answer, their confidence was lower, showing that they felt something was off. These findings suggest that our intuitions are not purely blind or careless: people can sometimes detect these illusions instantly and automatically.

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Photo by Fr. Barry Braum on Unsplash

Photo by Fr. Barry Braum on Unsplash

Why is it important?

This work reshapes how psychologists think about “fast and slow” thinking. The classic dual-process model assumes that detecting an error requires slow, deliberate reasoning. We show that, for language understanding, even our quick, intuitive thinking can be sensitive to meaning conflicts. This means that some people intuitively detect semantic mistakes like the Moses illusion without deliberate analysis. The findings have broad implications for research on reasoning, language comprehension, and cognitive reflection tests. They suggest that performance on illusion tasks does not necessarily reflect a person’s deliberate abilities, but that sometimes, the correct response can come from an accurate intuition. This refines how scientists interpret what it means to be an “intuitive” versus a “reflective” thinker.

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