Moses illusions, fast and slow

When asked “How many animals of each kind did Moses take on the Ark?”, most people answer “Two”, failing to notice that it was Noah, and not Moses, who took the animals in the Ark. “Fast-and-slow” dual process accounts of such semantic illusions posit that incorrect responders are not sensitive to their error and that overcoming the illusion requires deliberate correction of an intuitive erroneous answer. We present three experiments that force us to revise this dual process view. We used a two-response paradigm in which participants had to give their first, initial answer under cognitive load and time pressure. Next, participants could take all the time they wanted to deliberate and select a final answer. This enabled us to identify the intuitively generated response that preceded the final response given after deliberation. Results show that participants do not necessarily need to deliberate to avoid the illusion and that incorrect respondents consistently display error sensitivity (as reflected in decreased confidence), even when deliberation is minimized. Both reasoning performance and error sensitivity in the initial, intuitive stage tended to be driven by the semantic relatedness between the anomalous word (e.g., “Moses”) and the undistorted word (e.g., “Noah”). We show how this leads to a revised model where the response to semantic illusions depends on the interplay of both incorrect and correct intuitions.