The Moses (Semantic) Illusion: Definition and Examples in Grammar

Glossary of Grammatical and Rhetorical Terms

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In pragmatics and psycholinguistics, the Moses illusion is a phenomenon whereby listeners or readers fail to recognize an inaccuracy or inconsistency in a text. It is also called the semantic illusion.

The Moses illusion (also known as semantic illusion) was first identified by T.D. Erickson and M.E. Mattson in their article "From Words to Meaning: A Semantic Illusion" (Journal of Verbal Learning and Verbal Behavior, 1981).

Examples and Observations

"The Moses illusion occurs when people answer 'two' to the question 'How many animals of each kind did Moses take on the ark?' even though they know that Noah was the one with the ark. A number of different hypotheses have been proposed to explain this effect."
(E. Bruce Goldstein, Cognitive Psychology: Connecting Mind, Research, and Everyday Experience, 2nd ed. Thomson Wadsworth, 2008)

"The Economic and Social Research Council (ESRC) finds we may not be processing every word see hear or read. . . .

"[T]ry this: 'Can a man marry his widow’s sister?'

"According to the study, most people answer in the affirmative, not realizing they’re agreeing that a dead man can marry his bereaved wife’s sister.

"This has something to do with what are known as semantic illusions.

"These are words that may fit the general context of a sentence, even though they don’t actually make sense. They can challenge traditional methods of language processing, which assumes we develop our understanding of a sentence by thoroughly weighing the meaning of each word.

"Instead, the researchers found these semantic illusions show that, rather than listening and analyzing each word, our language processing is based only on shallow and incomplete interpretations of what we hear or read. . . .

"Looking at the EEG patterns of volunteers who read or listened to sentences containing semantic anomalies, researchers found that when volunteers were tricked by the semantic illusion, their brains had not even noticed the unusual words." (Economic and Social Research Council, "What They Say, and What You Hear, Can Differ." Voice of America: Science World, July 17, 2012)

Ways of Reducing the Moses Illusion

"[S]tudies have shown that at least two factors contribute to the likelihood that an individual comprehender will experience the Moses illusion. First, if the anomalous word shares aspects of meaning with the intended word, the likelihood of experiencing a Moses illusion increases. For example, Moses and Noah are pretty close in meaning in many people's understanding of the terms--they are both older, male, bearded, serious Old Testament characters. When more distinctive characters are introduced into the scenario--Adam, for example--the strength of the Moses illusion is greatly reduced...

"Another way to reduce the Moses illusion and to make it more likely that the comprehenders will detect the anomaly is to use linguistic cues to focus attention on the intruding item. Syntactic structures such as clefts (like 16) and there-insertions (like 17) offer ways to do this.

(16) It was Moses who took two of each kind of animal on the Ark.
(17) There was a guy called Moses who took two of each kind of animal on the Ark.

When attention is focused on Moses using these kinds of grammatical cues, subjects are more likely to notice that he does not fit in with the great flood scenario, and they are less likely to experience the Moses illusion." (Matthew J. Traxler, Introduction to Psycholinguistics: Understanding Language Science. Wiley-Blackwell, 2012)

"All the research on the Moses illusion makes it clear that people can find distortions, but find this difficult if the distorted element is semantically related to the theme of the sentence. The odds of noticing the distortion are reduced by increasing the number of elements that need some kind of match (lowering the odds that the distorted element will be in focus). . . . Every day, at many levels, we accept slight distortions without noticing them. We notice some and ignore them, but many we do not even realize occur." (Eleen N. Kamas and Lynne M. Reder, "The Role of Familiarity in Cognitive Processing." Sources of Coherence in Reading, ed. by Robert F. Lorch and Edward J. O'Brien. Lawrence Erlbaum, 1995)

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Nordquist, Richard. "The Moses (Semantic) Illusion: Definition and Examples in Grammar." ThoughtCo, Aug. 27, 2020, Nordquist, Richard. (2020, August 27). The Moses (Semantic) Illusion: Definition and Examples in Grammar. Retrieved from Nordquist, Richard. "The Moses (Semantic) Illusion: Definition and Examples in Grammar." ThoughtCo. (accessed February 5, 2023).