The Cupertino effect is the tendency of a spell checker to suggest or autocorrect inappropriate words to replace misspelled words and words not in its dictionary.
This term refers to the fact that the unhyphenated English word "cooperation" was often changed to "Cupertino" by older spellcheckers with dictionaries containing only the hyphenated variant, "co-operation".[1] Cupertino is the home of Apple Inc., and thus would be in most computer spelling dictionaries.
Cupertino has been present in Microsoft's custom dictionaries since at least 1989 (when Word 4 for Mac was released).[2] Lack of vigilance in post-spellcheck editing can result in even official documents containing phrases like "as well as valuable experience in international Cupertino"[3] and "reinforcing bilateral and multinational Cupertino and assistance actions."[4] Other examples include "South Asian Association for Regional Cupertino" and "presentation on African-German Cupertino."[5]
Benjamin Zimmer of Thinkmap, Inc. and the University of Pennsylvania have collected many examples of similar errors, including the common replacement of "definately" (misspelling of "definitely") with "defiantly," DeMeco Ryans with "Demerol" (in the New York Times), Voldemort with "Voltmeter" (Denver Post), and the Muttahida Qaumi Movement being replaced with "Muttonhead Quail" (Reuters).[5]
The user need not always select an incorrect word for it to appear in the document; in WordPerfect 9 with factory default settings, any unrecognized word that was close enough to exactly one known word was automatically replaced with that word. Smartphones with dictionary supported virtual keyboards automatically replace possible mistakes with dictionary words.[6]