Grammatische Illusionen  Lokal wohlgeformt  global deviant * HUBERT HAIDER Abstract Grammatical illusions are linguistic equivalents of optical illusions in visual processing. A grammatical illusion amounts to an expression that is judged acceptable in spite of its grammatical deviance. It is the hitherto insuffi- ciently appreciated fourth “aggregate state”, that completes the set of four logical pairings of the properties “(un-)grammatical” and “(un-)accep- table”. A typical source of syntactic illusions is the mental processor’s attempt to repair grammatical inconsistencies resulting from contradicting require- ments of syntactic regularities. The resulting pseudo-solutions tend to be appraised as acceptable, although they remain patently ungrammatical. The consequences of this phenomenon, when acknowledged, are evident: Acceptability turns out to be neither a necessary nor a sufficient property of a grammatical construction. The attempt of modeling any construction that is (introspectively) judged acceptable as grammatically well-formed is tantamount to the attempt of devising a grammatical derivation for con- structions of arbitrary (un)grammaticality. Informant consultation results are contaminated and of limited value. Syntactic investigations (and se- mantic ones as well) deserve more reliable standards of data assessment than mere sampling of self-perception testimonies and corpus search. Keywords: grammatical illusions, syntactic illusions, acceptability, gram- maticality, IPP construction, parasitic morphology 1. Einleitung Grammatische Illusionen sind im sprachlichen Bereich das, was im Be- reich der visuellen Verarbeitung optische Illusionen sind. Das Bemer- * Besondere Dankbarkeit empfinde ich den beiden Gutachter/inne/n gegenüber, für deren außergewöhnlich hilfreiche, weil äußerst genaue und detaillierte sowie kritisch-unter- Zeitschrift für Sprachwissenschaft 30 (2011), 223-257 0721-9067/2011/030-0223 DOI 10.1515/ZFSW.2011.009  Walter de Gruyter AUTHOR’S COPY | AUTORENEXEMPLAR AUTHOR’S COPY | AUTORENEXEMPLAR