Gradient perception of geminate consonants in Arabic: a perceptual study of durational thresholds

• Natural speech stimuli with geminates shortened in 10 ms increments. • Stops needed less duration reduction than fricatives or sonorants. • Geminates heard as singletons even above actual singleton duration. • Stops showed abrupt shifts; fricatives and sonorants changed gradually. • Segment-specific thresholds define geminate vs. singleton perception. This study examines how native Arabic listeners perceive geminate consonants that have been systematically shortened, aiming to identify the durational threshold at which a geminate is no longer heard as such and is instead perceived as a singleton consonant. Twenty Najdi Arabic speakers listened to Arabic words with geminate consonants, where the geminate portion was gradually shortened in 10 ms increments. Listeners indicated whether each modified token sounded like the original geminate word or its singleton counterpart. Results revealed no single durational threshold; instead, thresholds varied across consonants. Stop consonants were perceived as singletons after relatively smaller reductions, whereas fricatives and sonorants required greater shortening. Listeners often began identifying a geminate as a singleton even while its duration remained longer than a typical singleton consonant. These findings indicate that geminate perception in Arabic is gradient and segment-specific. They support the view that geminates are not merely lengthened singletons but represent distinct durational categories shaped by consonant-specific cues.