Help or hindrance: how violation of different assimilation rules affects spoken-language processing

Area of Science:

• Psycholinguistics
• Phonetics
• Cognitive Science

Background:

• Recent research suggests spoken-language processing is inhibited by violations of obligatory assimilation processes in a listener's native language.
• Assimilation, a phonological process, modifies sounds based on adjacent sounds.

Purpose of the Study:

• To investigate how violations of obligatory assimilation processes affect phoneme detection in listeners' native language.
• To determine if the direction of assimilation rules (progressive vs. regressive) influences the effect on phoneme detection.

Main Methods:

• Four phoneme-detection experiments were conducted using native German and Dutch listeners.
• Participants detected target fricatives or stops in nonwords that either followed or violated German assimilation rules (progressive fricative place assimilation, regressive nasal place assimilation).

Main Results:

• German listeners detected target fricatives faster when progressive assimilation was violated, contrary to previous findings.
• This facilitation effect was specific to German listeners and not observed in Dutch listeners.
• When regressive assimilation was violated, German listeners showed slower detection, consistent with prior research.
• The effect was observed in both monosyllabic and bisyllabic nonwords, ruling out syllable structure as an explanation.

Conclusions:

• The direction of assimilation rules influences processing: progressive assimilation violations can facilitate, while regressive assimilation violations inhibit, phoneme detection.
• Facilitation in progressive assimilation may stem from low expectations and novel 'popout' effects.
• Inhibition in regressive assimilation may result from unmet high expectations.