Individual differences and age effects in a dichotic informational masking paradigm

Area of Science:

• Auditory perception
• Speech processing
• Psychoacoustics

Background:

• Informational masking (IM) is a key factor limiting speech understanding in noise.
• Previous research primarily focused on ipsilateral maskers, with less known about contralateral masker effects, especially across development.

Purpose of the Study:

• To investigate the impact of contralateral speech maskers on speech understanding in normally-hearing listeners across a wide age range (5-61 years).
• To quantify age-related differences in informational masking (IM) caused by contralateral speech maskers.

Main Methods:

• Participants completed a monaural speech understanding task with ipsilateral speech-spectrum noise.
• Contralateral maskers (modulated noise, male/female speech) were introduced at a fixed level to assess IM.
• Psychometric functions were used to determine the target/masker ratio for 51% correct performance, serving as the baseline threshold.

Main Results:

• Contralateral modulated noise produced no IM across all ages.
• Contralateral speech maskers produced significant IM, with children (5-8 years) showing up to 20 dB, while adults showed only 4 dB.
• Male and female contralateral speech maskers yielded comparable IM, unlike findings with ipsilateral maskers.

Conclusions:

• Contralateral speech maskers significantly impact speech understanding, particularly in young children, indicating developmental differences in auditory processing.
• The mechanisms underlying IM from contralateral and ipsilateral speech maskers may differ, suggesting distinct neural pathways or processing strategies.
• Findings highlight the importance of considering masker location and listener age when assessing speech intelligibility in complex auditory environments.