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Infants' localization of sounds within hemifields: estimates of minimum audible angle
1Department of Psychology, University of Western Ontario, London, Canada.
Insights
Infants
Area of Science:
- Auditory Neuroscience
- Developmental Psychology
- Speech and Hearing Sciences
Background:
- Sound localization is crucial for auditory development.
- Understanding how infants perceive auditory space informs developmental trajectories.
- Previous research suggests better sound localization near the midline.
Purpose of the Study:
- To investigate infants' ability to localize sounds in their hemifields.
- To determine the minimum audible angle (MAA) in infants at different ages.
- To compare hemifield localization acuity with midline localization acuity.
Main Methods:
- A Go/No-Go conditioned head-turn procedure was used.
- Infants aged 6, 12, and 18 months were tested.
- Sound shifts were presented at 60 degrees off midline, and discrimination thresholds were measured.
Main Results:
- Infants' sound localization acuity in hemifields was relatively poor.
- Localization acuity improved significantly with age from 6 to 18 months.
- Minimum audible angle (MAA) estimates were higher (poorer acuity) in hemifields compared to midline.
Conclusions:
- Infants demonstrate poorer sound localization in hemifields than near the midline.
- Auditory space is partitioned more finely near the midline in infants.
- Findings support developmental models of auditory processing and sound localization.
Abstract:
Infants' acuity in localizing sounds within hemifields was examined by determining the smallest sound shift off 60 degrees and along the horizontal axis that infants could discriminate reliably, that is, minimum audible angle (MAA). Infants 6, 12, and 18 months of age were tested using a Go/No-Go conditioned head-turn procedure in which infants received an equal number of no-change (control) trials and sound-shift (experimental) trials. A correct response (i.e., a head turn toward the loud-speakers) on an experimental trial resulted in visual reinforcement. Localization acuity for sounds within hemifields was fairly poor and improved systematically with increasing age. MAA estimates at each age were significantly higher, indicating poorer localization acuity, in comparison to those obtained previously in research examining infants' resolution of auditory space near midline. These findings are consistent with adult data and demonstrate a finer partitioning of auditory space near midline than within hemifields. The implications of these findings for our understanding of the development of auditory processing mechanisms in sound localization are discussed.