The ability to detect amplitude modulation (AM) is essential to distinguish the spectro-temporal
features of speech from those of a competing masker. Previous work shows that AM sensitivity
improves until 10 years of age. This may relate to the development of sensory factors (tuning of
AM filters, susceptibility to AM masking) or to changes in processing efficiency (reduction in internal noise, optimization of decision strategies). To disentangle these hypotheses, three groups of
children (5–11 years) and one of young adults completed psychophysical tasks measuring thresholds for detecting sinusoidal AM (with a rate of 4, 8, or 32 Hz) applied to carriers whose inherent
modulations exerted different amounts of AM masking. Results showed that between 5 and 11
years, AM detection thresholds improved and that susceptibility to AM masking slightly increased.
However, the effects of AM rate and carrier were not associated with age, suggesting that sensory
factors are mature by 5 years. Subsequent modelling indicated that reducing internal noise by a factor 10 accounted for the observed developmental trends. Finally, children’s consonant identification
thresholds in noise related to some extent to AM sensitivity. Increased efficiency in AM detection
may support better use of temporal information in speech during childhood