Spectral versus spectrotemporal modulation detection by children: A preliminary investigation

Basic and applied studies of spectral resolution often apply a phase shift to modulated stimuli, creating spectrotemporal modulation, to ensure variation of the location of spectral peaks. This procedure results in acoustic signals with dynamic spectral structure. A general developmental phenomenon is that immature sensory systems prefer signal change (i.e., dynamic structure) over static signals, and findings involving speech perception specifically show that children initially attend more to dynamic spectral structure and less to static spectral structure compared to adults. In this preliminary investigation, we tested the prediction that young children with poor sensitivity to static spectral modulation, as indexed by detection thresholds, would show better sensitivity to dynamic spectral structure. Accordingly, 5–6 year olds who came to the laboratory to be tested on spectral modulation detection using static signals (that had starting phase randomized) were subsequently tested on signals with a dynamic phase shift, if they did not demonstrate thresholds better than the initial maximum depth. Most of these children (70%) demonstrated reliable thresholds for the dynamic signals, even though they could not do so for the static signals. These results suggest that at least for children, testing with spectrotemporal modulation may overestimate spectral resolution.