Ongoing Cues Research Articles

Optimizing song retention through the spacing effect

The spacing effect refers to the improvement in memory retention for materials learned in a series of sessions, as opposed to massing learning in a single session. It has been extensively studied in the domain of verbal learning using word lists. Less evidence is available for connected discourse or tasks requiring the complex coordination of verbal and other domains. In particular, the effect of spacing on the retention of words and music in song has yet to be determined. In this study, university students were taught an unaccompanied two-verse song based on traditional materials to a criterion of 95% correct memory for sung words. Subsequent training sessions were either massed or spaced by two days or one week and tested at a retention interval of three weeks. Performances were evaluated for number of correct and incorrect syllables, number of correctly and incorrectly pitched notes, degree notes were off-pitch, and number of hesitations while singing. The data revealed strong evidence for a spacing effect for song between the massed and spaced conditions at a retention interval of three weeks, and evidence of no difference between the two spaced conditions. These findings suggest that the ongoing cues offered by surface features in the song are strong enough to enable verbatim recall across spaced conditions, as long as the spacing interval reaches a critical threshold.

The impact of peripheral mechanisms on the precedence effect.

When two similar sounds are presented from different locations, with one (the lead) preceding the other (the lag) by a small delay, listeners typically report hearing one sound near the location of the lead sound source-this is called the precedence effect (PE). Several questions about the underlying mechanisms that produce the PE are asked. (1) How might listeners' relative weighting of cues at onset versus ongoing stimulus portions affect perceived lateral position of long-duration lead/lag noise stimuli? (2) What are the factors that influence this weighting? (3) Are the mechanisms invoked to explain the PE for transient stimuli applicable to long-duration stimuli? To answer these questions, lead/lag noise stimuli are presented with a range of durations, onset slopes, and lag-to-lead level ratios over headphones. Monaural, peripheral mechanisms, and binaural cue extraction are modeled to estimate the cues available for determination of perceived laterality. Results showed that all three stimulus manipulations affect the relative weighting of onset and ongoing cues and that mechanisms invoked to explain the PE for transient stimuli are also applicable to the PE, in terms of both onset and ongoing segments of long-duration, lead/lag stimuli.

The Haas Effect—Lateral extent and perceptual weighting of localization cues

The Haas effect is a well-known manifestation of the precedence effect. Originally, Haas measured the echo threshold as a function of the primary auditory event and its single reflection being equally loud. What is not well known is the lateral position of the lead/lag pair as a function of inter-stimulus interval and level difference between lead and lag. How robust the Haas effect is in the localization dominance region was investigated, adjusting the level difference between lead and lag, and using 200 ms band-passed noise presented dichotically over headphones. In addition, the onset and offset cues were removed for half the trials and left intact for the other half to investigate the roles of onset and offset cues versus ongoing cues. Lateral displacement of the auditory event was recorded with an acoustic pointer. Analysis of these results help to reveal the perceptual weighting of localization cues in the Haas effect.

Temporal weighting in binaural hearing: Distinct contributions of interaural time and level differences following sound onset.

The ability of a listener to make use of interaural level differences (ILDs) or envelope interaural time differences (ITDs) carried by modulated high-frequency sounds depends critically on the modulation period. Specifically, periods shorter than 4–5 ms substantially reduce the availability of ongoing cues, with the consequence that localization and discrimination increasingly rely on onset cues as the period decreases. Over the past several years, the authors have studied this dependence by measuring listeners’ detection of dynamic ITD and ILD, their temporal weighting of both cues during localization tasks, and their perception of simulated sources and echoes (i.e., precedence effects) carrying one or both cues. This presentation will review the results of those studies, which suggest that (a) onsets dominate processing of both cues at high rates; (b) postonset ILD sensitivity is better maintained, compared to postonset ITD, at high rates; (c) sensitivity to postonset ILD, but typically not ITD, exhibits a temporally increasing profile consistent with binaural temporal integration of that cue; and (d) maintained sensitivity to postonset ILD allows changes in that cue, but not ITD, to cause “breakdown” of precedence effects. [Work supported by NIH Grant Nos. R03 DC009482 and F31 DC010543, and NSF Grant No. IOB-0630338.]

Interaural time-delay sensitivity in bilateral cochlear implant users: effects of pulse rate, modulation rate, and place of stimulation.

Electrical interaural time delay (ITD) discrimination was measured using 300-ms bursts applied to binaural pitch matched electrodes at basal, mid, and apical locations in each ear. Six bilateral implant users, who had previously shown good ITD sensitivity at a pulse rate of 100 pulses per second (pps), were assessed. Thresholds were measured as a function of pulse rate between 100 and 1,000 Hz, as well as modulation rate over that same range for high-rate pulse trains at 6,000 pps. Results were similar for all three places of stimulation and showed decreasing ITD sensitivity as either pulse rate or modulation rate increased, although the extent of that effect varied across subjects. The results support a model comprising a common ITD mechanism for high- and low-frequency places of stimulation, which, for electrical stimulation, is rate-limited in the same way across electrodes because peripheral temporal responses are largely place invariant. Overall, ITD sensitivity was somewhat better with unmodulated pulse trains than with high-rate pulse trains modulated at matched rates, although comparisons at individual rates showed that difference to be significant only at 300 Hz. Electrodes presenting with the lowest thresholds at 600 Hz were further assessed using bursts with a ramped onset of 10 ms. The slower rise time resulted in decreased performance in four of the listeners, but not in the two best performers, indicating that those two could use ongoing cues at 600 Hz. Performance at each place was also measured using single-pulse stimuli. Comparison of those data with the unmodulated 300-ms burst thresholds showed that on average, the addition of ongoing cues beyond the onset enhanced overall ITD sensitivity at 100 and 300 Hz, but not at 600 Hz. At 1,000 Hz, the added ongoing cues actually decreased performance. That result is attributed to the introduction of ambiguous cues within the physiologically relevant range and increased dichotic firing.

Modeling temporal weighting of interaural time and level differences in high-rate click trains.

Accurate localization of sound sources requires that information be integrated over time and across multiple spatial cues in a manner that reflects the reliability of those cues over time. Several past studies have investigated the relative weighting of multiple cues (e.g., interaural time-intensity “trading”) as well as the temporal weighting applied to brief stimuli such as noise bursts and impulse trains. The results have demonstrated reduced sensitivity to ongoing envelope interaural time differences in high-frequency, high-rate stimuli and a consequent shift in weighting to favor onset and interaural-level cues. The dominance of onset over ongoing cues is consistent with the precedence effect [Wallach et al., Am. J. Psych. 62:315–336 (1949)] and binaural adaptation [Hafter and Dye, J. Acoust. Soc. Am. 73:644–651 (1983)] and may reflect a combination of (1) peripheral auditory factors, (2) effective modulation, (3) postonset inhibition of binaural information, and (4) temporal integration of ongoing cues. In this study, simple mathematical models are used to study the effects of these factors on temporal weighting of interaural time and level differences in narrowband click trains varying in spectral composition, click timing, and cue availability.

Getting Enough: Mother’ Concerns About Breastfeeding a Preterm Infant After Discharge

To describe maternal concerns about breastfeeding a preterm infant in the postdischarge period and to delineate the strategies mothers used in managing these concerns. Naturalistic inquiry was used. A semistructured interview was conducted with the mother in the home 1 month after discharge of the infant. Twenty mothers of preterm infants; the infants had been in a level 3 hospital nursery, and the mothers had received individualized breastfeeding support services in the hospital. Three categories of maternal concerns emerged from the data: adequate milk consumption by infants; milk composition; and problems with the mechanics of breastfeeding a preterm infant. Mothers identified strategies for these concerns. The mothers' main concern was whether infants consumed an adequate volume of milk by breastfeeding alone. Strategies for managing concerns about getting enough included using supplemental and complemental feeding, using ongoing cues to tell that the infant is getting enough, and persevering with breastfeeding. Mothers of preterm infants have unique concerns about breastfeeding in the postdischarge period and need individualized interventions.

A note on onset effects in binaural hearing.

Various definitions of interaural "onset" delays in binaural stimuli have led to discrepant conclusions about the relative strength of onset versus ongoing cues. A distinction is offered here between gating (envelope-onset) delays, and early fine-structure (carrier) delays. This distinction, in conjunction with independent experimental results on the relative effectiveness of interaural envelope and carrier delays, leads to a reconciling interpretation.