Tonal synchrony in mother–infant interaction based on harmonic and pentatonic series

This study reports the occurrence of ‘tonal synchrony’ as a new dimension of early mother–infant interaction synchrony. The findings are based on a tonal and temporal analysis of vocal interactions between 15 mothers and their 3-month-old infants during 5 min of free-play in a laboratory setting. In total, 558 vocal exchanges were identified and analysed, of which 84% reflected harmonic or pentatonic series. Another 10% of the exchanges contained absolute and/or relative pitch and/or interval imitations. The total durations of dyads being in tonal synchrony were normally distributed (M = 3.71, SD = 2.44). Vocalisations based on harmonic series appeared organised around the major triad, containing significantly more simple frequency ratios (octave, fifth and third) than complex ones (non-major triad tones). Tonal synchrony and its characteristics are discussed in relation to infant-directed speech, communicative musicality, pre-reflective communication and its impact on the quality of early mother–infant interaction and child's development.     

Temporal differentiation of response duration in children of different ages: developmental changes in relations between verbal and nonverbal behavior.

Children aged 4.5, 7, or 11 years received an experimental session in which a contingency was placed on button-press duration. Each discrete trial was followed by a brief verbal probe asking a question about the contingency requirement. Other groups of children received an identical task followed by a postexperimental interview. Level of adaptation to the duration contingency tended to increase with age in subjects receiving posttrial verbal probes, but not for those who were interviewed. Eleven-year-olds in the verbal probe condition showed a strong correlation between accurate temporal differentiation and number of verbalizations relating to response duration or timing. The younger subjects, with one exception, showed no association between timing-related verbalizations (which were almost totally absent) and response duration differentiation. This developmental difference occurred even though the younger subjects verbalized after almost every trial. The results suggest that although 11-year-old children apparently produce rule-governed behavior under verbal control as adults do, the behavior of younger children may be controlled directly by reinforcement contingencies even when their verbal repertoires are highly developed.     

Schedule-induced licking during multiple schedules

Schedule-induced polydipsia was studied in rats bar pressing under two-component multiple schedules of food reinforcement. The first component of the multiple schedule was a variable-interval 1-min schedule throughout the experiment. The schedule comprising the second component was varied over blocks of sessions in terms of rate and magnitude of reinforcement, and was either variable-interval 3-min (one pellet), variable-interval 3-min (three pellets), variable-interval 1-min (one pellet), or extinction. Water intake per session varied with the rate of reinforcement in the schedule comprising the second component and was highest when the schedule was variable-interval 1-min. Both bar-pressing behavior and licking behavior showed behavioral interactions between the two components of the multiple schedules. With magnitude of reinforcement held constant, a matching relationship was observed between lick rate and reinforcement rate; the relative frequency of licks in the constant component matched the relative frequency of reinforcement in that component. Bar pressing, however, showed only a moderate degree of relativity matching. During the schedule-induced licking, a burst of licking followed each delivery of a pellet (post-prandial drinking). The duration of these bursts of licking was observed to be a function of the inter-reinforcement interval.     

Maturation of fetal responses to music

Maturation of fetal response to music was characterized over the last trimester of pregnancy using a 5-minute piano recording of Brahms' Lullaby, played at an average of 95, 100, 105 or 110 dB (A). Within 30 seconds of the onset of the music, the youngest fetuses (28-32 weeks GA) showed a heart rate increase limited to the two highest dB levels; over gestation, the threshold level decreased and a response shift from acceleration to deceleration was observed for the lower dB levels, indicating attention to the stimulus. Over 5 minutes of music, fetuses older than 33 weeks GA showed a sustained increase in heart rate; body movement changes occurred at 35 weeks GA. These findings suggest a change in processing of complex sounds at around 33 weeks GA, with responding limited to the acoustic properties of the signal in younger fetuses but attention playing a role in older fetuses.