Figure 1.

Experimental procedure. Pregnant women (n = 34) were asked to tape two different nursery rhymes and were afterward randomly assigned to two groups. The experimental group (EG, n = 23) replayed one rhyme (80 dB over speakers; twice a day for five minutes) from week 34 of gestation until birth (i.e., up to ~42 days). The control group (CG, n = 11) did not replay any rhyme. Two and five weeks after birth infants’ electrocardiography (ECG) and high density electroencephalography (hdEEG) were recorded during baseline (silence) and auditory stimulation periods with both rhymes, each presented with the maternal and an unfamiliar female voice.