Developmental intersensory interference: Augmented prenatal sensory experience interferes with auditory learning in duck embryos.

Embryos experiencing concurrent waterbed stimulation while being exposed to a mallard maternal call failed to learn the call, whereas embryos experiencing alternating waterbed and auditory stimulation did learn the call. However, when embryos were exposed to a lower level of concurrent waterbed stimulation-one that was closer to the normal level of proximal stimulation-they were able to learn the maternal call. Thus, an augmented level of proximal stimulation that departs less significantly from the normal range does not necessarily cause intersensory interference, even if it is higher than normal, suggesting a threshold that must be exceeded to cause interference