It is an unanswered question how specific the cries of the human neonate may be, although some mothers are confident they can distinguish different types of cries from their infants.
One method of answering such a question would be to record a sample of the cries of a neonate during its first week. Then, at moments when the infant was not crying, subject it to a distributed series of playbacks of its past cries, and record the fresh crying which the infant emitted in response to hearing itself cry. The infant should cry to the sound of its own cry, since the cry is a quite contagious response. One could then examine the degree of correlation between each cry which was used as a stimulus and the contagious response to that cry. If the neonate does emit distinctively different cries, then it should respond differentially to its own distinctive cries; therefore the variance between pairs of cries should exceed that within pairs of cries. To our knowledge such a test method has not yet been employed.(7-8)
Frings and Jumber tape-recorded the distress cries of a starling which it uttered when caught. They then played this at high volume over a loudspeaker in a town where there were many starlings. The effect was to drive the starlings away permanently.-Silvan Tomkins, Affect, Imagery, Consciousness
There are also distress cries of birds which have exactly the opposite effect on the parent bird who hears them. In species of birds in which the mother does no feeding, the cries of the infant birds bring the mother and prevent their getting lost.
The extraordinary specificity of such responses was shown in a study by Bruckner who found that the domestic hen responds only to the sound of the distress call of the chick. When he fastened a chick to a peg behind a screen, the mother would come to its rescue when she heard the chick crying. But when he put the chick under a glass dome so that the mother cuold see it struggling but could not hear its distress cry, she was entirely indifferent.(15-16)