This technique has been used a lot in attention studies. At the same time, they have to listen for a faint tone in the background, and respond as soon as they hear it. This tells us something about how similar the different sounds are to one another. All of these are examples of ways of looking at adult speech. High-Amplitude Sucking Paradigm.
Infants learn to suck on a pacifier to receive a stimulus.
If the infant notices the change, they will suck harder. If they start sucking harder, they noticed the difference. That is, that their hearing is such that they can tell those sounds apart. Or, infants hear daba daba - then daga daga. This also can be used to see to what extent infants can generalize.