Children's speech perception strategies, together with speech production, start developing from the very beginning of language acquisition. In the case of children exhibiting usual (normal) qualitative and quantitative changes, no dissociation is assumed between speaking and speech processing. However, observational data show that children's speech production may go on working properly for quite some time even if there is some hidden impairment in their speech processing abilities. This usually leads to learning difficulties and restricted cognitive operations. Little is known, furthermore, about the expected age-bound working of speech processing performance or indeed about the line of development and its characteristics. In a series of experiments, the authors have sought answers to a number of questions: (i) What level do the speech perception and comprehension processes under scrutiny reach between ages 4 and 9? (ii) What interrelationships do they exhibit? (iii) Exactly how can the fact of development be pinpointed? Test results of a total of 600 children (altogether over fifty thousand data) have been analysed with respect to speech perception and speech comprehension processes. The results have confirmed a particular cooperation among the individual perceptual processes: development can be accounted for in terms of a decrease of interconnections among various types of processing. The older the child is, the more pronounced the mutual independence of perceptual processes is, and that is what underlies the proper functioning of the whole mechanism.