In the early months of life, infants acquire information about the phonetic properties of their native language simply by listening to adults speak. The acoustic properties of phonetic units in language input to young infants in the United States, Russia, and Sweden were examined. In all three countries, mothers addressing their infants produced acoustically more extreme vowels than they did when addressing adults, resulting in a "stretching" of vowel space. The findings show that language input to infants provides exceptionally well-specified information about the linguistic units that form the building blocks for words.

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An important role in development of speech and language belongs to the threshold characteristics of auditory sensitivity as well as to the degree of maturation of central mechanisms of auditory processing. The ability of differentiation of sounds, analysis of temporal characteristics and the level of intelligence affect the development of speech skills. A comprehensive assessment of auditory perception and cognitive development was conducted in two groups of preschool children aged 4.5 to 6 years. The main group consisted of 10 children with permanent bilateral sensorineural hearing loss, all of them were experienced users of hearing aids; 10 children with normal hearing were included in the control group. All children underwent psychophysical testing (whisper test, repetition of “quasi-words”, identification of speech signals with similar acoustic characteristics, pairs of consonants “z-s”, “p-t”, “g-k”); acoustical analysis of speech samples with the reproduction of speech from hearing; assessment of non-verbal intelligence (by means of the Raven’s Colored Progressive Matrices). The obtained results indicate significant differences in the characteristics of the acoustic analysis of speech signals of children with normal hearing and hearing impairments, no significant differences have been observed in non-verbal intelligence characteristics of children in these groups. Besides, the children with hearing loss have high fatigability. These data may indicate the symptoms of central auditory processing disorders in hearing impaired children. To identify these problems it is necessary to use psychophysical tests and specialized questionnaires.

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