when do babies become able to distinguish different speech sounds
Phonological development Infants as young as 1 month perceive some speech sounds as speech categories (they display categorical perception of speech). For example, the sounds /b/ and /p/ differ in the amount of breathiness that follows the opening of the lips. Using a computer generated continuum in breathiness between /b/ and /p/, Eimas et al. (1971) showed that English-learning infants paid more attention to differences near the boundary between /b/ and /p/ than to equal-sized differences within the /b/-category or within the /p/-category.[4] Their measure, monitoring infant sucking-rate, became a major experimental method for studying infant speech perception.
Peekaboo Peekaboo is thought by developmental psychologists to demonstrate an infant's inability to understand object permanence.[2] Object permanence is an important stage of cognitive development for infants. In early sensorimotor stages, the infant is completely unable to comprehend object permanence. Psychologist Jean Piaget conducted experiments with infants which led him to conclude that this awareness was typically achieved at eight to nine months of age.[citation needed] Infants before this age are too young to understand object permanence. A lack of object permanence can lead to A-not-B errors, where children reach for a thing at a place where it should not be.