FIGURE 6.3 Categorical perception of speech sounds by infants Infants aged 1 to 4 months were habituated to a tape of artificial speech sounds. (a) One group repeatedly heard a/ba/sound with a VOT of 20, and they gradually habituated to it. (b) When the sound changed to/pa/, with a VOT of 40, they dishabituated, indicating that they perceived the difference between the two sounds, just as adults do. (c) A different group was habituated to a/pa/sound with a VOT of 60. (d) When the sound changed to another/pa/with a VOT of 80, the infants remained habituated, suggesting that, like adults, they did not discriminate between these two sounds. (Adapted from Eimas et al., 1971)