liberman et al. found that no 4-year-olds and only 17% of 5-year-olds were able to tap out the number of phonemes (individual sounds) in a word. 70% of 6-year-olds were able to do so. this might mean that children are aware of syllables as units of speech early on, while they don't show awareness of individual phonemes until school age. another explanation is that individual sounds do not easily translate into beats, which makes clapping individual phonemes a much more difficult task than clapping syllables. one reason why phoneme awareness gets much better once children start school is because learning to read provides a visual aid as how to break up words into their smaller constituents.