Typical phonological analyses of Spanish consider the consonants , , and the underlying phonemes and their corresponding approximants , , and allophonic and derivable by phonological rules. However, approximants may be the more basic form because monolingual Spanish-learning children learn to produce the continuant contrast between and before they do the lead voicing contrast between and . (In comparison, English-learning children are able to produce adult-like voicing contrasts for these stops well before age three.) The allophonic distribution of and produced in adult speech is not learned until after age two and not fully mastered even at age four.