This study traces the development of interrogative structures in a single c
hild from the first word combinations to age 3;8. It confirms earlier findi
ngs that child usage is highly formulaic and goes on to tackle the crucial
issue of how children progress from rote-learned formulas to adult-like pro
ductivity. It is argued that this is accomplished by analyzing formulas and
extracting constructional schemas from them. Constructional schemas are pa
rtly underspecified symbolic units; unlike the abstract rules of formal lin
guistics, they are derived from actual expressions and have the same struct
ure as their instantiations. They emerge spontaneously when the learner has
acquired a sizeable repertoire of formulas. Their original function is to
allow more efficient storage; but, once extracted, they are also available
for the construction of novel expressions.