Recent studies have shown that many subject-verb agreement errors consist o
f making the verb agree with the immediately preceding noun, as in "The sme
ll of the rubbish-bins are foul". Assuming that it is the automaticity of t
he agreement operation which is responsible for these attraction errors in
expert writers, the present studies aimed at demonstrating the gradual auto
matization of this operation in young writers by examining developmental ch
anges in the occurrence of agreement errors. In three experiments we found
that subjects' performance moves from systematic errors in number agreement
in young children (e.g., no use of plural marks) to attraction errors in f
ifth graders and older adults through an intermediate phase characterized b
y an attention-demanding and easily disrupted computation of verb agreement
displayed by some second graders. Attraction errors are a byproduct of the
automatization of the implementation of the agreement process.