It has been observed that when-questions are one of the last
wh-questions produced by children learning English either as a first
language (L1) or as a second language (L2). Explanations proposed for the late
appearance of when-questions in L1 acquisition have been mostly based on
cognitive factors. However, the cognition-based approach to when-questions
faces problems in explaining L2 acquisition data, which show that L2 children who
are cognitively more mature than L1 children follow the same developmental sequence.
In this paper, I propose a possible explanation based on internal linguistic
factors. According to Enç (1987), tense is a referential expression and
temporal adverbials are antecedents of tense. I develop Enç's
theory further and propose that in a when-question, tense is a bound
variable, which is bound by the quantificational interrogative when. Thus,
in order to produce when-questions, children must be at a stage where they
understand bound variable readings. According to Roeper and de Villiers (1991),
English-speaking children learn a bound variable reading approximately after 36
months, and the learning continues through the kindergarten years. The age at which
a bound variable reading first appears corresponds to the point at which
when-questions begin to occur. I propose that the complexity of the
interaction between the quantificational when and tense, a bound variable,
causes the delayed production of when-questions in developing grammars.