In transformational grammar, a trace is an empty (phonologically null) category that occupies a position in the syntactic structure. In some theories of syntax, traces are used in the account of constructions such as wh-movement and passive. Traces are important theoretical devices in some approaches to syntax.
Evidence for traces
Empirical evidence pointing to the existence of traces, independently of all theory-specific considerations, has also been presented in the literature. For example, for many English speakers, the contraction of want to to wanna is possible in some contexts, but not in others:
- Who does Vicky want to vote for t? → Who does Vicky wanna vote for?
- Who does Vicky want t to win? → *Who does Vicky wanna win?
One way to explain this contrast is to assume that the trace left behind by the extraction of who in the second example blocks the contraction of want and to.
The statement "Vicky wants Peter to win" is transformed into an 'echo'-question. If "who" is moved to the beginning of the sentence, it will leave a trace. The existence of the trace will make it impossible to contract "want" and "to". Consider the following:
However, the validity of this and similar arguments have been called into question by linguists favoring non-transformational approaches.[who?]
Principles that regulate traces
In government and binding theory, traces are subject to the empty category principle (ECP), which states that all traces must be "properly governed". Proper government is either theta-government or antecedent-government:
- Who did John say that Mary saw t? (The verb "see" both governs and theta-marks the trace, so the trace is theta-governed.)
- Who t said that? (The wh-word governs the trace and is coindexed with it, so the trace is antecedent-governed.)
However, intermediate traces are not subject to the ECP because they are deleted at LF (logical form).
- Sag, Ivan A., and Janet Dean Fodor (1994). "Extraction without Traces". In Raul Aranovich, William Byrne, Susanne Preuss, and Martha Senturia (eds), Proceedings of the Thirteenth West Coast Conference on Formal Linguistics. Stanford, CA: CSLI Publications, pp. 365–384.